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1. Design and performance of the prototype Schwarzschild-Couder telescope camera

Author: Colin B. Adams, Giovanni Ambrosi, Michelangelo Ambrosio, Carla Aramo, Timothy Arlen, Wystan Benbow, Bruna Bertucci, Elisabetta Bissaldi, Jonathan Biteau, Massimiliano Bitossi, Alfonso Boiano, Carmela Bonavolontà, Richard Bose, Aurelien Bouvier, Mario Buscemi, Aryeh Brill, Anthony M. Brown, James H. Buckley, Rodolfo Canestrari, Massimo Capasso, Mirco Caprai, Paolo Coppi, Corbin E. Covault, Davide Depaoli, Leonardo Di Venere, Manel Errando, Stephan Fegan, Qi Feng, Emanuele Fiandrini, Amy Furniss, Markus Garczarczyk, Alasdair Gent, Nicola Giglietto, Francesco Giordano, Enrico Giro, Robert Halliday, Olivier Hervet, Gareth Hughes, Simone Incardona, Thomas B. Humensky, Maria Ionica, Weidong Jin, Caitlin A. Johnson, David Kieda, Frank Krennrich, Andrey Kuznetsov, Jon Lapington, Francesco Licciulli, Serena Loporchio, Giovanni Marsella, Vincenzo Masone, Kevin Meagher, Thomas Meures, Brent A. W. Mode, Samuel A. I. Mognet, Reshmi Mukherjee, Akira Okumura, Francesca R. Pantaleo, Riccardo Paoletti, Federico Di Pierro, Deivid Ribeiro, Luca Riitano, Emmet Roache, Duncan Ross, Julien Rousselle, Andrea Rugliancich, Marcos Santander, Michael Schneider, Harm Schoorlemmer, Ruo-Yu Shang, Brandon Stevenson, Leonardo Stiaccini, Hiroyasu Tajima, Leslie P. Taylor, Julian Thornhill, Luca Tosti, Giovanni Tripodo, Valerio Vagelli, Massimo Valentino, Justin Vandenbroucke, Vladimir V. Vassiliev, Scott P. Wakely, Jason J. Watson, Richard White, Patrick Wilcox, David A. Williams, Matthew Wood, Peter Yu, Adrian Zink, Adams C.B., Ambrosi G., Ambrosio M., Aramo C., Arlen T., Benbow W., Bertucci B., Bissaldi E., Biteau J., Bitossi M., Boiano A., Bonavolonta C., Bose R., Bouvier A., Buscemi M., Brill A., Brown A.M., Buckley J.H., Canestrari R., Capasso M., Caprai M., Coppi P., Covault C.E., Depaoli D., Di Venere L., Errando M., Fegan S., Feng Q., Fiandrini E., Furniss A., Garczarczyk M., Gent A., Giglietto N., Giordano F., Giro E., Halliday R., Hervet O., Hughes G., Incardona S., Humensky T.B., Ionica M., Jin W., Johnson C.A., Kieda D., Krennrich F., Kuznetsov A., Lapington J., Licciulli F., Loporchio S., Marsella G., Masone V., Meagher K., Meures T., Mode B.A.W., Mognet S.A.I., Mukherjee R., Okumura A., Pantaleo F.R., Paoletti R., Di Pierro F., Ribeiro D., Riitano L., Roache E., Ross D., Rousselle J., Rugliancich A., Santander M., Schneider M., Schoorlemmer H., Shang R.-Y., Stevenson B., Stiaccini L., Tajima H., Taylor L.P., Thornhill J., Tosti L., Tripodo G., Vagelli V., Valentino M., Vandenbroucke J., Vassiliev V.V., Wakely S.P., Watson J.J., White R., Wilcox P., Williams D.A., Wood M., Yu P., and Zink A.
Subjects: imaging atmospheric Cherenkov telescopes, instrumentation, Physics - Instrumentation and Detectors, very-high-energy gamma-ray astronomy, Physics::Instrumentation and Detectors, Mechanical Engineering, Settore FIS/01 - Fisica Sperimentale, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Instrumentation and Detectors (physics.ins-det), Electronic, Optical and Magnetic Materials, Cherenkov telescope array, Space and Planetary Science, Control and Systems Engineering, ddc:530, prototype Schwarzschild-Couder telescope, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), silicon photomultipliers
Abstract: Journal of astronomical telescopes, instruments, and systems 8(01), 014007-1 (2022). doi:10.1117/1.JATIS.8.1.014007, The prototype Schwarzschild-Couder Telescope (pSCT) is a candidate for a medium-sized telescope in the Cherenkov Telescope Array. The pSCT is based on a novel dual mirror optics design which reduces the plate scale and allows for the use of silicon photomultipliers as photodetectors. The prototype pSCT camera currently has only the central sector instrumented with 25 camera modules (1600 pixels), providing a 2.68$^{\circ}$ field of view (FoV). The camera electronics are based on custom TARGET (TeV array readout with GSa/s sampling and event trigger) application specific integrated circuits. Field programmable gate arrays sample incoming signals at a gigasample per second. A single backplane provides camera-wide triggers. An upgrade of the pSCT camera is in progress, which will fully populate the focal plane. This will increase the number of pixels to 11,328, the number of backplanes to 9, and the FoV to 8.04$^{\circ}$. Here we give a detailed description of the pSCT camera, including the basic concept, mechanical design, detectors, electronics, current status and first light., Published by SPIE, [Bellingham, Wash.]
Published: 2022
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2. Detection of the Crab Nebula by the prototype Schwarzschild-Couder Telescope

Author: G. Pareschi, Manel Errando, Corbin Covault, F. Di Pierro, S. I. Mognet, V. Masone, N. Giglietto, D. B. Kieda, L. Di Venere, E. Roache, M. Ambrosio, Julien Rousselle, Justin Vandenbroucke, D. Ribeiro, N. Otte, Maria Ionica, Alasdair E. Gent, F. R. Pantaleo, Enrico Giro, A. Boiano, K. Meagher, Serena Loporchio, E. Fiandrini, H. Tajima, Valerio Vagelli, Atsushi Okumura, Marcos Santander, B. A. W. Mode, Luca Tosti, S. Incardona, L. P. Taylor, E. Pueschel, G. Ambrosi, David A. Williams, M. Capasso, V. V. Vassiliev, M. Bitossi, P. I. Batista, Bruna Bertucci, J. H. Buckley, A. Brill, A. M. Brown, G. Tripodo, W. Jin, G. Marsella, Wystan Benbow, C. Bonavolontà, S. J. Fegan, Richard Bose, R. Shang, D. Depaoli, R. Paoletti, Jamie Holder, Rodolfo Canestrari, F. Licciulli, Andrea Rugliancich, Thomas Meures, M. Valentino, Amy Furniss, Olivier Hervet, C. B. Adams, Carla Aramo, R. A. Cameron, Q. Feng, T. B. Humensky, Elisabetta Bissaldi, L. Stiaccini, A. Zink, Reshmi Mukherjee, G. H. Tovmassian, L. Riitano, Ferdinando Giordano, R. Halliday, and M. Caprai
Subjects: astro-ph.HE, High Energy Astrophysical Phenomena (astro-ph.HE), Pixel, business.industry, Computer science, FOS: Physical sciences, Field of view, Cherenkov Telescope Array, law.invention, Telescope, Crab Nebula, Silicon photomultiplier, Optics, law, Observatory, Angular resolution, business, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, astro-ph.IM, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract: The Schwarzschild-Couder Telescope (SCT) is a medium-sized telescope technology proposed for the Cherenkov Telescope Array. It uses a novel dual-mirror optical design that removes comatic aberrations across its entire field of view. The SCT camera employs high-resolution silicon photomultiplier (SiPM) sensors with a pixel size of 4 arcminutes. A prototype SCT (pSCT) has been constructed at the Fred Lawrence Whipple Observatory in Arizona, USA. An observing campaign in 2020, with a partial camera of 1600 pixels (2.7 degrees by 2.7 degrees field of view) resulted in detection of the Crab Nebula at 8.6 sigma statistical significance. Work on the pSCT camera and optical system is ongoing to improve performance and prepare for an upcoming camera upgrade. The pSCT camera upgrade will replace the current camera modules with improved SiPMs and readout electronics and will expand the camera to its full design field of view of 8 degrees in diameter (11,328 pixels). The fully upgraded pSCT will enable next-generation very-high-energy gamma-ray astrophysics through excellent background rejection and angular resolution. In this presentation we describe first results from the successful operation of the pSCT and future plans., 9 pages, 3 figures, 2 tables, contribution to ICRC 2021, similar to 10.1016/j.astropartphys.2021.102562 (arXiv:2012.08448)
Published: 2021

3. Identifying muon rings in VERITAS data using convolutional neural networks trained on images classified with Muon Hunters 2

Author: Matthew Lundy, A. Brill, M. Capasso, Hugh Dickinson, Manel Errando, T. J. Williamson, S. Kumar, S. Patel, Vladimir Vassiliev, M. J. Lang, David Hanna, P. Moriarty, John L. Quinn, Orel Gueta, donggeun tak, David A. Williams, Michael Laraia, Sameer Patel, Jodi Christiansen, P. Wilcox, Thomas Brian Humensky, C. E. McGrath, Alasdair E. Gent, R.R. Prado, Avery Archer, K. Ragan, M. Kertzman, C. Adams, M. Nievas-Rosillo, J. H. Buckley, Reshmi Mukherjee, David Kieda, Tobias Kleiner, A. J. Chromey, A. D. Falcone, Philip Kaaret, James M. Ryan, Wystan Benbow, Lucy Fortson, A. N. Otte, R. A. Ong, C. Giuri, K. A. Farrell, G. M. Foote, Deivid Ribeiro, Stephen Serjeant, E. Roache, Martin Pohl, Binita Hona, Jamie Holder, G. H. Sembroski, Daniel Nieto, K. Pfrang, S. O'Brien, Kevin Flanagan, Amanda Weinstein, Gary Gillanders, Marcos Santander, Q. Feng, I. Sadeh, Darryl Wright, R. Shang, W. Jin, Olivier Hervet, Gernot Maier, P. T. Reynolds, Amy Furniss, and E. Pueschel
Subjects: Muon, Physics::Instrumentation and Detectors, Calibration (statistics), Computer science, business.industry, Pattern recognition, Convolutional neural network, law.invention, Image (mathematics), Hough transform, Telescope, Identification (information), law, Computer Science::Computer Vision and Pattern Recognition, False positive paradox, High Energy Physics::Experiment, Artificial intelligence, business
Abstract: Muons from extensive air showers appear as rings in images taken with imaging atmospheric Cherenkov telescopes, such as VERITAS. These muon-ring images are used for the calibration of the VERITAS telescopes, however the calibration accuracy can be improved with a more efficient muon-identification algorithm. Convolutional neural networks (CNNs) are used in many state-of-the-art image-recognition systems and are ideal for muon image identification, once trained on a suitable dataset with labels for muon images. However, by training a CNN on a dataset labelled by existing algorithms, the performance of the CNN would be limited by the suboptimal muon-identification efficiency of the original algorithms. Muon Hunters 2 is a citizen science project that asks users to label grids of VERITAS telescope images, stating which images contain muon rings. Each image is labelled 10 times by independent volunteers, and the votes are aggregated and used to assign a `muon' or `non-muon' label to the corresponding image. An analysis was performed using an expert-labelled dataset in order to determine the optimal vote percentage cut-offs for assigning labels to each image for CNN training. This was optimised so as to identify as many muon images as possible while avoiding false positives. The performance of this model greatly improves on existing muon identification algorithms, identifying approximately 30 times the number of muon images identified by the current algorithm implemented in VEGAS (VERITAS Gamma-ray Analysis Suite), and roughly 2.5 times the number identified by the Hough transform method, along with significantly outperforming a CNN trained on VEGAS-labelled data.
Published: 2021
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4. TeV and optical observations of the Be/pulsar binary 1A0535+262 during the 2020 giant outburst

Author: Matthew Lundy, Massimo Capasso, Rene Ong, Iftach Sadeh, Philip Kaaret, Weidong Jin, Wystan Benbow, Reshmi Mukherjee, Raul Prado, Sameer Patel, Patrick Moriarty, Gernot Maier, Amy Furniss, Ken Ragan, David Williams, James Buckley, Lucy Fortson, John Quinn, Jamie Holder, Chiara Giuri, Elisa Pueschel, Daniel Nieto, Colin Adams, Stephan O'Brien, Deivid Ribeiro, Konstantin Pfrang, Orel Gueta, Gregory M Foote, Amanda Weinstein, Sajan Kumar, Tyler Williamson, Donggeun Tak, Conor McGrath, Tobias Kai Kleiner, Martin Pohl, Paul Reynolds, Binita Hona, David Hanna, Marcos Santander, Glenn Sembroski, Sonal Ramesh Patel, Manel Errando, Mary Kertzman, Olivier Hervet, Mireia Nievas-Rosillo, Mark Lang, Emmet Roache, Thomas Brian Humensky, Ruo-Yu Shang, Vladimir Vassiliev, Alisha Chromey, Abe Falcone, Jodi Christiansen, Adam Otte, Alasdair E. Gent, Aryeh Brill, James Ryan, Kayla Farrell, Gary Gillanders, Qi Feng, Avery Archer, and David Kieda
Subjects: Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, Gamma ray, Astrophysics::Instrumentation and Methods for Astrophysics, Binary number, FOS: Physical sciences, Cosmic ray, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Binary pulsar, law.invention, Pulsar, law, Astrophysics - High Energy Astrophysical Phenomena, Cherenkov radiation, Flare
Abstract: 1A 0535+262 is a Be X-ray binary pulsar and one of the only galactic pulsar systems to show radio jet emission. Characterizing the very high energy emission (VHE, >100 GeV) in these extreme microquasars is critical to understanding their contribution to the origin of galactic cosmic rays. The 2020 giant outburst of this system, where X-ray fluxes exceeded 12 Crab, marked a rare opportunity to investigate the gamma-ray and rapid optical variability of these transient systems while in such an extreme state. This month of activity marked the brightest flare measured in this system. VERITAS's developing optical capabilities in tandem with the ability to measure TeV gamma rays allowed for a unique campaign to be undertaken. VERITAS's observations of this system during the outburst will be presented in the context of observations at lower energies and previous observations of this system by imaging atmospheric Cherenkov telescopes.
Published: 2021

5. Gamma-ray and Optical Observations of Repeating Fast Radio Bursts with VERITAS

Author: Matthew Lundy, Massimo Capasso, Rene Ong, Iftach Sadeh, Philip Kaaret, Weidong Jin, Wystan Benbow, Reshmi Mukherjee, Raul Prado, Sameer Patel, Patrick Moriarty, Gernot Maier, Amy Furniss, Ken Ragan, David Williams, James Buckley, Lucy Fortson, John Quinn, Jamie Holder, Chiara Giuri, Elisa Pueschel, Daniel Nieto, Colin Adams, Stephan O'Brien, Deivid Ribeiro, Konstantin Pfrang, Orel Gueta, Gregory M Foote, Amanda Weinstein, Sajan Kumar, Tyler Williamson, Donggeun Tak, Conor McGrath, Tobias Kai Kleiner, Martin Pohl, Paul Reynolds, Binita Hona, David Hanna, Marcos Santander, Glenn Sembroski, Sonal Ramesh Patel, Manel Errando, Mary Kertzman, Olivier Hervet, Mireia Nievas-Rosillo, Mark Lang, Emmet Roache, Thomas Brian Humensky, Ruo-Yu Shang, Vladimir Vassiliev, Alisha Chromey, Abe Falcone, Jodi Christiansen, Adam Otte, Alasdair E. Gent, Aryeh Brill, James Ryan, Kayla Farrell, Gary Gillanders, Qi Feng, Avery Archer, and David Kieda
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Millisecond, Fast radio burst, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Gamma ray, Theoretical models, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Magnetar, Radio telescope, Rapid rise, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Fast radio burst (FRBs) are an exciting class of bright, extragalactic, millisecond radio transients. The recent development of large field-of-view (FOV) radio telescopes has caused a rapid rise in the number of identified single burst and repeating FRBs. This has allowed for the extensive multi-wavelength follow-up to search for the potential counterparts predicted by theoretical models. New observations of similar radio transients in Galactic magnetars like SGR 1935+2154 have continued to motivate the search for rapid optical and very-high-energy (VHE, >100 GeV) counterparts. Since 2016 VERITAS has engaged in an FRB observing campaign to search for the prompt optical, and VHE emission from multiple repeating FRBs. We present these new results from VERITAS observations of five repeating sources including data taken simultaneously with bursts observed by the CHIME radio telescope.
Published: 2021
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6. Multi-Messenger observations of the Fermi-LAT blazar 4FGL J0658.6+0636 consistent with an IceCube high-energy neutrino

Author: David R. Williams, Antoine Kouchner, K. A. Farrell, Alasdair E. Gent, V. V. Vassiliev, Fabian Schüssler, H. A. Peña-Herazo, Georgios Paraschos, R. Shang, D. S. Hanna, Q. Feng, John L. Quinn, D. Ribeiro, Daniel Nieto, A. Brill, Giacomo Bonnoli, M. Kertzman, Lucy Fortson, Yong Sheng, Olivier Hervet, T. B. Humensky, Francesco Massaro, S. O'Brien, Alessio Berti, M. J. Lang, donggeun tak, Teddy Cheung, Suvi Gezari, Joern Wilms, A. D. Falcone, P. T. Reynolds, Miguel Perez-Torres, Andrea Tramacere, Reshmi Mukherjee, G. M. Foote, Binita Hona, C. Giuri, Raniere de Menezes, P. Kaaret, I. Sadeh, Frank J. Masci, Emilio Fernandez-Garcia, W. Jin, Wystan Benbow, Uwe Bach, R. R. Prado, P. Moriarty, Jonas Heßdörfer, M. Pohl, Matthias Kadler, Steven Hämmerich, Gernot Maier, G. H. Sembroski, Andrea Gokus, R. A. Ong, M. Capasso, Ivan Agudo, Marcos Santander, C. E. McGrath, T. J. Williamson, A. J.R. Weinstein, E. Roache, A. Archer, Jorge Otero-Santos, Simone Garrappa, Alex Kraus, G. H. Gillanders, A. J. Castro-Tirado, Alexis Coleiro, Jodi Christiansen, Jamie Holder, K. Ragan, Meenakshi Rajagopal, A. N. Otte, Alessandro Paggi, K. Pfrang, Orel Gueta, Marcello Giroletti, Cristina Nanci, Javier Moldon, M. Nievas-Rosillo, Elisa Bernardini, C. Adams, Werner Colmar, Y. D. Hu, J. A. Ryan, Richard Walters, M. Lundy, Florian Eppel, Tobias Kleiner, R. Sanchez-Ramirez, J. H. Buckley, A. J. Chromey, Amy Furniss, Charlotte Ward, Konstancja Satalecka, E. Pueschel, Manel Errando, Sara Buson, S. Kumar, S. Patel, M. D. Caballero-Garcia, and Marco Ajello
Subjects: Physics, High energy, Astrophysics, Neutrino, Blazar, Fermi Gamma-ray Space Telescope
Published: 2021
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7. VERITAS Observations of the Galactic Center Region at Multi-TeV Gamma-Ray Energies

Author: S. O'Brien, donggeun tak, E. Roache, K. A. Farrell, V. V. Vassiliev, John L. Quinn, D. Ribeiro, J. H. Buckley, K. Ragan, P. Kaaret, A. Archer, A. J. Chromey, M. Nievas-Rosillo, G. H. Gillanders, Reshmi Mukherjee, David Kieda, Jodi Christiansen, C. Giuri, James M. Ryan, M. Kertzman, Olivier Hervet, Amy Furniss, A. Brill, I. Sadeh, Lucy Fortson, Marcos Santander, Binita Hona, D. S. Hanna, M. J. Lang, E. Pueschel, Wystan Benbow, A. D. Falcone, Orel Gueta, Q. Feng, P. Moriarty, M. Capasso, W. Jin, Daniel Nieto, Gernot Maier, Martin Pohl, T. J. Williamson, A. N. Otte, C. E. McGrath, K. Pfrang, A. J.R. Weinstein, R. Shang, P. T. Reynolds, G. M. Foote, Jamie Holder, R. A. Ong, R. R. Prado, David A. Williams, Tobias Kleiner, G. H. Sembroski, J. A. Ryan, M. Lundy, C. Adams, T. B. Humensky, Manel Errando, S. Kumar, S. Patel, and Alasdair E. Gent
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Supermassive black hole, Astrophysics::High Energy Astrophysical Phenomena, Galactic Center, Astrophysics::Instrumentation and Methods for Astrophysics, Gamma ray, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Light curve, law.invention, Telescope, Sagittarius A, law, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics, Cherenkov radiation, Zenith
Abstract: The Galactic Center region hosts a variety of powerful astronomical sources and rare astrophysical processes that emit a large flux of non-thermal radiation. We present the analysis of the very-high-energy gamma-ray emission above 2 TeV of the region around the Galactic Center known as the Central Molecular Zone using 125 hours of data taken with the VERITAS imaging-atmospheric Cherenkov telescope between 2010 and 2018. This analysis employs new shower reconstruction algorithms and instrument response functions optimized for data taken at large zenith angles such as the Galactic Center sources. We report positions and spectra for point sources VER J1745-290, G0.9+0.1, and HESS J1746-285, along with a light curve for VER J1745-290, the brightest source in the region consistent with the position of the supermassive black hole Sagittarius A*. We also measure the spectrum of the diffuse emission from the Galactic Center ridge region, which has been claimed as evidence of a Galactic PeVatron., Contribution to the Proceedings of the 37th International Cosmic Ray Conference (ICRC 2021), Berlin, Germany
Published: 2021
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8. Status of the VERITAS Stellar Intensity Interferometry (VSII) System

Author: P. Moriarty, Alasdair E. Gent, James Ryan, R. Shang, Daniel Nieto, E. Roache, M. Capasso, M. Kertzman, T. J. Williamson, Davis Jonathan, David R. Williams, K. Ragan, S. O'Brien, Wystan Benbow, M. J. Lang, Marcos Santander, P. Kaaret, M. Pohl, Reshmi Mukherjee, C. E. McGrath, I. Sadeh, A. Brill, K Matthews Nolan, A. J.R. Weinstein, Jamie Holder, C. Giuri, Q. Feng, John L. Quinn, A. Archer, D. Ribeiro, M. Nievas-Rosillo, Sameer Patel, Orel Gueta, A. D. Falcone, Manel Errando, G. H. Sembroski, Gernot Maier, S. Kumar, R. R. Prado, D. S. Hanna, C. B. Adams, David Kieda, T. B. Humensky, S. Patel, LeBohec Tugdual, R. A. Ong, G. H. Gillanders, Olivier Hervet, K. A. Farrell, V. V. Vassiliev, Lisa Mike, Lucy Fortson, Jodi Christiansen, Tobias Kleiner, G. M. Foote, J. H. Buckley, A. J. Chromey, donggeun tak, A. N. Otte, K. Pfrang, W. Jin, M. Lundy, Binita Hona, Amy Furniss, E. Pueschel, and P. T. Reynolds
Subjects: Physics, Interferometry, Astronomy, Intensity (physics)
Published: 2021
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9. Very High Energy Gamma-ray Emission from the Binary System LS I +61 303

Author: G. M. Foote, S. O'Brien, W. Jin, Tobias Kleiner, R. Shang, Orel Gueta, R. R. Prado, P. Kaaret, P. T. Reynolds, E. Pueschel, John L. Quinn, I. Sadeh, C. B. Adams, James Ryan, D. Ribeiro, David R. Williams, M. Pohl, Gernot Maier, Jodi Christiansen, Q. Feng, T. B. Humensky, M. Lundy, Marcos Santander, Lucy Fortson, P. Moriarty, Olivier Hervet, C. E. McGrath, M. Capasso, M. Kertzman, A. J.R. Weinstein, A. Brill, A. N. Otte, Daniel Nieto, David Kieda, T. J. Williamson, K. Pfrang, Manel Errando, S. Kumar, R. A. Ong, S. Patel, G. H. Sembroski, J. H. Buckley, M. Nievas-Rosillo, Binita Hona, D. S. Hanna, K. A. Farrell, V. V. Vassiliev, Sameer Patel, donggeun tak, Amy Furniss, A. Archer, E. Roache, A. J. Chromey, G. H. Gillanders, Reshmi Mukherjee, C. Giuri, Alasdair E. Gent, K. Ragan, M. J. Lang, A. D. Falcone, Jamie Holder, and Wystan Benbow
Subjects: Physics, High energy, Gamma ray, Binary system, Computational physics
Published: 2021
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10. The VERITAS-Stellar Intensity Interferometry (VSII) survey of Stellar Diameters

Author: James Ryan, Wystan Benbow, Mike Lisa, G. M. Foote, P. Moriarty, C. B. Adams, Lucy Fortson, Amy Furniss, Q. Feng, R. A. Ong, P. T. Reynolds, M. Capasso, M. Kertzman, Manel Errando, E. Pueschel, Orel Gueta, Daniel Nieto, T. J. Williamson, S. Kumar, T. B. Humensky, M. Nievas-Rosillo, G. H. Sembroski, S. Patel, Nolan Matthews, Sameer Patel, Alasdair E. Gent, J. H. Buckley, A. N. Otte, D. S. Hanna, Marcos Santander, M. Lundy, Tugdual LeBohec, P. Kaaret, A. Archer, K. Pfrang, Gernot Maier, A. J. Chromey, S. O'Brien, Binita Hona, C. E. McGrath, donggeun tak, Olivier Hervet, David R. Williams, Reshmi Mukherjee, A. Brill, G. H. Gillanders, A. J.R. Weinstein, Jonathan Davis, Jodi Christiansen, I. Sadeh, C. Giuri, R. Shang, Tobias Kleiner, E. Roache, David Kieda, M. Pohl, K. Ragan, K. A. Farrell, V. V. Vassiliev, John L. Quinn, D. Ribeiro, R. R. Prado, W. Jin, Jamie Holder, M. J. Lang, and A. D. Falcone
Subjects: Telescope, Physics, Interferometry, Stars, Cardinal point, Optical wavelength, law, IACT, Astrophysics, Cherenkov radiation, Intensity (physics), law.invention
Abstract: The VERITAS Imaging Air Cherenkov Telescope (IACT) array was augmented in 2019 with high-speed focal plane electronics to allow its use for Stellar Intensity Interferometry (SII) observations. Since January 2019, The VERITAS Stellar Interferometer (VSII) recorded more than 250 hours of moonlit observations on 39 different bright stars and binary systems ($m_V < 3.74$ ) at an effective optical wavelength of 416 nm. These observations resulted in the measurement of the diameters of several stars with better than 5\% resolution. This talk will describe the status of the VSII survey and analysis.
Published: 2021
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11. Detection of the Crab Nebula with the 9.7 m prototype Schwarzschild-Couder telescope

Author: Gagik Tovmassian, F. Di Pierro, V. Masone, M. Ambrosio, C. B. Adams, N. La Palombara, A. Brill, Amy Furniss, K. Meagher, Marcos Santander, Nicola Giglietto, Olivier Hervet, Wystan Benbow, C. Bonavolontà, S. I. Mognet, Maria Ionica, A. Bouvier, S. P. Wakely, Vladimir Vassiliev, F. R. Pantaleo, Fernando Garfias, Alasdair E. Gent, Akira Okumura, S. Loporchio, A. Kuznetsov, J. Thornhill, J. H. Buckley, R. A. Cameron, L. Stiaccini, E. Fiandrini, E. Pueschel, S. Schlenstedt, R. J. White, L. Di Venere, Thomas Meures, G. Ambrosi, Arturo Iriarte, Daniel Nieto, M. Valentino, Riccardo Paoletti, Q. Feng, S. J. Fegan, A. Boiano, V. J. Guarino, David Kieda, G. Hughes, Julien Rousselle, G. Sironi, Justin Vandenbroucke, V. Vagelli, R. Shang, Enrico Giro, B. A. W. Mode, T. B. Humensky, A. Petrashyk, W. Jin, Maria Magdalena González, N. Otte, M. Caprai, Stefan Funk, M. Bitossi, D. Ribeiro, Karen Byrum, B. Bertucci, G. Pareschi, Andrea Rugliancich, Manel Errando, D. Depaoli, E. Roache, J. Ruíz-Díaz-Soto, T. C. Arlen, Michael Schneider, Jason John Watson, T. Nguyen, B. Stevenson, Jonathan Biteau, L. Tosti, Reshmi Mukherjee, David A. Williams, Jonathan S. Lapington, P. Kaaret, C. A. Johnson, Elisabetta Bissaldi, Gordon T. Richards, P. Fortin, Carla Aramo, Francesco Giordano, Salvo Scuderi, G. M. Foote, Hiroyasu Tajima, Richard Bose, Jamie Holder, R. Halliday, P. Yu, Rodolfo Canestrari, Ruben Alfaro, D. Ross, A. Zink, P. Wilcox, P. I. Batista, Matthew Wood, P. T. Reynolds, B. Kim, F. Licciulli, L. P. Taylor, A. M. Brown, M. Capasso, Corbin Covault, Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire Leprince-Ringuet (LLR), and Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)
Subjects: Cherenkov Telescope Array, Physics::Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Field of view, 01 natural sciences, law.invention, Telescope, Primary mirror, law, Observatory, pixel, 0103 physical sciences, optical, Astrophysics::Solar and Stellar Astrophysics, photomultiplier: silicon, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], mirror, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Cherenkov radiation, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, resolution, Astronomy and Astrophysics, radiation: Cherenkov, aberration, cascade, observatory, Crab Nebula, gamma ray: emission, cosmic radiation, atmosphere, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], statistical
Abstract: The Schwarzschild-Couder Telescope (SCT) is a telescope concept proposed for the Cherenkov Telescope Array. It employs a dual-mirror optical design to remove comatic aberrations over an $8^{\circ}$ field of view, and a high-density silicon photomultiplier camera (with a pixel resolution of 4 arcmin) to record Cherenkov emission from cosmic ray and gamma-ray initiated particle cascades in the atmosphere. The prototype SCT (pSCT), comprising a 9.7 m diameter primary mirror and a partially instrumented camera with 1536 pixels, has been constructed at the Fred Lawrence Whipple Observatory. The telescope was inaugurated in January 2019, with commissioning continuing throughout 2019. We describe the first campaign of observations with the pSCT, conducted in January and February of 2020, and demonstrate the detection of gamma-ray emission from the Crab Nebula with a statistical significance of $8.6\sigma$., Comment: 13 pages, 12 figures, 3 tables, submitted to Astroparticle Physics
Published: 2021
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12. Technical and scientific performance of the prototype Schwarzschild-Couder Telescope for CTA

Author: Mirco Caprai, Olivier Hervet, Robert Halliday, Giovanni Pareschi, Qi Feng, Massimo Capasso, Richard G. Bose, Peter Y. Yu, Daniel Nieto, Luca Tosti, L. P. Taylor, Hiroyasu Tajima, Samuel A. Mognet, Maria Ionica, Wystan Benbow, David Kieda, Julien Rousselle, Francesca R. Pantaleo, Corbin Covault, Massimo Valentino, Vincenzo Masone, Leonardo Di Venere, Rodolfo Canestrari, Massimiliano Bitossi, Andrea Rugliancich, Gagik Tovmassian, Jamie Holder, D. Ross, Leonardo Stiaccini, Enrico Giro, Emanuale Fiandrini, Riccardo Paoletti, Pedro I. Batista, Giovanni Ambrosi, Valerio Vagelli, Carla Aramo, Richard White, Simone Incardona, Federico Di Pierro, Anthony M. Brown, Francesco Giordano, Nicola Giglietto, A. Zink, Ruo-Yu Shang, K. Meagher, Jason J. Watson, J. H. Buckley, N. Otte, B. A. W. Mode, Bruna Bertucci, Thomas Meures, Marcos Santander, Michelangelo Ambrosio, Vladimir V. Vassiliev, Luca Riitano, Reshmi Mukherjee, Stephen Fegan, W. Jin, Alfonso Boiano, Colin B. Adams, Akira Okumura, Justin Vanderbrouke, Carmela Bonavolontà, Giovanni Tripodo, Manel Errando, David A. Williams, A. Brill, E. Roache, D. Ribeiro, Giovanni Marsella, Francesco Licciulli, Elisa Pueschel, Elisabetta Bissaldi, Davide Depaoli, Thomas B. Humensky, Amy Furniss, Serena Loporchio, and Alasdair E. Gent
Subjects: Physics::Instrumentation and Detectors, Computer science, business.industry, Astrophysics::High Energy Astrophysical Phenomena, Gamma rays, Astrophysics::Instrumentation and Methods for Astrophysics, Imaging Cherenkov telescopes, Silicon photomultipliers, Field of view, Cherenkov Telescope Array, law.invention, Telescope, Cardinal point, Upgrade, Optics, Silicon photomultiplier, Crab Nebula, Observatory, law, Schwarzschild-Couder telescope, Astrophysics::Solar and Stellar Astrophysics, Aplanatic optical system, business
Abstract: The Cherenkov Telescope Array (CTA) is the next-generation ground-based observatory for very-high-energy gamma rays. One candidate design for CTA's medium-sized telescopes consists of the Schwarzschild-Couder Telescope (SCT), featuring innovative dual-mirror optics. The SCT project has built and is currently operating a 9.7-m prototype SCT (pSCT) at the Fred Lawrence Whipple Observatory (FLWO); such optical design enables the use of a compact camera with state-of-the art silicon photomultiplier detectors. A partially-equipped camera has recently successfully detected the Crab Nebula with a statistical significance of 8.6 standard deviations. A funded upgrade of the pSCT focal plane sensors and electronics is currently ongoing, which will bring the total number of channels from 1600 to 11328 and the telescope field of view from about 2.7° to 8° . In this work, we will describe the technical and scientific performance of the pSCT.
Published: 2021

13. VERITAS Observations of the Galactic Center Region at Multi-TeV Gamma-Ray Energies

Author: G. H. Sembroski, M. Lundy, P. Moriarty, Lucy Fortson, T. B. Humensky, S. Schlenstedt, Martin Pohl, Gernot Maier, Alasdair E. Gent, M. K. Daniel, Manel Errando, S. P. Wakely, A. Weinstein, J. P. Finley, Reshmi Mukherjee, M. Kertzman, C. Giuri, Jodi Christiansen, K. Ragan, Robert Brose, P. Kaaret, A. N. Otte, A. D. Falcone, K. Pfrang, Marcos Santander, D. S. Hanna, R. Shang, Wystan Benbow, David Kieda, G. H. Gillanders, Olivier Hervet, R. R. Prado, M. Buchovecky, John L. Quinn, D. Ribeiro, S. O'Brien, E. Roache, David A. Williams, R. A. Ong, S. Kumar, A. Brill, Daniel Nieto, Q. Feng, Amy Furniss, James Ryan, F. Krennrich, P. T. Reynolds, M. Nievas-Rosillo, E. Pueschel, B. Stevenson, A. J. Chromey, C. B. Adams, G. Hughes, Jamie Holder, M. J. Lang, Gordon T. Richards, N. Kelley-Hoskins, W. Jin, and M. Capasso
Subjects: 010504 meteorology & atmospheric sciences, accelerator, High-energy astronomy, Astrophysics::High Energy Astrophysical Phenomena, atmosphere [Cherenkov counter], VHE [gamma ray], FOS: Physical sciences, Cosmic ray, Astrophysics, power spectrum, 01 natural sciences, emission [gamma ray], HESS, 0103 physical sciences, supernova, black hole, TeV, cloud, composite, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Supermassive black hole, Spectral index, background, Galactic Center, Gamma ray, Astronomy and Astrophysics, Light curve, flux, Supernova, 13. Climate action, Space and Planetary Science, cosmic radiation, ddc:520, VERITAS, galaxy, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Galactic Center (GC) region hosts a variety of powerful astronomical sources and rare astrophysical processes that emit a large flux of non-thermal radiation. The inner 375 pc x 600 pc region, called the Central Molecular Zone, is home to the supermassive black hole Sagittarius A*, massive cloud complexes, and particle accelerators such as supernova remnants. We present the results of our improved analysis of the very-high-energy (VHE) gamma-ray emission above 2 TeV from the GC using 125 hours of data taken with the VERITAS imaging-atmospheric Cherenkov telescope between 2010 and 2018. The central source VER J1745-290, consistent with the position of Sagittarius A*, is detected at a significance of 38 standard deviations above the background level $(38\sigma)$, and we report its spectrum and light curve. Its differential spectrum is consistent with a power law with exponential cutoff, with a spectral index of $2.12^{+0.22}_{-0.17}$, a flux normalization at 5.3 TeV of $1.27^{+0.22}_{-0.23}\times 10^{-13}$ TeV-1 cm-2 s-1, and cutoff energy of $10.0^{+4.0}_{-2.0}$ TeV. We also present results on the diffuse emission near the GC, obtained by combining data from multiple regions along the GC ridge which yield a cumulative significance of $9.5\sigma$. The diffuse GC ridge spectrum is best fit by a power law with a hard index of 2.19 $\pm$ 0.20, showing no evidence of a cutoff up to 40 TeV. This strengthens the evidence for a potential accelerator of PeV cosmic rays being present in the GC. We also provide spectra of the other sources in our field of view with significant detections, composite supernova remnant G0.9+0.1 and HESS J1746-285., Comment: 19 pages, 8 figures, Accepted for publication in Astrophysical Journal
Published: 2021
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14. VERITAS follow-up observation of the blazar TXS 0506+056

Author: Weidong Jin, RileyAnne Sharpe, Massimo Capasso, Rene Ong, Iftach Sadeh, Philip Kaaret, Wystan Benbow, Reshmi Mukherjee, Raul Prado, Matthew Lundy, Sameer Patel, Patrick Moriarty, Gernot Maier, Amy Furniss, Ken Ragan, David Williams, James Buckley, Lucy Fortson, John Quinn, Jamie Holder, Chiara Giuri, Elisa Pueschel, Daniel Nieto, Colin Adams, Stephan O'Brien, Deivid Ribeiro, Konstantin Pfrang, Orel Gueta, Gregory M Foote, Amanda Weinstein, Sajan Kumar, Tyler Williamson, Donggeun Tak, Conor McGrath, Tobias Kai Kleiner, Martin Pohl, Paul Reynolds, Binita Hona, David Hanna, Marcos Santander, Glenn Sembroski, Sonal Ramesh Patel, Manel Errando, Mary Kertzman, Olivier Hervet, Mireia Nievas-Rosillo, Mark Lang, Emmet Roache, Thomas Brian Humensky, Ruo-Yu Shang, Vladimir Vassiliev, Alisha Chromey, Abe Falcone, Jodi Christiansen, Adam Otte, Alasdair E. Gent, Aryeh Brill, James Ryan, Kayla Farrell, Gary Gillanders, Qi Feng, Avery Archer, and David Kieda
Subjects: Physics, High Energy Astrophysical Phenomena (astro-ph.HE), High energy, Astrophysics::High Energy Astrophysical Phenomena, Flux, FOS: Physical sciences, Cosmic ray, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 13. Climate action, Observatory, QUIET, Neutrino, Astrophysics - High Energy Astrophysical Phenomena, Blazar, Event (particle physics)
Abstract: The gamma-ray blazar TXS 0506+056 was found with an enhanced gamma-ray emission state in spatial and temporal coincidence with the IceCube high energy neutrino event IC170922A. This is the most significant association by far between a high-energy neutrino event and a blazar in a flaring state. Studying the time evolution and spectral behavior of the blazar emission may help in identifying the sources of the diffuse neutrino flux observed by IceCube and the origin of energetic cosmic rays. TXS 0506+056 was detected by the VERITAS gamma-ray observatory with a significance of 5.8 standard deviations above 110 GeV in a 35 hour data set collected between September 23, 2017 and February 6, 2018. Here we will present results from recent VERITAS observations and an associated multiwavelength campaign, collected between October 10, 2018 to March 1, 2021. A relatively quiet very high energy gamma-ray emission state was observed during this time period, and flux upper limits are used to constrain the potential variability of this blazar.
Published: 2021
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15. Prototype Schwarzschild-Couder Telescope for the Cherenkov Telescope Array: Commissioning the Optical System

Author: M. Valentino, M. Capasso, R. A. Cameron, Q. Feng, Valerio Vagelli, L. P. Taylor, Daniel Nieto, K. Meagher, F. R. Pantaleo, N. Otte, F. Di Pierro, V. Masone, R. Shang, F. Licciulli, W. Jin, T. B. Humensky, R. Halliday, Andrea Rugliancich, P. I. Batista, Bruna Bertucci, Wystan Benbow, C. Bonavolontà, Serena Loporchio, L. Stiaccini, A. Boiano, D. Depaoli, R. Paoletti, G. Marsella, A. Brill, Maria Ionica, David R. Williams, Olivier Hervet, B. A. W. Mode, Richard Bose, Corbin Covault, M. Ambrosio, Carla Aramo, M. Caprai, Luca Tosti, Thomas Meures, Peter Y. Yu, E. Roache, Reshmi Mukherjee, N. Giglietto, Rodolfo Canestrari, V. V. Vassiliev, Elisabetta Bissaldi, G. Ambrosi, G. H. Tovmassian, L. Riitano, Marcos Santander, Ferdinando Giordano, E. Pueschel, D. Ribeiro, G. Tripodo, S. J. Fegan, Amy Furniss, G. Pareschi, Manel Errando, S. I. Mognet, Alasdair E. Gent, E. Fiandrini, S. Incardona, D. B. Kieda, J. Vandenbroucke, Julien Rousselle, Enrico Giro, J. H. Buckley, M. Bitossi, C. Adams, Atsushi Okumura, and L. Di Venere
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy, Cherenkov Telescope Array, law.invention, Telescope, law, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Instrumentation and Methods for Astrophysics (astro-ph.IM), Schwarzschild radius, Physics - Optics, Optics (physics.optics)
Abstract: A prototype Schwarzschild-Couder Telescope (pSCT) has been constructed at the Fred Lawrence Whipple Observatory as a candidate for the medium-sized telescopes of the Cherenkov Telescope Array Observatory (CTAO). CTAO is currently entering early construction phase of the project and once completed it will vastly improve very high energy gamma-ray detection component in multi-wavelength and multi-messenger observations due to significantly improved sensitivity, angular resolution and field of view comparing to the current generation of the ground-based gamma-ray observatories H.E.S.S., MAGIC and VERITAS. The pSCT uses a dual aspheric mirror design with a $9.7$ m primary mirror and $5.4$ m secondary mirror, both of which are segmented. The Schwarzschild-Couder (SC) optical system (OS) selected for the prototype telescope achieves wide field of view of $8$ degrees and simultaneously reduces the focal plane plate scale allowing an unprecedented compact ($0.78$m diameter) implementation of the high-resolution camera ($6$mm/ $0.067$deg per imaging pixel with $11,328$ pixels) based on the silicon photo-multipliers (SiPMs). The OS of the telescope is designed to eliminate spherical and comatic aberrations and minimize astigmatism to radically improve off-axis imaging and consequently angular resolution across all the field of view with respect to the conventional single-mirror telescopes. Fast and high imaging resolution OS of the pSCT comes with the challenging submillimeter-precision custom alignment system, which was successfully demonstrated with an on-axis point spread function (PSF) of $2.9$ arcmin prior to the first-light detection of the Crab Nebula in 2020. Ongoing and future commissioning activities are reported.
Published: 2021

16. Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign

Author: Masanori Nakamura, R. Shang, Abelardo Moralejo, A. Rugliancich, Marina Manganaro, Jun Liu, Monika Moscibrodzka, Andreas Specovius, V. Ramakrishnan, S. O'Brien, Michal Ostrowski, Luis C. Ho, Sera Markoff, D. Depaoli, I. Jung-Richardt, Manel Errando, Chiara Righi, S. Panny, Toshiaki Inada, Alexandra J. Tetarenko, Daniela Dorner, Norbert Wex, Nimesh A. Patel, Olivier Hervet, C. Arcaro, Alasdair E. Gent, Yu Wun Wong, Gaia Vanzo, Pierre Brun, Konstancja Satalecka, Stefan Funk, Lorenzo Bellizzi, Michael Lindqvist, Michele Doro, Felix Jankowsky, P. Kaaret, Nicholas R. MacDonald, Lang Cui, P. Temnikov, S. Patel, Sabrina Einecke, Manuel Artero, E. Moretti, Hope Boyce, M. Gaug, Charles F. Gammie, Iryna Lypova, Gisela N. Ortiz-León, Felix Aharonian, Colin J. Lonsdale, Buell T. Jannuzi, Gavin Rowell, M. Bryan, Yvonne Becherini, Aleksandar Popstefanija, M. Pohl, A. Marcowith, Jean-Pierre Ernenwein, H. Alyson Ford, Wystan Benbow, Karen E. Williamson, Daryl Haggard, Hambeleleni Ndiyavala, Tod R. Lauer, Arnaud Mares, Chaitanya Priyadarshi, Michael Punch, Helge Rottmann, J. Zorn, D. Dominis Prester, Bernd Schleicher, M. Minev, Hector Olivares, Ciriaco Goddi, S. Pita, J. Herrera, Alessia Spolon, Léa Jouvin, Na Wang, G. Martí-Devesa, Tomohiko Oka, Kirsty Feijen, E. Do Souto Espiñeira, Ralph Eatough, Johannes Veh, Stefano Gabici, Tomislav Terzić, D. Glawion, Gilles Fontaine, Bradford Benson, C. B. Rulten, Jenni Jormanainen, Jason SooHoo, Michael Titus, Jose Miguel Delgado, Marcos López-Moya, Freek Roelofs, Wlodek Bednarek, M. Lundy, Richard Anantua, Alessandra Lamastra, P. T. Reynolds, Vassil Verguilov, M. Lemoine-Goumard, G. Fichet de Clairfontaine, L. Di Venere, Michael Kreter, Jose Miguel Miranda, Alan L. Roy, Yating Chai, A. López-Oramas, M. Tluczykont, Jacek Niemiec, R. Konno, Tyler Trent, Olaf Reimer, Heino Falcke, Amanpreet Kaur, M. Panter, Narek Sahakyan, Kasper B. Schmidt, A. Carosi, K. Egberts, L. Maraschi, Stefan Cikota, V. Joshi, Koji Noda, Elisa Bernardini, Ye-Fei Yuan, Garrett K. Keating, Fumie Tazaki, Pawel Gliwny, M. Vazquez Acosta, Nicola Giglietto, M. Capasso, Vincent Piétu, Satoshi Fukami, Roman Gold, Elina Lindfors, Satoki Matsushita, A. Lemiere, F. Eichhorn, U. Katz, Yoshinori Yonekura, N. Shafi, Natalia Żywucka, Michael Kramer, M. Palatiello, Daniel Mazin, Samuel Timothy Spencer, Victoria Moreno, Oliver Porth, Julian Sitarek, Kazi L.J. Rygl, Wen Ping Lo, Geoffrey C. Bower, Ilje Cho, S. Fegan, Samuel Zouari, J. M. Paredes, V. Fallah Ramazani, Thomas Murach, Jim Hinton, R. J. White, F. Leone, S. Loporchio, M. de Naurois, Ed Fomalont, Bart Ripperda, Dominique Broguiere, J. Becerra González, Joseph R. Farah, Q. Feng, Andreas Quirrenbach, Taehyun Jung, C. Trichard, Masahiro Teshima, Domenico Tiziani, D. Malyshev, Richard Plambeck, Lynn D. Matthews, Avery E. Broderick, S. Kumar, T. J. Williamson, M. K. Daniel, Sylvia Zhu, P. J. Meintjes, Tjark Miener, Jodi Christiansen, Roger Brissenden, S. Sailer, Dmitry Khangulyan, David Paneque, Thomas P. Krichbaum, Sergey S. Savchenko, Angelo Ricarte, Riaan Steenkamp, T. Chand, J. Dyks, Francesco Dazzi, V. Baghmanyan, Zorawar Wadiasingh, Kazunori Akiyama, Stefan Ohm, C. Levy, Giovanna Ferrara, Makoto Inoue, Jhilik Majumdar, Nobuyuki Sakai, Dieter Horns, Jorge A. Preciado-López, Cornelia Müller, G. Hermann, Regis Terrier, A. J. Chromey, Dominic W. Pesce, Felix M. Pötzl, Mark Gurwell, Alejandro Cruz-Osorio, Ivan Marti-Vidal, Ben Prather, Tom Armstrong, Jongho Park, Matteo Cerruti, Ziri Younsi, Amy Furniss, Chih-Wei Locutus Huang, Lijing Shao, A. Djannati-Ataï, Shoko Koyama, D. Gottschall, P. Vincent, A. Brill, Kenji Toma, Antonios Nathanail, M. Nievas-Rosillo, M. Seglar-Arroyo, C. Delgado Mendez, Mahito Sasada, G. Busetto, Maciek Wielgus, Marcos Santander, Doosoo Yoon, D. A. Sanchez, Hiroki Okino, Christo Venter, Christiaan D. Brinkerink, James Ryan, S. Mićanović, Raquel Fraga-Encinas, Mark G. Rawlings, G. H. Sembroski, G. Principe, Xiang Liu, Karl Friedrich Schuster, Ronald Hesper, L. Sun, Ciro Bigongiari, Ramesh Narayan, M. Strzys, L. Mohrmann, Daniel R. van Rossum, Y. Ohtani, Wu Jiang, Luciano Rezzolla, Nu. Komin, V. A. Acciari, Katherine L. Bouman, Jürgen Besenrieder, Clemens Hoischen, A. A. Zdziarski, Antonio Tutone, Hung Yi Pu, A. Arbet Engels, J.-P. Lenain, A. De Angelis, Tomoya Hirota, R. J. García López, Carlo Romoli, Werner Hofmann, Tuomas Savolainen, Neil M. Nagar, Minfeng Gu, M. Karjalainen, Vitaly Neustroev, A. N. Otte, John F. C. Wardle, Tomoaki Oyama, Jongsoo Kim, Monica Barnard, J. Otero-Santos, R. D. Parsons, Pierre Christian, A. Priyana Noel, A. S. Seyffert, Shami Chatterjee, E. O. Angüner, David A. Green, Ramesh Karuppusamy, Zhiyuan Li, J. Devin, Dominik Elsaesser, F. Giordano, Santiago Ubach, Michael A. Nowak, Y. Kobayashi, F. Di Pierro, Iniyan Natarajan, A. Zech, M. Garczarczyk, Dmitriy Kostunin, Michael Janssen, Giacomo Bonnoli, Mariafelicia De Laurentis, Kuo Liu, G. Emery, Yutaro Kofuji, Antxon Alberdi, Marco Toliman Lucchini, R. A. Ong, Catherine Boisson, Daniel C. M. Palumbo, Stefan Klepser, Stefano Covino, Motoki Kino, Daniel Kerszberg, C. Armand, Maria Haupt, D. Zarić, K. Pfrang, R. López-Coto, M. Zacharias, Jae-Young Kim, Sheperd S. Doeleman, U. Barres de Almeida, Pratik Majumdar, M. V. Fonseca, Mosè Mariotti, G. Lamanna, Alexander Hahn, Sidika Merve Colak, R. J. Tuffs, B. Bi, Juan-Carlos Algaba, L. Oakes, D. Jankowsky, Y. Kajiwara, R. Marx, Bošnjak, John E. Barrett, Kotaro Niinuma, F. D'Ammando, Qingwen Wu, A. Yusafzai, Christian M. Fromm, Chi-kwan Chan, B. De Lotto, M. Kertzman, Manuela Mallamaci, H. Prokoph, Tadayuki Takahashi, Damir Lelas, Victor Doroshenko, E. Kasai, Lea Heckmann, Bong Won Sohn, Francesco Gabriele Saturni, Shiro Ikeda, T. Vuillaume, Laurent Loinard, G. Maurin, M. Füßling, Martin Will, Yi Chen, Gianluca Giavitto, Remo P. J. Tilanus, M. Spir-Jacob, Alessandro Montanari, Thomas Lohse, Tihomir Surić, J. van Scherpenberg, Per Friberg, He Sun, Luca Tosti, Kiyoaki Wajima, E. Ruiz-Velasco, Thomas Bylund, M. Balokovic, Feng Yuan, S. Nozaki, Mischa Breuhaus, Peter Galison, Y. A. Gallant, L. Olivera-Nieto, Dorota Sobczyńska, Maria-Isabel Bernardos, R. Rauth, Izumi Mizuno, Vincent L. Fish, S. G. Jorstad, Tomoki Saito, Giovanni Ceribella, Jacques Muller, J. P. Finley, Stefano Ansoldi, Boris Georgiev, Marcello Giroletti, Arturo I. Gómez-Ruiz, Karl M. Menten, Aristeidis Noutsos, P. deWilt, Junhan Kim, Alejandro Mus Mejías, Q. Remy, Dong-Jin Kim, P. G. Prada Moroni, Robert Wharton, Riccardo Paoletti, R. R. Prado, Zhi-Qiang Shen, S. Paiano, S. Chandra, Andrés Baquero, Anna Barnacka, Lucy Fortson, Wrijupan Bhattacharyya, Marc Ribó, E. de Ona Wilhelmi, Paul T. P. Ho, Yan-Rong Li, Derek Ward-Thompson, M. Scalici, G. Maneva, Constantin Steppa, Dimitrios Psaltis, A.M. Taylor, J. Damascene Mbarubucyeye, Daniel P. Marrone, Karl Mannheim, W. Boland, P. Morris, D. A. Prokhorov, M. Mohamed, Katsuaki Asano, Gernot Maier, Kotaro Moriyama, H. Odaka, M. Büchele, E. Pueschel, Kazuyoshi Nishijima, Christopher J. Duffy, H. M. Schutte, Camilla Maggio, Mark Kettenis, V. D'Elia, Saverio Lombardi, Ramprasad Rao, Ivica Puljak, R. Mirzoyan, V. Sahakian, Guang Yao Zhao, Adrian Biland, F. Werner, Rafal Moderski, Olivier Gentaz, Ullrich Schwanke, James M. Moran, S. Komossa, Yuzhu Cui, A. Jiménez-Rosales, Arash Roshanineshat, S. Ventura, Lindy Blackburn, David J. James, G. Hughes, Hidetoshi Kubo, Mansour Karami, José L. Gómez, P. Reichherzer, Davit Zargaryan, Paul Tiede, Koushik Chatterjee, Chunchong Ni, Roger Deane, Axel Donath, J. Rico, A. W. Chen, A. Fiasson, Jun Yi Koay, T. B. Humensky, Satoko Sawada-Satoh, Isak Delberth Davids, Alan P. Marscher, Alan E. E. Rogers, Rebecca Azulay, Kazuma Ishio, Paul M. Chesler, D. M. Strom, Carlo Vigorito, Marek Jamrozy, G. Pühlhofer, M. de Bony de Lavergne, Roberta Zanin, T. Schweizer, Elisa Prandini, Helene Sol, Rodolfo Carosi, M. Hörbe, T. Tavernier, Mareki Honma, M. Holler, Gordon T. Richards, Armelle Jardin-Blicq, Paolo Marchegiani, Sang-Sung Lee, D. Huber, Ashot Chilingarian, Nikola Godinovic, F. Ait Benkhali, Jason Dexter, Do-Young Byun, Anton Dmytriiev, Massimo Persic, Alicia Fattorini, L. Dirson, Cosimo Nigro, E. Roache, Sargis Gasparyan, S. Schwemmer, Sara Issaoun, Jessica Dempsey, Andrea Santangelo, Włodek Kluźniak, Mel Rose, Huib Jan van Langevelde, D. J. van der Walt, Elisabetta Liuzzo, A. Stamerra, John Hoang, Michelle Tsirou, Wolfgang Rhode, Tomohisa Kawashima, L. A. Antonelli, Carolin Wunderlich, Keiichi Asada, David A. Williams, Joachim Hahn, P. Moriarty, T. M. Crawford, P. Da Vela, L. Rinchiuso, E. Molina, F. Peter Schloerb, Lovro Pavletić, S. Steinmassl, Des Small, Christoph Deil, Stefano Menchiari, Dan Bintley, K. Nakashima, Alice Donini, David H. Hughes, Heinrich J. Völk, Mohanraj Senniappan, K. A. Farrell, M. Renaud, J. A. Barrio, Miriam Lucio Martinez, Rachel Simoni, P. T. O'Brien, E. Colombo, V. Barbosa Martins, M. Orienti, Efthalia Traianou, Lluis Font, B. Machado de Oliveira Fraga, Y. Suda, J. Neilsen, John Conway, Eduardo Ros, Gibwa Musoke, Tarek M. Hassan, J. Bolmont, A. Sinha, Halim Ashkar, M.-H. Grondin, Daniel Nieto, Lab Saha, Fabrizio Tavecchio, Hyunwook Ro, Michael H. Hecht, Markus Böttcher, Antonio Fuentes, Simone Mender, Moritz Hütten, Ue-Li Pen, Yosuke Mizuno, Gopal Narayanan, Lei Huang, H. Abdalla, M. A. Kastendieck, Nicola Marchili, I. Snidaric, S. Sánchez, G. Vasileiadis, Kari Nilsson, Alexander W. Raymond, Greg Lindahl, Gregory Desvignes, Sascha Trippe, Sanae Inoue, Giacomo D'Amico, W. Jin, B. van Soelen, Andrew Chael, Anne Kathrin Baczko, Shunsuke Sakurai, L. Giunti, A. Nayerhoda, Walter Alef, Jamie Holder, Stefano Truzzi, Pablo Peñil, M. J. Lang, Francois Brun, Frank M. Rieger, V. Vitale, George N. Wong, Jirong Mao, S. Caroff, J. Kushida, André Young, Ru-Sen Lu, Daniel Morcuende, Jose Luis Contreras, Kazuhiro Hada, Juan Cortina, C. van Eldik, Pablo Torne, Raymond Blundell, Jarred Gershon Green, C. B. Adams, James M. Cordes, Jonathan Weintroub, Q. Piel, A. Berti, James E. M. Watson, G. Peron, Ken Young, Garret Cotter, Dario Hrupec, Jonathan Mackey, K. Ragan, John E. Carlstrom, Michael Backes, Tim Holch, D. Hadasch, Stawarz, F. Niederwanger, Feryal Özel, Lia Medeiros, A. Weinstein, Mitsunari Takahashi, Manuel Delfino, C. Y. Kuo, Aviad Levis, Francesco Longo, K. Kosack, Konrad Bernlöhr, Jacco Vink, C. Moore, Michael Bremer, Jim Davies, Jadyn Anczarski, Patrick M. Koch, Sabrina Casanova, Ming-Tang Chen, B. Peyaud, Christian Stegmann, Stefan Wagner, C. Perennes, Yasunobu Uchiyama, David Kieda, Chet Ruszczyk, Hiroshi Nagai, M. Curyło, Andrei Lobanov, Ana Babić, E. Moulin, Tomasz Bulik, Britton Jeter, I. Vovk, Martin Makariev, C. van Rensburg, Oscar Blanch, Rocco Lico, Silke Britzen, Misao Sasaki, A. Reimer, V. Poireau, R. Adam, David Ball, Mark Reynolds, D. Miceli, John L. Quinn, Roberto Garcia, J. F. Glicenstein, D. Ribeiro, A. Wierzcholska, Geoffrey B. Crew, Bruno Khelifi, David Sánchez-Arguelles, Ilse van Bemmel, Michael D. Johnson, J. Anton Zensus, Dominik Baack, Manuel Meyer, E. V. Kravchenko, I. Jiménez, Thomas Bronzwaer, Reshmi Mukherjee, D. Berge, C. Giuri, Kleopas Shiningayamwe, Shan Shan Zhao, Yuki Iwamura, A. D. Falcone, Lenka Tomankova, Carsten Kramer, Jan Wagner, Christian Fruck, B. Rudak, Jordy Davelaar, V. Marandon, K. Katarzyński, Roberto Neri, The EHT MWL Science Working Group, Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Instituto de RadioAstronomía Milimétrica (IRAM), Laboratoire Leprince-Ringuet (LLR), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Centre de Physique des Particules de Marseille (CPPM), Aix Marseille Université (AMU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Annecy de Physique des Particules (LAPP), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire Univers et Théories (LUTH (UMR_8102)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE (UMR_7585)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire Univers et Particules de Montpellier (LUPM), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Groupe de Physique des Solides (GPS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL), Event Horizon Telescope, Fermi-LAT, H.E.S.S., MAGIC, VERITAS, EAVN, High Energy Astrophys. & Astropart. Phys (API, FNWI), API Other Research (FNWI), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Algaba, Jc, Anczarski, J, Asada, K, Balokovic, M, Chandra, S, Cui, Yz, Falcone, Ad, Giroletti, M, Goddi, C, Hada, K, Haggard, D, Jorstad, S, Kaur, A, Kawashima, T, Keating, G, Kim, Jy, Kino, M, Komossa, S, Kravchenko, Ev, Krichbaum, Tp, Lee, S, Lu, R, Lucchini, M, Markoff, S, Neilsen, J, Nowak, Ma, Park, J, Principe, G, Ramakrishnan, V, Reynolds, Mt, Sasada, M, Savchenko, S, Williamson, Ke, Longo, F, Et, Al., University of Michigan, Department of Electronics and Nanoengineering, Aalto-yliopisto, Aalto University, Algaba, J. C., Anczarski, J., Asada, K., Balokovic, M., Chandra, S., Cui, Y. -Z., Falcone, A. D., Giroletti, M., Goddi, C., Hada, K., Haggard, D., Jorstad, S., Kaur, A., Kawashima, T., Keating, G., Kim, J. -Y., Kino, M., Komossa, S., Kravchenko, E. V., Krichbaum, T. P., Lee, S. -S., Lu, R. -S., Lucchini, M., Markoff, S., Neilsen, J., Nowak, M. A., Park, J., Principe, G., Ramakrishnan, V., Reynolds, M. T., Sasada, M., Savchenko, S. S., Williamson, K. E., Akiyama, K., Alberdi, A., Alef, W., Anantua, R., Azulay, R., Baczko, A. -K., Ball, D., Barrett, J., Bintley, D., Benson, B. A., Blackburn, L., Blundell, R., Boland, W., Bouman, K. L., Bower, G. C., Boyce, H., Bremer, M., Brinkerink, C. D., Brissenden, R., Britzen, S., Broderick, A. E., Broguiere, D., Bronzwaer, T., Byun, D. -Y., Carlstrom, J. E., Chael, A., Chan, C. -K., Chatterjee, S., Chatterjee, K., Chen, M. -T., Chen, Y., Chesler, P. M., Cho, I., Christian, P., Conway, J. E., Cordes, J. M., Crawford, T. M., Crew, G. B., Cruz-Osorio, A., Davelaar, J., De Laurentis, M., Deane, R., Dempsey, J., Desvignes, G., Dexter, J., Doeleman, S. S., Eatough, R. P., Falcke, H., Farah, J., Fish, V. L., Fomalont, E., Ford, H. A., Fraga-Encinas, R., Friberg, P., Fromm, C. M., Fuentes, A., Galison, P., Gammie, C. F., Garcia, R., Gentaz, O., Georgiev, B., Gold, R., Gomez, J. L., Gomez-Ruiz, A. I., Gu, M., Gurwell, M., Hecht, M. H., Hesper, R., Ho, L. C., Ho, P., Honma, M., Huang, C. -W. L., Huang, L., Hughes, D. H., Ikeda, S., Inoue, M., Issaoun, S., James, D. J., Jannuzi, B. T., Janssen, M., Jeter, B., Jiang, W., Jimenez-Rosales, A., Johnson, M. D., Jung, T., Karami, M., Karuppusamy, R., Kettenis, M., Kim, D. -J., Kim, J., Koay, J. Y., Kofuji, Y., Koch, P. M., Koyama, S., Kramer, M., Kramer, C., Kuo, C. -Y., Lauer, T. R., Levis, A., Li, Y. -R., Li, Z., Lindqvist, M., Lico, R., Lindahl, G., Liu, J., Liu, K., Liuzzo, E., Lo, W. -P., Lobanov, A. P., Loinard, L., Lonsdale, C., Macdonald, N. R., Mao, J., Marchili, N., Marrone, D. P., Marscher, A. P., Marti-Vidal, I., Matsushita, S., Matthews, L. D., Medeiros, L., Menten, K. M., Mizuno, I., Mizuno, Y., Moran, J. M., Moriyama, K., Moscibrodzka, M., Muller, C., Musoke, G., Mejias, A. M., Nagai, H., Nagar, N. M., Nakamura, M., Narayan, R., Narayanan, G., Natarajan, I., Nathanail, A., Neri, R., Ni, C., Noutsos, A., Okino, H., Olivares, H., Ortiz-Leon, G. N., Oyama, T., Ozel, F., Palumbo, D. C. M., Patel, N., Pen, U. -L., Pesce, D. W., Pietu, V., Plambeck, R., Popstefanija, A., Porth, O., Potzl, F. M., Prather, B., Preciado-Lopez, J. A., Psaltis, D., Pu, H. -Y., Rao, R., Rawlings, M. G., Raymond, A. W., Rezzolla, L., Ricarte, A., Ripperda, B., Roelofs, F., Rogers, A., Ros, E., Rose, M., Roshanineshat, A., Rottmann, H., Roy, A. L., Ruszczyk, C., Rygl, K. L. J., Sanchez, S., Sanchez-Arguelles, D., Savolainen, T., Schloerb, F. P., Schuster, K. -F., Shao, L., Shen, Z., Small, D., Sohn, B. W., Soohoo, J., Sun, H., Tazaki, F., Tetarenko, A. J., Tiede, P., Tilanus, R. P. J., Titus, M., Toma, K., Torne, P., Trent, T., Traianou, E., Trippe, S., Van Bemmel, I., Van Langevelde, H. J., Van Rossum, D. R., Wagner, J., Ward-Thompson, D., Wardle, J., Weintroub, J., Wex, N., Wharton, R., Wielgus, M., Wong, G. N., Wu, Q., Yoon, D., Young, A., Young, K., Younsi, Z., Yuan, F., Yuan, Y. -F., Zensus, J. A., Zhao, G. -Y., Zhao, S. -S., D'Ammando, F., Orienti, M., Abdalla, H., Adam, R., Aharonian, F., Benkhali, F. A., Anguner, E. O., Arcaro, C., Armand, C., Armstrong, T., Ashkar, H., Backes, M., Baghmanyan, V., Barbosa Martins, V., Barnacka, A., Barnard, M., Becherini, Y., Berge, D., Bernlohr, K., Bi, B., Bottcher, M., Boisson, C., Bolmont, J., De Bony De Lavergne, M., Breuhaus, M., Brun, F., Brun, P., Bryan, M., Buchele, M., Bulik, T., Bylund, T., Caroff, S., Carosi, A., Casanova, S., Chand, T., Chen, A., Cotter, G., Curylo, M., Damascene Mbarubucyeye, J., Davids, I. D., Davies, J., Deil, C., Devin, J., Dewilt, P., Dirson, L., Djannati-Atai, A., Dmytriiev, A., Donath, A., Doroshenko, V., Duffy, C., Dyks, J., Egberts, K., Eichhorn, F., Einecke, S., Emery, G., Ernenwein, J. -P., Feijen, K., Fegan, S., Fiasson, A., De Clairfontaine, G. F., Fontaine, G., Funk, S., Fussling, M., Gabici, S., Gallant, Y. A., Giavitto, G., Giunti, L., Glawion, D., Glicenstein, J. F., Gottschall, D., Grondin, M. -H., Hahn, J., Haupt, M., Hermann, G., Hinton, J. A., Hofmann, W., Hoischen, C., Holch, T. L., Holler, M., Horbe, M., Horns, D., Huber, D., Jamrozy, M., Jankowsky, D., Jankowsky, F., Jardin-Blicq, A., Joshi, V., Jung-Richardt, I., Kasai, E., Kastendieck, M. A., Katarzynski, K., Katz, U., Khangulyan, D., Khelifi, B., Klepser, S., Kluzniak, W., Komin, N., Konno, R., Kosack, K., Kostunin, D., Kreter, M., Lamanna, G., Lemiere, A., Lemoine-Goumard, M., Lenain, J. -P., Levy, C., Lohse, T., Lypova, I., Mackey, J., Majumdar, J., Malyshev, D., Marandon, V., Marchegiani, P., Marcowith, A., Mares, A., Marti-Devesa, G., Marx, R., Maurin, G., Meintjes, P. J., Meyer, M., Moderski, R., Mohamed, M., Mohrmann, L., Montanari, A., Moore, C., Morris, P., Moulin, E., Muller, J., Murach, T., Nakashima, K., Nayerhoda, A., De Naurois, M., Ndiyavala, H., Niederwanger, F., Niemiec, J., Oakes, L., O'Brien, P., Odaka, H., Ohm, S., Olivera-Nieto, L., De Ona Wilhelmi, E., Ostrowski, M., Panter, M., Panny, S., Parsons, R. D., Peron, G., Peyaud, B., Piel, Q., Pita, S., Poireau, V., Noel, A. P., Prokhorov, D. A., Prokoph, H., Puhlhofer, G., Punch, M., Quirrenbach, A., Rauth, R., Reichherzer, P., Reimer, A., Reimer, O., Remy, Q., Renaud, M., Rieger, F., Rinchiuso, L., Romoli, C., Rowell, G., Rudak, B., Ruiz-Velasco, E., Sahakian, V., Sailer, S., Sanchez, D. A., Santangelo, A., Sasaki, M., Scalici, M., Schutte, H. M., Schwanke, U., Schwemmer, S., Seglar-Arroyo, M., Senniappan, M., Seyffert, A. S., Shafi, N., Shiningayamwe, K., Simoni, R., Sinha, A., Sol, H., Specovius, A., Spencer, S., Spir-Jacob, M., Stawarz, L., Sun, L., Steenkamp, R., Stegmann, C., Steinmassl, S., Steppa, C., Takahashi, T., Tavernier, T., Taylor, A. M., Terrier, R., Tiziani, D., Tluczykont, M., Tomankova, L., Trichard, C., Tsirou, M., Tuffs, R., Uchiyama, Y., Van Der Walt, D. J., Van Eldik, C., Van Rensburg, C., Van Soelen, B., Vasileiadis, G., Veh, J., Venter, C., Vincent, P., Vink, J., Volk, H. J., Vuillaume, T., Wadiasingh, Z., Wagner, S. J., Watson, J., Werner, F., White, R., Wierzcholska, A., Wong, Y. W., Yusafzai, A., Zacharias, M., Zanin, R., Zargaryan, D., Zdziarski, A. A., Zech, A., Zhu, S. J., Zorn, J., Zouari, S., Zywucka, N., Acciari, V. A., Ansoldi, S., Antonelli, L. A., Engels, A. A., Artero, M., Asano, K., Baack, D., Babic, A., Baquero, A., De Almeida, U. B., Barrio, J. A., Becerra Gonzalez, J., Bednarek, W., Bellizzi, L., Bernardini, E., Bernardos, M., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Bosnjak, Z., Busetto, G., Carosi, R., Ceribella, G., Cerruti, M., Chai, Y., Chilingarian, A., Cikota, S., Colak, S. M., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Amico, G., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Delgado Mendez, C., Depaoli, D., Di Pierro, F., Di Venere, L., Do Souto Espineira, E., Dominis Prester, D., Donini, A., Dorner, D., Doro, M., Elsaesser, D., Fallah Ramazani, V., Fattorini, A., Ferrara, G., Fonseca, M. V., Font, L., Fruck, C., Fukami, S., Garcia Lopez, R. J., Garczarczyk, M., Gasparyan, S., Gaug, M., Giglietto, N., Giordano, F., Gliwny, P., Godinovic, N., Green, J. G., Green, D., Hadasch, D., Hahn, A., Heckmann, L., Herrera, J., Hoang, J., Hrupec, D., Hutten, M., Inada, T., Inoue, S., Ishio, K., Iwamura, Y., Jimenez, I., Jormanainen, J., Jouvin, L., Kajiwara, Y., Karjalainen, M., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., Lopez-Coto, R., Lopez-Moya, M., Lopez-Oramas, A., Loporchio, S., Machado De Oliveira Fraga, B., Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martinez, M., Mazin, D., Menchiari, S., Mender, S., Micanovic, S., Miceli, D., Miener, T., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Neustroev, V., Nigro, C., Nilsson, K., Nishijima, K., Noda, K., Nozaki, S., Ohtani, Y., Oka, T., Otero-Santos, J., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Pavletic, L., Penil, P., Perennes, C., Persic, M., Moroni, P. G. P., Prandini, E., Priyadarshi, C., Puljak, I., Rhode, W., Ribo, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Saturni, F. G., Schleicher, B., Schmidt, K., Schweizer, T., Sitarek, J., Snidaric, I., Sobczynska, D., Spolon, A., Stamerra, A., Strom, D., Strzys, M., Suda, Y., Suric, T., Takahashi, M., Tavecchio, F., Temnikov, P., Terzic, T., Teshima, M., Tosti, L., Truzzi, S., Tutone, A., Ubach, S., Van Scherpenberg, J., Vanzo, G., Vazquez Acosta, M., Ventura, S., Verguilov, V., Vigorito, C. F., Vitale, V., Vovk, I., Will, M., Wunderlich, C., Zaric, D., Adams, C. B., Benbow, W., Brill, A., Capasso, M., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Errando, M., Farrell, K. A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gent, A., Giuri, C., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kieda, D., Kumar, S., Lang, M. J., Lundy, M., Maier, G., Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Patel, S., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Richards, G. T., Roache, E., Rulten, C., Ryan, J. L., Santander, M., Sembroski, G. H., Shang, R., Weinstein, A., Williams, D. A., Williamson, T. J., Hirota, T., Cui, L., Niinuma, K., Ro, H., Sakai, N., Sawada-Satoh, S., Wajima, K., Wang, N., Liu, X., Yonekura, Y., German Research Foundation, Istituto Nazionale di Fisica Nucleare, Swiss National Science Foundation, Ministerio de Ciencia, Innovación y Universidades (España), Department of Atomic Energy (India), University of Tokyo, Japan Society for the Promotion of Science, Ministry of Education and Scientific Research (Romania), Academy of Finland, La Caixa, Croatian Science Foundation, Generalitat de Catalunya, Polish National Agency for Academic Exchange, University of Rijeka, Department of Energy (US), Smithsonian Institution, Astronomy, and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2)
Subjects: Accretion, 010504 meteorology & atmospheric sciences, Astronomy, Flux, Astrophysics, 7. Clean energy, 01 natural sciences, Active galactic nuclei, Radio cores, Low-luminosity active galactic nuclei, High energy astrophysics, Astrophysical black holes, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, 010303 astronomy & astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, astro-ph.HE, Radio core, Accretion (meteorology), 520 Astronomie und zugeordnete Wissenschaften, Low-luminosity, active galactic nuclei, Astrophysical black hole, astro-ph.CO, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Active galactic nucleus, High-energy astronomy, astro-ph.GA, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, F500, Astrophysics::Cosmology and Extragalactic Astrophysics, High energy astrophysic, 0103 physical sciences, Very-long-baseline interferometry, ddc:530, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Event Horizon Telescope, Supermassive black hole, Astronomy and Astrophysics, 530 Physik, Galaxy, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ddc:520, HESS - Abteilung Hinton, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Full list of authors: EHT MWL Science Working Group; Algaba, J. C.; Anczarski, J.; Asada, K.; Baloković, M.; Chandra, S.; Cui, Y. -Z.; Falcone, A. D.; Giroletti, M.; Goddi, C.; Hada, K.; Haggard, D.; Jorstad, S.; Kaur, A.; Kawashima, T.; Keating, G.; Kim, J. -Y.; Kino, M.; Komossa, S.; Kravchenko, E. V.; Krichbaum, T. P.; Lee, S. -S.; Lu, R. -S.; Lucchini, M.; Markoff, S.; Neilsen, J.; Nowak, M. A.; Park, J.; Principe, G.; Ramakrishnan, V.; Reynolds, M. T.; Sasada, M.; Savchenko, S. S.; Williamson, K. E.; Event Horizon Telescope Collaboration; Akiyama, Kazunori; Alberdi, Antxon; Alef, Walter; Anantua, Richard; Azulay, Rebecca; Baczko, Anne-Kathrin; Ball, David; Barrett, John; Bintley, Dan; Benson, Bradford A.; Blackburn, Lindy; Blundell, Raymond; Boland, Wilfred; Bouman, Katherine L.; Bower, Geoffrey C.; Boyce, Hope; Bremer, Michael; Brinkerink, Christiaan D.; Brissenden, Roger; Britzen, Silke; Broderick, Avery E.; Broguiere, Dominique; Bronzwaer, Thomas; Byun, Do-Young; Carlstrom, John E.; Chael, Andrew; Chan, Chi-Kwan; Chatterjee, Shami; Chatterjee, Koushik; Chen, Ming-Tang; Chen, Yongjun; Chesler, Paul M.; Cho, Ilje; Christian, Pierre; Conway, John E.; Cordes, James M.; Crawford, Thomas M.; Crew, Geoffrey B.; Cruz-Osorio, Alejandro; Davelaar, Jordy; de Laurentis, Mariafelicia; Deane, Roger; Dempsey, Jessica; Desvignes, Gregory; Dexter, Jason; Doeleman, Sheperd S.; Eatough, Ralph P.; Falcke, Heino; Farah, Joseph; Fish, Vincent L.; Fomalont, Ed; Ford, H. Alyson; Fraga-Encinas, Raquel; Friberg, Per; Fromm, Christian M.; Fuentes, Antonio; Galison, Peter; Gammie, Charles F.; García, Roberto; Gentaz, Olivier; Georgiev, Boris; Gold, Roman; Gómez, José L.; Gómez-Ruiz, Arturo I.; Gu, Minfeng; Gurwell, Mark; Hecht, Michael H.; Hesper, Ronald; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih-Wei L.; Huang, Lei; Hughes, David H.; Ikeda, Shiro; Inoue, Makoto; Issaoun, Sara; James, David J.; Jannuzi, Buell T.; Janssen, Michael; Jeter, Britton; Jiang, Wu; Jiménez-Rosales, Alejandra; Johnson, Michael D.; Jung, Taehyun; Karami, Mansour; Karuppusamy, Ramesh; Kettenis, Mark; Kim, Dong-Jin; Kim, Jongsoo; Kim, Junhan; Koay, Jun Yi; Kofuji, Yutaro; Koch, Patrick M.; Koyama, Shoko; Kramer, Michael; Kramer, Carsten; Kuo, Cheng-Yu; Lauer, Tod R.; Levis, Aviad; Li, Yan-Rong; Li, Zhiyuan; Lindqvist, Michael; Lico, Rocco; Lindahl, Greg; Liu, Jun; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen-Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin; MacDonald, Nicholas R.; Mao, Jirong; Marchili, Nicola; Marrone, Daniel P.; Marscher, Alan P.; Martí-Vidal, Iván; Matsushita, Satoki; Matthews, Lynn D.; Medeiros, Lia; Menten, Karl M.; Mizuno, Izumi; Mizuno, Yosuke; Moran, James M.; Moriyama, Kotaro; Moscibrodzka, Monika; Müller, Cornelia; Musoke, Gibwa; Mejías, Alejandro Mus; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Narayan, Ramesh; Narayanan, Gopal; Natarajan, Iniyan; Nathanail, Antonios; Neri, Roberto; Ni, Chunchong; Noutsos, Aristeidis; Okino, Hiroki; Olivares, Héctor; Ortiz-León, Gisela N.; Oyama, Tomoaki; Özel, Feryal; Palumbo, Daniel C. M.; Patel, Nimesh; Pen, Ue-Li; Pesce, Dominic W.; Piétu, Vincent; Plambeck, Richard; Popstefanija, Aleksandar; Porth, Oliver; Pötzl, Felix M.; Prather, Ben; Preciado-López, Jorge A.; Psaltis, Dimitrios; Pu, Hung-Yi; Rao, Ramprasad; Rawlings, Mark G.; Raymond, Alexander W.; Rezzolla, Luciano; Ricarte, Angelo; Ripperda, Bart; Roelofs, Freek; Rogers, Alan; Ros, Eduardo; Rose, Mel; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruszczyk, Chet; Rygl, Kazi L. J.; Sánchez, Salvador; Sánchez-Arguelles, David; Savolainen, Tuomas; Schloerb, F. Peter; Schuster, Karl-Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; Soohoo, Jason; Sun, He; Tazaki, Fumie; Tetarenko, Alexandra J.; Tiede, Paul; Tilanus, Remo P. J.; Titus, Michael; Toma, Kenji; Torne, Pablo; Trent, Tyler; Traianou, Efthalia; Trippe, Sascha; van Bemmel, Ilse; van Langevelde, Huib Jan; van Rossum, Daniel R.; Wagner, Jan; Ward-Thompson, Derek; Wardle, John; Weintroub, Jonathan; Wex, Norbert; Wharton, Robert; Wielgus, Maciek; Wong, George N.; Wu, Qingwen; Yoon, Doosoo; Young, André; Young, Ken; Younsi, Ziri; Yuan, Feng; Yuan, Ye-Fei; Zensus, J. Anton; Zhao, Guang-Yao; Zhao, Shan-Shan; Fermi Large Area Telescope Collaboration; Principe, G.; Giroletti, M.; D'Ammando, F.; Orienti, M.; H. E. S. S. Collaboration; Abdalla, H.; Adam, R.; Aharonian, F.; Benkhali, F. Ait; Angüner, E. O.; Arcaro, C.; Armand, C.; Armstrong, T.; Ashkar, H.; Backes, M.; Baghmanyan, V.; Barbosa Martins, V.; Barnacka, A.; Barnard, M.; Becherini, Y.; Berge, D.; Bernlöhr, K.; Bi, B.; Böttcher, M.; Boisson, C.; Bolmont, J.; de Lavergne, M. De Bony; Breuhaus, M.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Bylund, T.; Caroff, S.; Carosi, A.; Casanova, S.; Chand, T.; Chen, A.; Cotter, G.; Curyło, M.; Damascene Mbarubucyeye, J.; Davids, I. D.; Davies, J.; Deil, C.; Devin, J.; Dewilt, P.; Dirson, L.; Djannati-Ataï, A.; Dmytriiev, A.; Donath, A.; Doroshenko, V.; Duffy, C.; Dyks, J.; Egberts, K.; Eichhorn, F.; Einecke, S.; Emery, G.; Ernenwein, J. -P.; Feijen, K.; Fegan, S.; Fiasson, A.; de Clairfontaine, G. Fichet; Fontaine, G.; Funk, S.; Füßling, M.; Gabici, S.; Gallant, Y. A.; Giavitto, G.; Giunti, L.; Glawion, D.; Glicenstein, J. F.; Gottschall, D.; Grondin, M. -H.; Hahn, J.; Haupt, M.; Hermann, G.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holch, T. L.; Holler, M.; Hörbe, M.; Horns, D.; Huber, D.; Jamrozy, M.; Jankowsky, D.; Jankowsky, F.; Jardin-Blicq, A.; Joshi, V.; Jung-Richardt, I.; Kasai, E.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Khangulyan, D.; Khélifi, B.; Klepser, S.; Kluźniak, W.; Komin, Nu.; Konno, R.; Kosack, K.; Kostunin, D.; Kreter, M.; Lamanna, G.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J. -P.; Levy, C.; Lohse, T.; Lypova, I.; Mackey, J.; Majumdar, J.; Malyshev, D.; Malyshev, D.; Marandon, V.; Marchegiani, P.; Marcowith, A.; Mares, A.; Martí-Devesa, G.; Marx, R.; Maurin, G.; Meintjes, P. J.; Meyer, M.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Montanari, A.; Moore, C.; Morris, P.; Moulin, E.; Muller, J.; Murach, T.; Nakashima, K.; Nayerhoda, A.; de Naurois, M.; Ndiyavala, H.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Ohm, S.; Olivera-Nieto, L.; de Ona Wilhelmi, E.; Ostrowski, M.; Panter, M.; Panny, S.; Parsons, R. D.; Peron, G.; Peyaud, B.; Piel, Q.; Pita, S.; Poireau, V.; Noel, A. Priyana; Prokhorov, D. A.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Rauth, R.; Reichherzer, P.; Reimer, A.; Reimer, O.; Remy, Q.; Renaud, M.; Rieger, F.; Rinchiuso, L.; Romoli, C.; Rowell, G.; Rudak, B.; Ruiz-Velasco, E.; Sahakian, V.; Sailer, S.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Scalici, M.; Schutte, H. M.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Senniappan, M.; Seyffert, A. S.; Shafi, N.; Shiningayamwe, K.; Simoni, R.; Sinha, A.; Sol, H.; Specovius, A.; Spencer, S.; Spir-Jacob, M.; Stawarz, Ł.; Sun, L.; Steenkamp, R.; Stegmann, C.; Steinmassl, S.; Steppa, C.; Takahashi, T.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tiziani, D.; Tluczykont, M.; Tomankova, L.; Trichard, C.; Tsirou, M.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Vincent, P.; Vink, J.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Watson, J.; Werner, F.; White, R.; Wierzcholska, A.; Wong, Yu Wun; Yusafzai, A.; Zacharias, M.; Zanin, R.; Zargaryan, D.; Zdziarski, A. A.; Zech, A.; Zhu, S. J.; Zorn, J.; Zouari, S.; Żywucka, N.; MAGIC Collaboration; Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Engels, A. Arbet; Artero, M.; Asano, K.; Baack, D.; Babić, A.; Baquero, A.; de Almeida, U. Barres; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bellizzi, L.; Bernardini, E.; Bernardos, M.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch, O.; Bonnoli, G.; Bošnjak, Ž.; Busetto, G.; Carosi, R.; Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingarian, A.; Cikota, S.; Colak, S. M.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Amico, G.; D'Elia, V.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.; Delfino, M.; Delgado, J.; Delgado Mendez, C.; Depaoli, D.; di Pierro, F.; di Venere, L.; Do Souto Espiñeira, E.; Dominis Prester, D.; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Ramazani, V. Fallah; Fattorini, A.; Ferrara, G.; Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.; García López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović, N.; Green, J. G.; Green, D.; Hadasch, D.; Hahn, A.; Heckmann, L.; Herrera, J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada, T.; Inoue, S.; Ishio, K.; Iwamura, Y.; Jiménez, I.; Jormanainen, J.; Jouvin, L.; Kajiwara, Y.; Karjalainen, M.; Kerszberg, D.; Kobayashi, Y.; Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.; Lombardi, S.; Longo, F.; López-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio, S.; Machado de Oliveira Fraga, B.; Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menchiari, S.; Mender, S.; Mićanović, S.; Miceli, D.; Miener, T.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti, E.; Neustroev, V.; Nigro, C.; Nilsson, K.; Nishijima, K.; Noda, K.; Nozaki, S.; Ohtani, Y.; Oka, T.; Otero-Santos, J.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Pavletić, L.; Peñil, P.; Perennes, C.; Persic, M.; Moroni, P. G. Prada; Prandini, E.; Priyadarshi, C.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.; Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.; Saturni, F. G.; Schleicher, B.; Schmidt, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Spolon, A.; Stamerra, A.; Strom, D.; Strzys, M.; Suda, Y.; Surić, T.; Takahashi, M.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima, M.; Tosti, L.; Truzzi, S.; Tutone, A.; Ubach, S.; van Scherpenberg, J.; Vanzo, G.; Vazquez Acosta, M.; Ventura, S.; Verguilov, V.; Vigorito, C. F.; Vitale, V.; Vovk, I.; Will, M.; Wunderlich, C.; Zarić, D.; VERITAS Collaboration; Adams, C. B.; Benbow, W.; Brill, A.; Capasso, M.; Christiansen, J. L.; Chromey, A. J.; Daniel, M. K.; Errando, M.; Farrell, K. A.; Feng, Q.; Finley, J. P.; Fortson, L.; Furniss, A.; Gent, A.; Giuri, C.; Hassan, T.; Hervet, O.; Holder, J.; Hughes, G.; Humensky, T. B.; Jin, W.; Kaaret, P.; Kertzman, M.; Kieda, D.; Kumar, S.; Lang, M. J.; Lundy, M.; Maier, G.; Moriarty, P.; Mukherjee, R.; Nieto, D.; Nievas-Rosillo, M.; O'Brien, S.; Ong, R. A.; Otte, A. N.; Patel, S.; Pfrang, K.; Pohl, M.; Prado, R. R.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Ribeiro, D.; Richards, G. T.; Roache, E.; Rulten, C.; Ryan, J. L.; Santander, M.; Sembroski, G. H.; Shang, R.; Weinstein, A.; Williams, D. A.; Williamson, T. J.; Eavn Collaboration; Hirota, Tomoya; Cui, Lang; Niinuma, Kotaro; Ro, Hyunwook; Sakai, Nobuyuki; Sawada-Satoh, Satoko; Wajima, Kiyoaki; Wang, Na; Liu, Xiang; Yonekura, Yoshinori, In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass ∼6.5 × 109 M o˙. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous γ-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the γ-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded., The financial support of the German BMBF, MPG and HGF; the Italian INFN and INAF; the Swiss National Fund SNF; the ERDF under the Spanish Ministerio de Ciencia e Innovacion (MICINN) (FPA2017-87859-P, FPA2017-85668-P, FPA2017- 82729-C6-5-R, FPA2017-90566-REDC, PID2019-104114RBC31, PID2019-104114RB-C32, PID2019-105510GB-C31,PID 2019-107847RB-C41, PID2019-107847RB-C42, PID2019- 107988GB-C22); the Indian Department of Atomic Energy; the Japanese ICRR, the University of Tokyo, JSPS, and MEXT; the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-268/16.12.2019 and the Academy of Finland grant No. 320045 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia “Severo Ochoa” SEV-2016-0588 and CEX2019- 000920-S, and “Maria de Maeztu” CEX2019-000918-M, the Unidad de Excelencia “Maria de Maeztu” MDM-2015-0509- 18-2 and the “la Caixa” Foundation (fellowship LCF/BQ/ PI18/11630012) and by the CERCA program of the Generalitat de Catalunya; by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project 13.12.1.3.02; by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3; the Polish National Research Centre grant UMO-2016/22/M/ST9/00382; and by the Brazilian MCTIC, CNPq, and FAPERJ. This research is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation and the Smithsonian Institution, by NSERC in Canada, and by the Helmholtz Association in Germany. This research used resources provided by the Open Science Grid, which is supported by the National Science Foundation and the U.S. Department of Energy’s Office of Science, and resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231. We acknowledge the excellent work of the technical support staff at the Fred Lawrence Whipple Observatory and at the collaborating institutions in the construction and operation of the instrument.
Published: 2021
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17. Alignment of the optical system of the 9.7-m prototype Schwarzchild-Coulder Telescope

Author: Alasdair E. Gent, E. Fiandrini, Arturo Iriarte, Thomas Meures, Olivier Hervet, R. Shang, M. Valentino, Reshmi Mukherjee, K. L. Byrum, Corbin Covault, Nicola Giglietto, S. J. Fegan, G. Hughes, G. H. Tovmassian, A. Petrashyk, Akira Okumura, Wystan Benbow, C. Bonavolontà, G. Pareschi, J. Ruíz-Díaz-Soto, Daniel Nieto, B. Kim, G. Sironi, David Kieda, A. Brill, Ruben Alfaro, M. Caprai, Vladimir Vassiliev, N. La Palombara, Bruna Bertucci, S. Schlenstedt, Carla Aramo, Francesco Giordano, L. P. Taylor, M. J. Martínez González, J. H. Buckley, Elisabetta Bissaldi, R. A. Cameron, A. Boiano, R. Halliday, Q. Feng, Amy Furniss, Richard Bose, Julien Rousselle, B. A. W. Mode, T. B. Humensky, W. Jin, D. Ribeiro, Justin Vandenbroucke, Maria Ionica, P. Wilcox, M. Ambrosio, L. Stiaccini, M. Capasso, S. P. Wakely, P. Kaaret, E. Roache, Valerio Vagelli, Fernando Garfias, F. R. Pantaleo, Andrea Rugliancich, Michele Limon, Marcos Santander, S. Loporchio, L. Di Venere, N. Otte, J. Powell, G. Ambrosi, Luca Tosti, B. Stevenson, M. Bitossi, C. Adams, M. Garczarczyk, Peter Y. Yu, R. Paoletti, Salvo Scuderi, David A. Williams, ITA, USA, FRA, DEU, ESP, JPN, and MEX
Subjects: Pixel, business.industry, Computer science, Astrophysics::High Energy Astrophysical Phenomena, media_common.quotation_subject, Astrophysics::Instrumentation and Methods for Astrophysics, Field of view, Gamma-ray astronomy, Cherenkov Telescope Array, law.invention, Telescope, Optics, Crab Nebula, Observatory, Sky, law, Astrophysics::Solar and Stellar Astrophysics, business, media_common
Abstract: The novel 9.7m Schwarzschild-Couder Telescope (SCT), utilizing aspheric dual-mirror optical system, has been constructed as a prototype medium size x-ray telescope for the Cherenkov Telescope Array (CTA) observatory. The prototype SCT (pSCT) is designed to achieve simultaneously the wide (>= 8°) field of view and the superior imaging resolution (0.067 per pixel) to significantly improve scientific capabilities of the observatory in conducting the sky surveys, the follow-up observations of multi-messenger transients with poorly known initial localization and the morphology studies of x-ray sources with angular extent. In this submission, we describe the hardware and software implementations of the telescope optical system as well as the methods specifically developed to align its complex optical system, in which both primary and secondary mirrors are segmented. The pSCT has detected Crab Nebula in June 2020 during ongoing commissioning, which was delayed due to worldwide pandemic and is not yet completed. Verification of pSCT performance is continuing and further improvement of optical alignment is anticipated.
Published: 2020
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18. Demonstration of stellar intensity interferometry with the four VERITAS telescopes

Author: T. T.Y. Lin, K. Ragan, J. H. Buckley, A. Brill, Gernot Maier, S. P. Wakely, D. S. Hanna, Q. Feng, Nolan Matthews, A. J. Chromey, A. Weinstein, Lucy Fortson, R. A. Ong, Jonathan Davis, F. Krennrich, Tugdual LeBohec, T. J. Williamson, Anushka Udara Abeysekara, Olivier Hervet, Orel Gueta, P. Wilcox, S. O'Brien, S. Kumar, M. Lundy, J. P. Finley, Amy Furniss, M. K. Daniel, Reshmi Mukherjee, Gordon T. Richards, T. B. Humensky, C. Giuri, E. Pueschel, Martin Pohl, G. H. Sembroski, P. Kaaret, A. D. Falcone, P. Moriarty, M. Nievas-Rosillo, Jodi Christiansen, David Kieda, A. N. Otte, K. Pfrang, M. Kertzman, Jamie Holder, Marcos Santander, P. T. Reynolds, Alasdair E. Gent, R. R. Prado, David A. Williams, Wystan Benbow, G. Hughes, E. Roache, Tarek M. Hassan, John L. Quinn, D. Ribeiro, and James Ryan
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, law.invention, Telescope, Angular diameter, law, 0103 physical sciences, Astronomical interferometer, Astrophysics::Solar and Stellar Astrophysics, Angular resolution, 010306 general physics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Cherenkov radiation, Astrophysics::Galaxy Astrophysics, Physics, Stellar atmosphere, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astronomy and Astrophysics, Cherenkov Telescope Array, Interferometry, Astrophysics - Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: High angular resolution observations at optical wavelengths provide valuable insights in stellar astrophysics, directly measuring fundamental stellar parameters, and probing stellar atmospheres, circumstellar disks, elongation of rapidly rotating stars, and pulsations of Cepheid variable stars. The angular size of most stars are of order one milli-arcsecond or less, and to spatially resolve stellar disks and features at this scale requires an optical interferometer using an array of telescopes with baselines on the order of hundreds of meters. We report on the successful implementation of a stellar intensity interferometry system developed for the four VERITAS imaging atmospheric-Cherenkov telescopes. The system was used to measure the angular diameter of the two sub-mas stars $\beta$ Canis Majoris and $\epsilon$ Orionis with a precision better than 5%. The system utilizes an off-line approach where starlight intensity fluctuations recorded at each telescope are correlated post-observation. The technique can be readily scaled onto tens to hundreds of telescopes, providing a capability that has proven technically challenging to current generation optical amplitude interferometry observatories. This work demonstrates the feasibility of performing astrophysical measurements with imaging atmospheric-Cherenkov telescope arrays as intensity interferometers and the promise for integrating an intensity interferometry system within future observatories such as the Cherenkov Telescope Array., Comment: Accepted for publication in Nature Astronomy (2020)
Published: 2020

19. Probing the Properties of the Pulsar Wind in the Gamma-Ray Binary HESS J0632+057 with NuSTAR and VERITAS Observations

Author: P. Kaaret, R. Mukherjee, M. Nievas-Rosillo, N. Kelley-Hoskins, C. Giuri, Gernot Maier, E. Roache, Ralph Bird, David Kieda, R. A. Ong, Kaya Mori, K. Ragan, D. S. Hanna, Orel Gueta, Abraham D. Falcone, A. Brill, P. Wilcox, C. J. Hailey, Tarek M. Hassan, M. Kertzman, David A. Williams, A. N. Otte, Amy Furniss, G. H. Sembroski, A. Weinstein, Marcos Santander, A. J. Chromey, I. Sadeh, Robert Brose, Maria Krause, N. H. Park, I. Sushch, Wystan Benbow, J. P. Finley, T. J. Williamson, Jodi Christiansen, O. Hervet, A. Archer, A. Petrashyk, Jamie Holder, P. T. Reynolds, E. Pueschel, M. J. Lang, S. O'Brien, A. Gent, G. H. Gillanders, Q. Feng, Lucy Fortson, Shifra Mandel, D. Ribeiro, Gordon T. Richards, John L. Quinn, A. Wilhelm, Weiguang Cui, K. Pfrang, Daniel Nieto, G. Hughes, Martin Pohl, T. B. Humensky, S. Schlenstedt, P. Moriarty, M. Buchovecky, and R.R. Prado
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Spectral index, 010504 meteorology & atmospheric sciences, Be star, Astrophysics::High Energy Astrophysical Phenomena, Gamma ray, FOS: Physical sciences, Spectral density, Astronomy and Astrophysics, Electron, Astrophysics, Compact star, Light curve, 01 natural sciences, Pulsar, 13. Climate action, Space and Planetary Science, 0103 physical sciences, ddc:520, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract: HESS J0632+057 is a gamma-ray binary composed of a compact object orbiting a Be star with a period of about $315$ days. Extensive X-ray and TeV gamma-ray observations have revealed a peculiar light curve containing two peaks, separated by a dip. We present the results of simultaneous observations in hard X-rays with NuSTAR and in TeV gamma-rays with VERITAS, performed in November and December 2017. These observations correspond to the orbital phases $\phi\approx0.22$ and $0.3$, where the fluxes are rising towards the first light-curve peak. A significant variation of the spectral index from 1.77$\pm$0.05 to 1.56$\pm$0.05 is observed in the X-ray data. The multi-wavelength spectral energy distributions (SED) derived from the observations are interpreted in terms of a leptonic model, in which the compact object is assumed to be a pulsar and non-thermal radiation is emitted by high-energy electrons accelerated at the shock formed by the collision between the stellar and pulsar wind. The results of the SED fitting show that our data can be consistently described within this scenario, and allow us to estimate the magnetization of the pulsar wind at the location of the shock formation. The constraints on the pulsar-wind magnetization provided by our results are shown to be consistent with those obtained from other systems., Comment: Accepted for publication in The Astrophysical Journal
Published: 2020
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20. VERITAS Discovery of VHE Emission from the Radio Galaxy 3C 264: A Multi-Wavelength Study

Author: A. Brill, Alasdair E. Gent, James Ryan, Manel Errando, E. T. Meyer, Gordon T. Richards, Olivier Hervet, M. Kertzman, E. Roache, A. Archer, T. T.Y. Lin, K. Ragan, R. A. Ong, S. O'Brien, B. Stevenson, D. S. Hanna, G. Hughes, Wystan Benbow, P. Moriarty, Matthew L. Lister, C. B. Rulten, M. Lundy, K. Ramirez, Karlen Shahinyan, T. J. Williamson, Tarek M. Hassan, A. Wilhelm, David Kieda, Daniel Nieto, M. Nievas-Rosillo, A. C. Sadun, Jodi Christiansen, Jamie Holder, Marcos Santander, P. T. Reynolds, K. Pfrang, John L. Quinn, D. Ribeiro, R. Shang, M. J. Lang, Gernot Maier, A. D. Falcone, A. Weinstein, M. Pohl, S. P. Wakely, R. R. Prado, M. K. Daniel, P. Fortin, Ralph Bird, David A. Williams, Orel Gueta, P. Wilcox, J. H. Buckley, S. S. Scott, A. J. Chromey, Michael T. Carini, F. Krennrich, M. Georganopoulos, Reshmi Mukherjee, C. Giuri, Q. Feng, G. H. Gillanders, T. B. Humensky, P. Kaaret, Lucy Fortson, M. Buchovecky, G. H. Sembroski, E. Pueschel, Vladimir Vassiliev, and Amy Furniss
Subjects: 010504 meteorology & atmospheric sciences, Radio galaxy, atmosphere [Cherenkov counter], Astrophysics, cosmic background radiation, power spectrum, 01 natural sciences, law.invention, Astrophysical jet, law, pixel, ultraviolet, black hole, optical, dimension: 2, 010303 astronomy & astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), photon, 2 [dimension], Elliptical galaxy, Spectral energy distribution, VERITAS, Astrophysics - High Energy Astrophysical Phenomena, Lorentz, Active galactic nucleus, Astrophysics::High Energy Astrophysical Phenomena, radio wave [galaxy], energy spectrum, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Cherenkov counter: atmosphere, VHE, GLAST, Telescope, X-ray, 0103 physical sciences, structure, Very Long Baseline Array, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, polarization, synchrotron radiation, background, galaxy: radio wave, Astronomy and Astrophysics, Doppler effect, flux, Crab Nebula, Space and Planetary Science, gamma ray, ddc:520, spectral, statistical
Abstract: The astrophysical journal 896(1), 41 - (2020). doi:10.3847/1538-4357/ab910e, The radio source 3C 264, hosted by the giant elliptical galaxy NGC 3862, was observed with VERITAS between February 2017 and May 2019. These deep observations resulted in the discovery of very-high-energy (VHE; E $>100$ GeV) $\gamma$-ray emission from this active galaxy. An analysis of $\sim$57 hours of quality-selected live time yields a detection at the position of the source, corresponding to a statistical significance of 7.8 standard deviations above background. The observed VHE flux is variable on monthly time scales, with an elevated flux seen in 2018 observations. The VHE emission during this elevated state is well-characterized by a power-law spectrum with a photon index $\Gamma = 2.20 \pm 0.27$ and flux F($>315$ GeV) = ($7.6\pm 1.2_{\mathrm stat} \pm 2.3_{\mathrm syst})\times 10^{-13}$ cm$^{-2}$ s$^{-1}$, or approximately 0.7% of the Crab Nebula flux above the same threshold. 3C 264 ($z = 0.0217$) is the most distant radio galaxy detected at VHE, and the elevated state is thought to be similar to that of the famously outbursting jet in M 87. Consequently, extensive contemporaneous multi-wavelength data were acquired in 2018 at the time of the VHE high state. An analysis of these data, including VLBA, VLA, HST, Chandra and Swift observations in addition to the VERITAS data, is presented, along with a discussion of the resulting spectral energy distribution., Published by Univ.8743, Chicago, Ill. [u.a.]
Published: 2020
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21. An Archival Search for Neutron-star Mergers in Gravitational Waves and Very-high-energy Gamma Rays

Author: M. Lundy, Lucy Fortson, Reshmi Mukherjee, M. K. Daniel, A. Weinstein, C. Giuri, P. Kaaret, David Kieda, Olivier Hervet, C. E. McGrath, S. Márka, Wystan Benbow, Martin Pohl, A. D. Falcone, Alasdair E. Gent, P. Moriarty, R. A. Ong, James Ryan, S. Kumar, J. H. Buckley, R. R. Prado, P. T. Reynolds, M. Kertzman, Amy Furniss, M. Nievas-Rosillo, Nahee Park, A. J. Chromey, Doğa Veske, G. H. Sembroski, M. Capasso, Q. Feng, E. Pueschel, Imre Bartos, Jodi Christiansen, A. Brill, Daniel Nieto, David A. Williams, Marcos Santander, A. N. Otte, K. Pfrang, C. B. Adams, D. S. Hanna, G. Hughes, J. P. Finley, Jamie Holder, K. R. Corley, K. Ragan, R. Shang, T. J. Williamson, Z. Márka, S. O'Brien, E. Roache, K. A. Farrell, Tarek M. Hassan, John L. Quinn, D. Ribeiro, W. Jin, M. J. Lang, Manel Errando, S. Patel, T. B. Humensky, and Gernot Maier
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Gravitational wave, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, IACT, Gamma-ray astronomy, Cherenkov Telescope Array, 030226 pharmacology & pharmacy, 01 natural sciences, LIGO, 03 medical and health sciences, Neutron star, 0302 clinical medicine, Space and Planetary Science, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, Gamma-ray burst, 010303 astronomy & astrophysics, Cherenkov radiation
Abstract: The recent discovery of electromagnetic signals in coincidence with neutron-star mergers has solidified the importance of multimessenger campaigns in studying the most energetic astrophysical events. Pioneering multimessenger observatories, such as LIGO/Virgo and IceCube, record many candidate signals below the detection significance threshold. These sub-threshold event candidates are promising targets for multimessenger studies, as the information provided by them may, when combined with contemporaneous gamma-ray observations, lead to significant detections. Here we describe a new method that uses such candidates to search for transient events using archival very-high-energy gamma-ray data from imaging atmospheric Cherenkov telescopes (IACTs). We demonstrate the application of this method to sub-threshold binary neutron star (BNS) merger candidates identified in Advanced LIGO's first observing run. We identify eight hours of archival VERITAS observations coincident with seven BNS merger candidates and search them for TeV emission. No gamma-ray emission is detected; we calculate upper limits on the integral flux and compare them to a short gamma-ray burst model. We anticipate this search method to serve as a starting point for IACT searches with future LIGO/Virgo data releases as well as in other sub-threshold studies for multimessenger transients, such as IceCube neutrinos. Furthermore, it can be deployed immediately with other current-generation IACTs, and has the potential for real-time use that places minimal burden on experimental operations. Lastly, this method may serve as a pilot for studies with the Cherenkov Telescope Array, which has the potential to observe even larger fields of view in its divergent pointing mode.
Published: 2021
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22. A Search for Pulsed Very High-energy Gamma-Rays from 13 Young Pulsars in Archival VERITAS Data

Author: M. Buchovecky, S. O'Brien, A. Archer, Olivier Hervet, Wystan Benbow, Gordon T. Richards, E. Roache, Q. Feng, M. Pohl, Karlen Shahinyan, R. M. Wells, Tarek M. Hassan, A. Weinstein, T. B. Humensky, B. Zitzer, S. P. Wakely, Wei Cui, T. J. Williamson, I. Sushch, John L. Quinn, Alasdair E. Gent, P. Kaaret, D. S. Hanna, M. Kertzman, R. A. Ong, C. A. Johnson, K. Ragan, Ralph Bird, David Kieda, A. Wilhelm, Robert Brose, Lucy Fortson, J. P. Finley, Reshmi Mukherjee, M. J. Lang, Dirk Pandel, N. H. Park, A. Petrashyk, Orel Gueta, P. Moriarty, A. D. Falcone, G. H. Sembroski, N. Kelley-Hoskins, G. Hughes, P. Kar, Marcos Santander, A. N. Otte, Jamie Holder, P. Wilcox, I. Sadeh, David A. Williams, S. S. Scott, E. Pueschel, A. McCann, S. Kumar, J. Tyler, J. H. Buckley, A. J. Chromey, F. Krennrich, T. T.Y. Lin, and Amy Furniss
Subjects: Physics, High energy, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Gamma ray, Astrophysics::Instrumentation and Methods for Astrophysics, Institut für Physik und Astronomie, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Pulsar, Space and Planetary Science, 0103 physical sciences, ddc:520, ddc:530, 010303 astronomy & astrophysics
Abstract: The astrophysical journal / 1 876(2), 95 (2019). doi:10.3847/1538-4357/ab14f4, We conduct a search for periodic emission in the very high-energy (VHE) gamma-ray band (E > 100 GeV) from a total of 13 pulsars in an archival VERITAS data set with a total exposure of over 450 hr. The set of pulsars includes many of the brightest young gamma-ray pulsars visible in the Northern Hemisphere. The data analysis resulted in nondetections of pulsed VHE gamma-rays from each pulsar. Upper limits on a potential VHE gamma-ray flux are derived at the 95% confidence level above three energy thresholds using two methods. These are the first such searches for pulsed VHE emission from each of the pulsars, and the obtained limits constrain a possible flux component manifesting at VHEs as is seen for the Crab pulsar., Published by Institute of Physics Publ., London
Published: 2019
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23. Combined Dark Matter searches towards dwarf spheroidal galaxies with Fermi-LAT, HAWC, HESS, MAGIC and VERITAS

Author: Dirk Lennarz, Luis Villaseñor, Gernot Maier, Anne Lemiere, Daniel Rosa-Gonzalez, Samuel Timothy Spencer, Wystan Benbow, Victor Barbosa Martins, Raul Prado, Arache Djannati-Ataï, Regis Terrier, Dan Parsons, Francisco Salesa Greus, Dmitriy Kostunin, Joshua Wood, Carlo Romoli, César Alvarez, Carlo van Rensburg, Massimo Capasso, Sajan Kumar, P. Reichherzer, Anton Dmytriiev, Stefan Ohm, Chiara Giuri, Brian van Soelen, G. Peron, Christian Stegmann, Emma Ona-Wilhelmi, S. J. Fegan, Alison Peisker, Hawc, Garret Cotter, Gary Gillanders, Zhiqiu Huang, Krzysztof Katarzynski, Filiberto Hueyotl-Zahuantitla, Ian Herzog, D. A. Prokhorov, K. Kosack, Halim Ashkar, Fabian Leuschner, Manami Sasaki, Michael Schneider, Joe Lundeen, Markus Boettcher, Brian Humensky, Isak Delberth Davids, A. Fiasson, Stefan Wagner, Andreas Zech, Yasunobu Uchiyama, David Kieda, Michael DuVernois, Albert Seyffert, Gianluca Giavitto, Qi Feng, Andreas Specovius, Andrew James Smith, Catherine Boisson, L. Mohrmann, Roberta Zanin, Marek Jamrozy, Tomás Capistrán Rojas, K. Nakashima, Jamie Holder, Hao Zhou, Thomas Lohse, Mireia Nievas-Rosillo, Samuel Zouari, Ira Jung, Sebastian Panny, K. Bernloehr, Deivid Ribeiro, Andrea Santangelo, Kristi Engel, Josefa Becerra Gonzalez, Thomas Tavernier, Ke Fang, Rishi Babu, Yu Wun Wong, Gerd J. Kunde, Jean-Pierre Ernenwein, Henrike Fleischhack, P. T. O'Brien, Clemens Hoischen, A. A. Zdziarski, Kelly Malone, Helene Sol, Markus Holler, Manel Errando, Atreyee Sinha, Francois Brun, Heinrich J. Völk, Sumari Hattingh, Kirsten Tollefson, Johann van der Walt, Q. Remy, Felix Jankowsky, Samridha Kunwar, Johannes Veh, M. Fuessling, P. Vincent, Harm Schoorlemmer, Stefano Gabici, Miguel Mostafa, Tyler Williamson, Jacek Niemiec, Michal Ostrowski, J.-P. Lenain, Israel Martinez Castellanos, Felix Aharonian, Tadayuki Takahashi, Gerd Puehlhofer, Lei Sun, Jesús Martínez-Castro, Pooja Surajbali, Andrés Sandoval, Hugh Spackman, Takaaki Tanaka, Segev BenZvi, Alexandre Marcowith, Felix Werner, Olaf Reimer, Vincent Marandon, Alberto Carramiñana, S. Steinmassl, Mary Kertzman, Hannes Thiersen, Victor Doroshenko, Michael Backes, Hannah Jhee, G. Lamanna, Marcos Santander, Angel Noel, W. Jin, Gus Sinnis, B. Rudak, Alasdair E. Gent, Kathrin Egberts, Jonathan Mackey, Fernando Ureña-Mena, Paolo Marchegiani, Sonal Ramesh Patel, Laenita Lorraine Oberholzer, Tim Holch, Sami Caroff, Heiko Salzmann, E. Kasai, Alison Mitchell, Gregory Foote, Nukri Komin, Tom Armstrong, Michelle Hui, Ruo-Yu Shang, Binita Hona, Raquel Diaz Hernandez, Vardan Baghmanyan, Celine Armand, Alejandro Lara, David Berley, Hector Rueda Ricarte, Nissim Illich Fraija, Naomi Tsuji, Gaurang Yodh, Stefan Funk, Alicja Wierzcholska, Conor McGrath, Gerard Fontaine, C. Moore, Vikas Joshi, Dorit Glawion, T. Chand, M. U. Nisa, M.-H. Grondin, Arnaud Mares, David Sanchez, Ernesto Belmont-Moreno, Thomas Murach, Eucario Gonzalo Pérez Pérez, Paul Reynolds, Ignacio Taboada, Xiaojie Wang, Lucy Fortson, Martin Tluczykont, Thomas Brian Humensky, Juan de Dios Álvarez Romero, Robert Ellsworth, Hester Schutte, Justine Devin, Constantin Steppa, Richard White, Rachel Simoni, Karen S. Caballero Mora, Elisa Pueschel, Jason Fan, Tomasz Bulik, Lukas Nellen, Malgorzata Curlo, Lente Dreyer, J. Patrick Harding, Gilles Maurin, Humberto Martínez Huerta, Riaan Steenkamp, Arnulfo Zepeda, Johannes Schaefer, Werner Hofmann, Jim Hinton, Michael Punch, S. Sailer, Dmitry Khangulyan, Sergio Hernández Cadena, Charles Thorpe-Morgan, M. Hörbe, Stephan O'Brien, Ramin Marx, John L. Quinn, J. F. Glicenstein, V. Sahakian, M. Panter, Mora Durocher, U. Katz, Jacco Vink, Umberto Cotti, Tobias Kleiner, Petra Hüntemeyer, David Huber, Ullrich Schwanke, Diego Garcia Aguilar, Vladimir Vassiliev, Oscar Martinez, J. Bolmont, Cederik León de León, Brian Fick, Laura Olivera-Nieto, A. Yusafzai, David Hanna, James Buckley, Lorenzo Diaz, Yves Gallant, Guillermo García-Torales, Arun Babu Kollamparambil, James Ryan, Kayla Farrell, Sabrina Casanova, Bruno Khelifi, María Catalina Espinoza Hernández, Jorge Antonio Morales Soto, Mateo Fernandez Alonso, Matthew Lundy, Faical Ait-Benkhali, Jean Damascene Mbarubucyeye, Wlodek Kluzniak, Jorge Luis Flores, Ibrahim Torres, Jordan A. Goodman, Anita Reimer, Adam Otte, Eduardo Moreno Barbosa, M. J. Lang, Frank M. Rieger, Elijah Willox, Colin Adams, Pedro Miranda-Romagnoli, Louis Du Plessis, Andrea Albert, Orel Gueta, Anna Barnacka, Brenda Dingus, Gašper Kukec Mezek, Hazal Goksu, Jorge Cotzomi, William H. Lee, Ruben Alfaro, Glenn Sembroski, David A. Williams, Eduardo de la Fuente, Anu Kundu, Dezhi Huang, Brian Reville, Connor Duffy, Edna Ruiz-Velasco, Anna Luashvili, Alisha Chromey, Konstantin Pfrang, L. Giunti, Philip Kaaret, Maria Magdalena González, Olivier Hervet, Hermes Leon Vargas, Sébastien Le Stum, Amanda Weinstein, Aryeh Brill, James Davies, Ken Ragan, Santiago Pita, Juan Carlos Arteaga Velazquez, Jason Lee, Sabrina Einecke, Lukasz Stawarz, Iryna Lypova, Julie McEnery, Sara Coutiño de Leon, Dieter Horns, R. J. Tuffs, Christo Venter, Meghan Tanner, Monica Barnard, B. Bi, Yvonne Becherini, Colas Rivière, Iftach Sadeh, Lott Frans, Mischa Breuhaus, Pauline Chambery, C. Levy, Jose Luis García-Luna, Michelle Tsirou, D. Malyshev, Ramiro Torres Escobedo, Hassan Abdalla, Hambeleleni Ndiyavala, Chang Dong Rho, Jhilik Majumdar, Martin Pohl, Mathieu Bony, Oguzhan Anguener, Hend Yassin, Gwenael Giacinti, Manuel Meyer, Arturo Iriarte, John Matthews, Kirsty Feijen, Ahron S. Barber, Floriane Cangemi, Fernando Garfias, R. A. Ong, Thomas Weisgarber, Thomas Bylund, Gilgamesh Luis-Raya, Rowan Batzofin, Mathieu Naurois, Jacques Muller, Avery Archer, Andreas Quirrenbach, Anushka Udara Abeysekara, José Serna-Franco, Hugo Alberto Ayala Solares, Davit Zargaryan, Rubén López-Coto, Reshmi Mukherjee, Andreas Zmija, Guillem Marti'i-Devesa, Sameer Patel, M. Lemoine-Goumard, Roberto Noriega-Papaqui, Gaëtan Fichet de Clairfontaine, Axel Donath, A. W. Chen, Michael Kreter, Yunior Pérez Araujo, Anna Lia Longinotti, Michael Zacharias, Kleopas Shiningayamwe, Robert Brose, Fabian Schüssler, Emmanuel Moulin, Patrick Moriarty, Edna Ruiz Velasco, Michael Newbold, Oscar Chaparro-Amaro, J. T. Linnemann, Lenka Tomankova, Jodi Christiansen, Jaqueline Catalano, Ian James Watson, R. Konno, Andrew Taylor, C. Arcaro, Jason John Watson, Gavin Rowell, Daniel Omar Avila Rojas, Denys Malyshev, Emmet Roache, Rhiannon Turner, Chad Brisbois, Mohanraj Senniappan, José Roberto Angeles Camacho, Daniel Nieto, V. Poireau, Jimmy N.S. Shapopi, G. Vasileiadis, Hannah Dalgleish, donggeun tak, Juan Carlos Díaz Vélez, Armelle Jardin-Blicq, N. Zywucka, Abe Falcone, Nicola Omodei, Matthieu Renaud, German Hermann, Paul Morris, Maria Haupt, Stefan Klepser, Christopher van Eldik, Rafal Moderski, Alessandro Montanari, Amy Furniss, Sylvia Zhu, P. J. Meintjes, David Berge, Jose Andres Garcia-Gonzalez, Humberto Ibarguen Salazar, Wayne Robert Springer, Heike Prokoph, Marion Spir-Jacob, Amid Nayerhoda, Laboratoire d'Annecy de Physique des Particules (LAPP/Laboratoire d'Annecy-le-Vieux de Physique des Particules), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire d'Annecy de Physique des Particules (LAPP), Fermi-LAT, HAWC, H.E.S.S., MAGIC, and VERITAS
Subjects: Cherenkov detector, air, Cherenkov counter: water, Physics beyond the Standard Model, Astrophysics::High Energy Astrophysical Phenomena, Dark matter, satellite, FOS: Physical sciences, IACT, Astrophysics, 01 natural sciences, GLAST, dark matter, law.invention, law, HESS, 0103 physical sciences, 010306 general physics, Cherenkov radiation, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Annihilation, 010308 nuclear & particles physics, background, new physics, imaging, sensitivity, MAGIC, Galaxy, Automatic Keywords, annihilation, VERITAS, galaxy, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], statistical, HAWC, Fermi Gamma-ray Space Telescope
Abstract: 36th International Cosmic Ray Conference, ICRC2019, Madison, USA, 24 Jul 2019 - 1 Aug 2019; 9 pages (2019)., The search for Dark Matter (DM) has great potential to reveal physics beyond the Standard Model. As such, searches for evidence of DM particles are being carried out using a wide range of techniques, such as direct searches for DM particles, searches for DM produced with colliders, and indirect searches for the Standard Model annihilation products of DM. Dwarf spheroidal galaxies (dSphs) are excellent targets for indirect Dark Matter searches due to their relatively high DM content and negligible expected astrophysical background. A collaboration was formed to maximise the sensitivity of DM searches towards dSphs by combining for the first time dSph data from three imaging air Cherenkov telescope (IACT) arrays: HESS, MAGIC, and VERITAS; the Fermi-LAT satellite, and the water Cherenkov detector HAWC. Due to the diverse nature of the instruments involved, each experiment will analyse their individual datasets from multiple targets and then the results will be combined at the likelihood level. For consistency of the likelihoods across the five experiments, a common approach is used to treat the astrophysical factor (J-Factor) for each target and an agreed set of annihilation channels are considered. We also agree on a common statistical approach and treatment of instrumental systematic uncertainties. The results are presented in terms of constraints on the velocity-weighted cross section for DM self-annihilation as a function of the DM particle mass.
Published: 2019
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24. A Decade of Multiwavelength Observations of the TeV Blazar 1ES 1215+303: Extreme Shift of the Synchrotron Peak Frequency and Long-term Optical–Gamma-Ray Flux Increase

Author: Tuomas Savolainen, S. S. Scott, K. Nilsson, A. Wilhelm, Walter Max-Moerbeck, S. O'Brien, Alasdair E. Gent, Nahee Park, A. N. Otte, K. Ragan, R. A. Ong, G. H. Sembroski, K. Pfrang, Merja Tornikoski, T. J. Williamson, Wei Cui, Sebastian Kiehlmann, R. Shang, Marita Krause, Anushka Udara Abeysekara, Philip G. Edwards, Amy Furniss, P. Kaaret, A. Pichel, Gernot Maier, Alexander B. Pushkarev, D. Horan, Anne Lähteenmäki, Jamie Holder, V. V. Vassiliev, B. G. Piner, Lucy Fortson, A. Brill, P. Moriarty, Karlen Shahinyan, Tarek M. Hassan, Denis Bernard, J. H. Buckley, G. Hughes, M. Pohl, I. Sushch, M. Kertzman, A. C. S. Readhead, J. Valverde, Robert Brose, Wystan Benbow, Q. Feng, John L. Quinn, Daniel Nieto, Stephen Fegan, M. Nievas-Rosillo, D. Ribeiro, M. Buchovecky, Giuliana Noto, T. B. Humensky, Jenni Jormanainen, F. Krennrich, Talvikki Hovatta, M. J. Lang, A. Petrashyk, R. R. Prado, V. Fallah Ramazani, J. P. Finley, Jodi Christiansen, P. Wilcox, Olivier Hervet, A. J.R. Weinstein, A. D. Falcone, Matthew L. Lister, D. S. Hanna, N. Kelley-Hoskins, Ralph Bird, I. Sadeh, David A. Williams, Gordon T. Richards, A. Archer, E. Roache, D. B. Kieda, Orel Gueta, L. O. Takalo, G. H. Gillanders, Yuri Y. Kovalev, P. T. Reynolds, E. Lindfors, Marcos Santander, Reshmi Mukherjee, C. Giuri, R. M. Wells, E. Pueschel, Laboratoire Leprince-Ringuet (LLR), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Fermi-LAT, VERITAS, Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), University of Turku, Metsähovi Radio Observatory, Anne Lähteenmäki Group, Department of Electronics and Nanoengineering, Aalto-yliopisto, and Aalto University
Subjects: 010504 meteorology & atmospheric sciences, Infrared, Flux, Astrophysics, 4/3, 01 natural sciences, law.invention, law, Jets, Broadband, 010303 astronomy & astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Gamma ray, Optical polarization, Galaxies: active, gamma-rays, Synchrotron, Wavelength, gamma ray: emission, optical [polarization], infrared, BL Lacertae objects, VERITAS, Astrophysics - High Energy Astrophysical Phenomena, Gamma-rays, ON 325, jets, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, GLAST, blazar, X-ray, emission [gamma ray], synchrotron, 0103 physical sciences, polarization: optical, Blazar, 0105 earth and related environmental sciences, B2 1215+30, S3 1215+30), Astronomy and Astrophysics, flux, 13. Climate action, Space and Planetary Science, correlation, Active galaxies, ddc:520, blazars BL Lacertae objects: individ- ual: 1ES 1215+303 (Ton 605, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Blazars
Abstract: Blazars are known for their variability on a wide range of timescales at all wavelengths. Most studies of TeV gamma-ray blazars focus on short timescales, especially during flares. With a decade of observations from the Fermi-LAT and VERITAS, we present an extensive study of the long-term multi-wavelength radio-to-gamma-ray flux-density variability, with the addition of a couple of short-time radio-structure and optical polarization observations of the blazar 1ES 1215+303 (z=0.130), with a focus on its gamma-ray emission from 100 MeV to 30 TeV. Multiple strong GeV gamma-ray flares, a long-term increase in the gamma-ray and optical flux baseline and a linear correlation between these two bands are observed over the ten-year period. Typical HBL behaviors are identified in the radio morphology and broadband spectrum of the source. Three stationary features in the innermost jet are resolved by VLBA at 43.1, 22.2, and 15.3 GHz. We employ a two-component synchrotron self-Compton model to describe different flux states of the source, including the epoch during which an extreme shift in energy of the synchrotron peak frequency from infrared to soft X-rays is observed., Comment: Accepted for publication in the Astrophysical Journal
Published: 2020
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25. Muon Hunter: a Zooniverse project

Author: Amy Furniss, Lucy Fortson, R. A. Ong, J. Jarvis, I. Sadeh, M. K. Daniel, Ralph Bird, Reshmi Mukherjee, Hugh Dickinson, Q. Feng, and David A. Williams
Subjects: History, Artificial neural network, Event (computing), Calibration (statistics), Computer science, business.industry, media_common.quotation_subject, Machine learning, computer.software_genre, Convolutional neural network, Computer Science Applications, Education, Citizen science, sort, Artificial intelligence, Raw data, Function (engineering), business, computer, media_common
Abstract: The large datasets and often low signal-to-noise inherent to the raw data of modern astroparticle experiments calls out for increasingly sophisticated event classification techniques. Machine learning algorithms, such as neural networks, have the potential to outperform traditional analysis methods, but come with the major challenge of identifying reliably classified training samples from real data. Citizen science represents an effective approach to sort through the large datasets efficiently and meet this challenge. Muon Hunter is a project hosted on the Zooniverse platform, wherein volunteers sort through pictures of data from the VERITAS cameras to identify muon ring images. Each image is classified multiple times to produce a clean dataset used to train and validate a convolutional neural network model both able to reject background events and identify suitable calibration data to monitor the telescope performance as a function of time.
Published: 2020
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26. A Very High Energy gamma-Ray Survey toward the Cygnus Region of the Galaxy

Author: M. Buchovecky, Ralph Bird, R. A. Ong, M. K. Daniel, D. S. Hanna, P. Moriarty, A. Wilhelm, M. Kertzman, A. Weinstein, E. Pueschel, Marcos Santander, C. B. Rulten, A. Flinders, Maria Krause, R. M. Wells, A. N. Otte, John L. Quinn, Julien Rousselle, Q. Feng, S. McArthur, V. Bugaev, P. T. Reynolds, P. Kaaret, Gordon T. Richards, T. Aune, N. H. Park, G. Hughes, David Kieda, E. Roache, K. Huang, Vladimir Vassiliev, Gernot Maier, B. Zitzer, Moritz Hütten, Lucy Fortson, Olivier Hervet, Wystan Benbow, S. P. Wakely, M. J. Lang, C. A. Johnson, Martin Pohl, Amy Furniss, Abraham D. Falcone, Karlen Shahinyan, A. Archer, J. Tyler, Henrike Fleischhack, David A. Williams, K. Ragan, N. Kelley-Hoskins, Jamie Holder, Dirk Pandel, G. H. Sembroski, J. P. Finley, T. B. Humensky, R. Mukherjee, T. T.Y. Lin, A. Popkow, S. Kumar, P. Wilcox, Robert Brose, J. Grube, J. E. Ward, A. Petrashyk, P. Kar, Wei Cui, I. Sadeh, S. O'Brien, Anushka Udara Abeysekara, and Eric V. Gotthelf
Subjects: Physics, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Institut für Physik und Astronomie, Astronomy and Astrophysics, Context (language use), Cosmic ray, Quasar, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Pulsar wind nebula, Crab Nebula, Pulsar, 13. Climate action, Space and Planetary Science, 0103 physical sciences, ddc:530, Supernova remnant, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Fermi Gamma-ray Space Telescope
Abstract: We present results from deep observations towards the Cygnus region using 300 hours of very-high-energy (VHE) $\gamma$-ray data taken with the VERITAS Cherenkov telescope array and over seven years of high-energy $\gamma$-ray data taken with the Fermi satellite at an energy above 1 GeV. As the brightest region of diffuse $\gamma$-ray emission in the northern sky, the Cygnus region provides a promising area to probe the origins of cosmic rays. We report the identification of a potential Fermi-LAT counterpart to VER J2031+415 (TeV J2032+4130), and resolve the extended VHE source VER J2019+368 into two source candidates (VER J2018+367* and VER J2020+368*) and characterize their energy spectra. The Fermi-LAT morphology of 3FGL 2021.0+4031e (the Gamma-Cygni supernova remnant) was examined and a region of enhanced emission coincident with VER J2019+407 was identified and jointly fit with the VERITAS data. By modeling 3FGL J2015.6+3709 as two sources, one located at the location of the pulsar wind nebula CTB 87 and one at the quasar QSO J2015+371, a continuous spectrum from 1 GeV to 10 TeV was extracted for VER J2016+371 (CTB 87). An additional 71 locations coincident with Fermi-LAT sources and other potential objects of interest were tested for VHE $\gamma$-ray emission, with no emission detected and upper limits on the differential flux placed at an average of 2.3% of the Crab Nebula ux. We interpret these observations in a multiwavelength context and present the most detailed $\gamma$-ray view of the region to date., Comment: 49 Pages, 22 Figures, 13 Tables, Accepted to ApJ
Published: 2018

27. HESS J1943+213: An Extreme Blazar Shining through the Galactic Plane

Author: Amy Furniss, P. Pontrelli, Gordon T. Richards, A. Weinstein, Jamie Holder, A. N. Otte, M. Buchovecky, M. K. Daniel, Ralph Bird, Wystan Benbow, P. Kaaret, C. A. Johnson, Daniel Nieto, E. Pueschel, Maria Krause, I. Sadeh, O. M. Weiner, David Kieda, M. J. Lang, Wei Cui, R. A. Ong, Moritz Hütten, R. Mukherjee, Q. Feng, W. Brisken, P. T. Reynolds, Lucy Fortson, John L. Quinn, G. Hughes, Robert Brose, N. Kelley-Hoskins, D. S. Hanna, S. McArthur, T. T.Y. Lin, C. Rulten, V. Bugaev, A. Petrashyk, A. Flinders, P. Moriarty, O. Hervet, P. Kar, A. Popkow, P. Wilcox, E. Roache, A. Archer, R. M. Wells, Abraham D. Falcone, G. H. Sembroski, Karlen Shahinyan, David A. Williams, T. B. Humensky, G. H. Gillanders, M. Pohl, S. Kumar, J. P. Finley, S. P. Wakely, S. O'Brien, A. Wilhelm, N. H. Park, K. Ragan, J. Tyler, and F. Krennrich
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Astroparticle physics, Physics, Cosmology and Nongalactic Astrophysics (astro-ph.CO), European VLBI Network, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Galactic plane, 01 natural sciences, Redshift, Space and Planetary Science, 0103 physical sciences, Spectral energy distribution, ddc:520, Astrophysics - High Energy Astrophysical Phenomena, Blazar, 010303 astronomy & astrophysics, Very Long Baseline Array, Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, BL Lac object
Abstract: HESS J1943+213 is a very-high-energy (VHE; $>$100 GeV) $\gamma$-ray source in the direction of the Galactic Plane. Studies exploring the classification of the source are converging towards its identification as an extreme synchrotron BL Lac object. Here we present 38 hours of VERITAS observations of HESS J1943+213 taken over two years. The source is detected with $\sim$20 standard deviations significance, showing a remarkably stable flux and spectrum in VHE $\gamma$-rays. Multi-frequency very-long-baseline array (VLBA) observations of the source confirm the extended, jet-like structure previously found in the 1.6 GHz band with European VLBI Network and detect this component in the 4.6 GHz and the 7.3 GHz bands. The radio spectral indices of the core and the jet and the level of polarization derived from the VLBA observations are in a range typical for blazars. Data from VERITAS, $Fermi$-LAT, $Swift$-XRT, FLWO 48$''$ telescope, and archival infrared and hard X-ray observations are used to construct and model the spectral energy distribution (SED) of the source with a synchrotron-self-Compton model. The well-measured $\gamma$-ray peak of the SED with VERITAS and $Fermi$-LAT provides constraining upper limits on the source redshift. Possible contribution of secondary $\gamma$-rays from ultra-high-energy cosmic ray-initiated electromagnetic cascades to the $\gamma$-ray emission is explored, finding that only a segment of the VHE spectrum can be accommodated with this process. A variability search is performed across X-ray and $\gamma$-ray bands. No statistically significant flux or spectral variability is detected., Comment: Accepted for publication in The Astrophysical Journal
Published: 2018
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28. Multiwavelength observations of the blazar BL Lacertae: a new fast TeV gamma-ray flare

Author: A. A. Mokrushina, J. P. Finley, B. Zitzer, A. N. Otte, M. P. Connolly, A. Weinstein, M. K. Daniel, Alan P. Marscher, C. A. Johnson, T. B. Humensky, N. H. Park, Robert Brose, Svetlana G. Jorstad, P. T. Reynolds, P. Kaaret, Anne Lähteenmäki, S. Enestam, R. A. Ong, Paul S. Smith, K. Ragan, Lucy Fortson, T. T.Y. Lin, P. Wilcox, Merja Tornikoski, T. Brantseg, Wystan Benbow, C. Rulten, Talvikki Hovatta, G. H. Gillanders, A. Petrashyk, P. Moriarty, S. P. Wakely, Martin Pohl, Yuri Y. Kovalev, M. Hütten, P. Kar, Marcos Santander, E. Pueschel, G. H. Sembroski, Q. Feng, I. Agudo, Wei Cui, Amy Furniss, Matthew L. Lister, José L. Gómez, M. Buchovecky, Gordon T. Richards, Tuomas Savolainen, Alexander B. Pushkarev, I. Gunawardhana, P. Pontrelli, I. Sadeh, J. H. Buckley, Sol N. Molina, R. Mukherjee, Anushka Udara Abeysekara, G. Hughes, S. O'Brien, G. A. Borman, D. S. Hanna, Sebastian Kiehlmann, R. M. Wells, Jamie Holder, V. Bugaev, M. J. Lang, Wara Chamani, Ralph Bird, Valeri M. Larionov, S. McArthur, O. Hervet, David A. Williams, E. Roache, Abraham D. Falcone, Karlen Shahinyan, John L. Quinn, M. Kertzman, Frank Krennrich, Department of Energy (US), National Science Foundation (US), Smithsonian Institution, National Research Council of Canada, National Aeronautics and Space Administration (US), Russian Foundation for Basic Research, Russian Government, Alexander von Humboldt Foundation, Academy of Finland, Ministerio de Economía y Competitividad (España), European Commission, Junta de Andalucía, and Russian Science Foundation
Subjects: jets, Active galactic nucleus, active [Galaxies], Astrophysics::High Energy Astrophysical Phenomena, galaxies: active, bl lacertae objects: individual (bl lacertae = ver j2202+422), FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, law.invention, law, emission, 0103 physical sciences, high-frequencies, Blazar, 010303 astronomy & astrophysics, Very Long Baseline Array, polarimetric observations, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Superluminal motion, variability, 010308 nuclear & particles physics, Astronomy and Astrophysics, Quasar, black-hole mass, lac objects, Crab Nebula, Space and Planetary Science, active galactic nuclei, ddc:520, radio polarization, Astrophysics - High Energy Astrophysical Phenomena, individual (BL Lacertae = VER J2202+422) [BL Lacertae objects], energy, Flare, Radio wave
Abstract: Combined with measurements made by very-long-baseline interferometry, the observations of fast TeV gamma-ray flares probe the structure and emission mechanism of blazar jets. However, only a handful of such flares have been detected to date, and only within the last few years have these flares been observed from lower-frequency-peaked BL Lac objects and flat-spectrum radio quasars. We report on a fast TeV gamma-ray flare from the blazar BL Lacertae observed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS). with a rise time of ∼2.3 hr and a decay time of ∼36 min. The peak flux above 200 GeV is (4.2 ± 0.6) ×10 photon m s measured with a 4-minute-binned light curve, corresponding to ∼180% of the flux that is observed from the Crab Nebula above the same energy threshold. Variability contemporaneous with the TeV gamma-ray flare was observed in GeV gamma-ray, X-ray, and optical flux, as well as in optical and radio polarization. Additionally, a possible moving emission feature with superluminal apparent velocity was identified in Very Long Baseline Array observations at 43 GHz, potentially passing the radio core of the jet around the time of the gamma-ray flare. We discuss the constraints on the size, Lorentz factor, and location of the emitting region of the flare, and the interpretations with several theoretical models that invoke relativistic plasma passing stationary shocks.© 2018. The American Astronomical Society. All rights reserved., VERITAS is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation and the Smithsonian Institution, and by NSERC in Canada. We acknowledge the excellent work of the technical support staff at the Fred Lawrence Whipple Observatory and at the collaborating institutions in the construction and operation of the instrument. The research at Boston University was supported in part by NASA Fermi Guest Investigator Program grant 80NSSC17K 0694. The VLBA is an instrument of the Long Baseline Observatory (LBO). The LBO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This research has made use of data from the MOJAVE database that is maintained by the MOJAVE team (Lister et al. 2009) and supported by NASA Fermi grant NNX15AU76G. This work made use of the Swinburne University of Technology software correlator (Deller et al. 2011), developed as part of the Australian Major National Research Facilities Programme and operated under licence. Y.Y.K. and A.B.P. are partly supported by the Russian Foundation for Basic Research (project 17-02-00197), the government of the Russian Federation (agreement 05.Y09.21.0018), and the Alexander von Humboldt Foundation. T.S. was funded by the Academy of Finland projects 274477 and 284495. This research has made use of data from the OVRO 40 m monitoring program (Richards et al. 2011) which is supported in part by NASA grants NNX08AW31G, NNX11A043G, and NNX14AQ89G and NSF grants AST-0808050 and AST-1109911. The monitoring of BL. Lacertae and other blazars at the Steward Observatory is supported through NASA Fermi Guest Investigator grant NNX15AU81G. I.A. acknowledges support by a Ramon y Cajal grant of the Ministerio de Economia y Competitividad (MINECO) of Spain. Acquisition and reduction of the MAPCAT data was supported in part by MINECO through grants AYA2010-14844, AYA2013-40825-P, and AYA2016-80889-P, and by the Regional Government of Andalucia through grant P09-FQM-4784. The MAPCAT observations were carried out at the German-Spanish Calar Alto Observatory, which is jointly operated by the Max-Planck-Institut fur Astronomie and the Instituto de Astrofisica de Andalucia-CSIC. The St. Petersburg University team acknowledges support from Russian Science Foundation grant 17-12-01029.
Published: 2018
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29. Very-high-energy γ-ray observations of the blazar 1es 2344+514 with veritas

Author: A. Flinders, R. Mukherjee, P. Kaaret, E. Pueschel, A. McCann, D. S. Hanna, Martin Pohl, Maria Krause, Wei Cui, R. A. Ong, David Kieda, F. Krennrich, Daniel Nieto, M. K. Daniel, Wystan Benbow, A. N. Otte, Sinéad M. Griffin, M. P. Connolly, A. Wilhelm, A. Archer, Robert Brose, Moritz Hütten, Cameron H. Allen, J. Grube, C. Rulten, A. Petrashyk, G. H. Gillanders, Etienne Bourbeau, Lucy Fortson, N. H. Park, A. C. Rovero, P. Kar, P. T. Reynolds, N. Håkansson, Henrike Fleischhack, Gordon T. Richards, J. V. Tucci, Gernot Maier, M. Kertzman, A. O'Faolain de Bhroithe, J. Tyler, G. H. Sembroski, Matteo Cerruti, G. Hughes, J. H. Buckley, S. Archambault, M. Buchovecky, Amy Furniss, S. P. Wakely, S. O'Brien, I. Sadeh, A. Popkow, Marcos Santander, Thanh Huy Nguyen, J. V. Cardenzana, C. A. Johnson, K. Ragan, Jodi Christiansen, P. Moriarty, Xuhui Chen, M. Fernandez-Alonso, K. Meagher, Q. Feng, T. B. Humensky, J. P. Finley, John L. Quinn, S. Kumar, A. Pichel, E. Roache, Abraham D. Falcone, Karlen Shahinyan, Ralph Bird, S. McArthur, V. Bugaev, O. Hervet, J. D. Eisch, A. Weinstein, M. J. Lang, N. Kelley-Hoskins, I. Telezhinsky, Jamie Holder, and David A. Williams
Subjects: gamma-rays: galaxies, Point source, Ciencias Físicas, bl-lacertae objects, Astrophysics, telescope, 01 natural sciences, Spectral line, spectrum, purl.org/becyt/ford/1 [https], 0103 physical sciences, emission, ASTROPARTICLE PHYSICS, Blazar, 010303 astronomy & astrophysics, Physics, GALAXIES [GAMMA-RAYS], 010308 nuclear & particles physics, variability, Attenuation, Gamma ray, Astronomy, Institut für Physik und Astronomie, background-radiation, Astronomy and Astrophysics, purl.org/becyt/ford/1.3 [https], bl lacertae objects: individual: 1es 2344+514=verj2347+517, Light curve, Astronomía, radio, Extragalactic background light, x-ray, Space and Planetary Science, astroparticle physics, active galactic nuclei, ddc:520, BL LACERTAE OBJECTS, Astrophysics - High Energy Astrophysical Phenomena, constraints, CIENCIAS NATURALES Y EXACTAS, BL Lac object
Abstract: We present very-high-energy $\gamma$-ray observations of the BL Lac object 1ES 2344+514 taken by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) between 2007 and 2015. 1ES 2344+514 is detected with a statistical significance above background of $20.8\sigma$ in $47.2$ hours (livetime) of observations, making this the most comprehensive very-high-energy study of 1ES 2344+514 to date. Using these observations the temporal properties of 1ES 2344+514 are studied on short and long times scales. We fit a constant flux model to nightly- and seasonally-binned light curves and apply a fractional variability test, to determine the stability of the source on different timescales. We reject the constant-flux model for the 2007-2008 and 2014-2015 nightly-binned light curves and for the long-term seasonally-binned light curve at the $> 3\sigma$ level. The spectra of the time-averaged emission before and after correction for attenuation by the extragalactic background light are obtained. The observed time-averaged spectrum above 200 GeV is satisfactorily fitted (${\chi^2/NDF = 7.89/6}$) by a power-law function with index $\Gamma = 2.46 \pm 0.06_{stat} \pm 0.20_{sys} $ and extends to at least 8 TeV. The extragalactic-background-light-deabsorbed spectrum is adequately fit (${\chi^2/NDF = 6.73/6}$) by a power-law function with index $\Gamma = 2.15 \pm 0.06_{stat} \pm 0.20_{sys} $ while an F-test indicates that the power-law with exponential cutoff function provides a marginally-better fit ($\chi^2/NDF $ = $2.56 / 5 $) at the 2.1$\sigma$ level. The source location is found to be consistent with the published radio location and its spatial extent is consistent with a point source., Comment: 7 pages, 2 figures. Published in Monthly Notices of the Royal Astronomical Society
Published: 2017
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30. Dark Matter Constraints from a Joint Analysis of Dwarf Spheroidal Galaxy Observations with VERITAS

Author: Ralph Bird, Q. Feng, Marita Krause, Martin Pohl, M. J. Lang, J. Tyler, Matteo Cerruti, J. H. Buckley, A. N. Otte, Amy Furniss, I. Telezhinsky, E. Roache, Jamie Holder, M. P. Connolly, Wystan Benbow, N. Kelley-Hoskins, P. Kaaret, Olivier Hervet, Alex Geringer-Sameth, Karlen Shahinyan, B. Zitzer, J. Grube, M. Buchovecky, G. H. Sembroski, F. Krennrich, S. McArthur, N. H. Park, David Kieda, C. B. Rulten, P. Kar, Etienne Bourbeau, T. T.Y. Lin, N. Håkansson, Henrike Fleischhack, J. V. Tucci, A. Popkow, C. A. Johnson, M. Kertzman, Sinéad M. Griffin, R. Mukherjee, P. Moriarty, S. P. Wakely, Karen Byrum, R. A. Ong, Lucy Fortson, A. Weinstein, Marcos Santander, B. Hummensky, M. K. Daniel, John L. Quinn, T. Brantseg, E. Pueschel, David A. Williams, Gordon T. Richards, P. T. Reynolds, K. Ragan, Daniel Nieto, Moritz Hütten, A. Archer, D. Staszak, S. Trepanier, Jodi Christiansen, P. Wilcox, I. Sadeh, Wei Cui, Savvas M. Koushiappas, A. W. Smith, J. P. Finley, S. Archambault, D. S. Hanna, V. Bugaev, S. O'Brien, and G. Hughes
Subjects: particle, Astrophysics::High Energy Astrophysical Phenomena, Dark matter, FOS: Physical sciences, IACT, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Bottom quark, models, gamma-ray astronomy, 0103 physical sciences, ddc:530, 010303 astronomy & astrophysics, milky-way, Astrophysics::Galaxy Astrophysics, Dwarf galaxy, Physics, parameters, High Energy Astrophysical Phenomena (astro-ph.HE), Gauge boson, Annihilation, 010308 nuclear & particles physics, Astronomy, Institut für Physik und Astronomie, Dwarf spheroidal galaxy, kinematics, Weakly interacting massive particles, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present constraints on the annihilation cross section of WIMP dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of $\sim$230 hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is $1.35\times 10^{-23} {\mathrm{ cm^3s^{-1}}}$ at 1 TeV for the bottom quark ($b\bar{b}$) final state, $2.85\times 10^{-24}{\mathrm{ cm^3s^{-1}}}$ at 1 TeV for the tau lepton ($\tau^{+}\tau^{-}$) final state and $1.32\times 10^{-25}{\mathrm{ cm^3s^{-1}}}$ at 1 TeV for the gauge boson ($\gamma\gamma$) final state., Comment: 14 pages, 9 figures, published in PRD, Ascii tables containing annihilation cross sections limits are available for download as ancillary files with readme.txt file description of limits
Published: 2017
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31. Gamma-ray observations of tycho’s supernova remnant with veritas andfermi

Author: Q. Feng, P. T. Reynolds, C. A. Johnson, Wystan Benbow, A. Popkow, J. P. Finley, D. S. Hanna, B. Zitzer, Manel Errando, S. Kumar, D. B. Kieda, Karlen Shahinyan, Daniel Nieto, Henrike Fleischhack, Gernot Maier, Lucy Fortson, Moritz Hütten, David A. Williams, S. O'Brien, J. Tyler, M. Pohl, P. Kaaret, R. A. Ong, Thomas Weisgarber, Nahee Park, S. McArthur, J. H. Buckley, G. H. Sembroski, I. Sadeh, P. Wilcox, I. Telezhinsky, Jamie Holder, John L. Quinn, E. Pueschel, M. Buchovecky, P. Moriarty, P. Kar, A. N. Otte, S. Trepanier, Patrick Slane, A. J.R. Weinstein, A. Wilhelm, Ralph Bird, M. P. Connolly, D. Staszak, K. Ragan, Wei Cui, A. Archer, Gordon T. Richards, M. J. Lang, Marcos Santander, E. Roache, A. D. Falcone, Etienne Bourbeau, S. Archambault, Reshmi Mukherjee, Dwarkadas, N. Kelley-Hoskins, Bugaev, Matteo Cerruti, Amy Furniss, Sinéad M. Griffin, M. Kertzman, A. McCann, S. P. Wakely, and Marita Krause
Subjects: molecular cloud, shock acceleration, Astrophysics::High Energy Astrophysical Phenomena, stars-supernovae, cosmic-rays, Astrophysics, Type (model theory), telescope, 01 natural sciences, 0103 physical sciences, emission, ddc:530, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Spectral index, Range (particle radiation), particle-acceleration, 010308 nuclear & particles physics, brahes 1572 supernova, data behind figure, Gamma ray, Center (category theory), magnetic-field, electrons, Institut für Physik und Astronomie, individual(tycho's snr) supporting material, Astronomy and Astrophysics, gamma rays, Supernova, Space and Planetary Science, ddc:520, High Energy Physics::Experiment, high-energy, Energy (signal processing), Fermi Gamma-ray Space Telescope
Abstract: The astrophysical journal 836(1), 23 (2017). doi:10.3847/1538-4357/836/1/23, High-energy gamma-ray emission from supernova remnants (SNRs) has provided a unique perspective for studies of Galactic cosmic-ray acceleration. Tycho's SNR is a particularly good target because it is a young, type Ia SNR that has been well-studied over a wide range of energies and located in a relatively clean environment. Since the detection of gamma-ray emission from Tycho's SNR by VERITAS and Fermi-LAT, there have been several theoretical models proposed to explain its broadband emission and high-energy morphology. We report on an update to the gamma-ray measurements of Tycho's SNR with 147 hr of VERITAS and 84 months of Fermi-LAT observations, which represent about a factor of two increase in exposure over previously published data. About half of the VERITAS data benefited from a camera upgrade, which has made it possible to extend the TeV measurements toward lower energies. The TeV spectral index measured by VERITAS is consistent with previous results, but the expanded energy range softens a straight power-law fit. At energies higher than 400 GeV, the power-law index is 2.92 ± 0.42$_{stat}$ ± 0.20$_{sys}$. It is also softer than the spectral index in the GeV energy range, 2.14 ± 0.09$_{stat}$ ± 0.02$_{sys}$, measured in this study using Fermi-LAT data. The centroid position of the gamma-ray emission is coincident with the center of the remnant, as well as with the centroid measurement of Fermi-LAT above 1 GeV. The results are consistent with an SNR shell origin of the emission, as many models assume. The updated spectrum points to a lower maximum particle energy than has been suggested previously., Published by IOP Publ., Chicago, Ill. [u.a.]
Published: 2017
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32. Gamma-ray Observations Under Bright Moonlight with VERITAS

Author: G. H. Gillanders, A. Weinstein, Martin Pohl, M. Kertzman, S. McArthur, Sinéad M. Griffin, Wystan Benbow, O. Hervet, P. Moriarty, Henrike Fleischhack, Q. Feng, A. Popkow, John L. Quinn, P. Kaaret, M. J. Lang, D. S. Hanna, David Kieda, Gordon T. Richards, Lucy Fortson, R. A. Ong, Ralph Bird, P. T. Reynolds, J. P. Finley, Wei Cui, J. V. Cardenzana, E. Pueschel, Maria Krause, David A. Williams, M. Buchovecky, C. A. Johnson, N. H. Park, Daniel Nieto, E. Roache, L. Ciupik, A. Bouvier, Gernot Maier, Abraham D. Falcone, M. K. Daniel, S. P. Wakely, A. N. Otte, Karlen Shahinyan, S. Archambault, S. O'Brien, K. Ragan, I. Telezhinsky, Jamie Holder, Matteo Cerruti, Amy Furniss, M. P. Connolly, G. Hughes, Etienne Bourbeau, B. Zitzer, A. Archer, T. T.Y. Lin, G. H. Sembroski, T. B. Humensky, Moritz Hütten, Manel Errando, I. Sadeh, R. Mukherjee, D. Staszak, S. Trepanier, P. Wilcox, V. Bugaev, C. Rulten, and P. Kar
Subjects: Moonlight, Astrophysics and Astronomy, Photomultiplier, Instrumentation, FOS: Physical sciences, IACT, Astrophysics, telescope, 01 natural sciences, law.invention, moon, iact, Positron, law, veritas, 0103 physical sciences, ddc:530, crab-nebula, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Cherenkov radiation, Physics, instrumentation, 010308 nuclear & particles physics, Gamma ray, Institut für Physik und Astronomie, Astronomy and Astrophysics, moonlight, radiation, 13. Climate action, ddc:540, ddc:520, observing methods, Astrophysics - Instrumentation and Methods for Astrophysics, astro-ph.IM, Flare
Abstract: Astroparticle physics 91, 34 - 43 (2017). doi:10.1016/j.astropartphys.2017.03.001, Imaging atmospheric Cherenkov telescopes (IACTs) are equipped with sensitive photomultiplier tube (PMT) cameras. Exposure to high levels of background illumination degrades the efficiency of and potentially destroys these photo-detectors over time, so IACTs cannot be operated in the same configuration in the presence of bright moonlight as under dark skies. Since September 2012, observations have been carried out with the VERITAS IACTs under bright moonlight (defined as about three times the night-sky-background (NSB) of a dark extragalactic field, typically occurring when Moon illumination > 35%) in two observing modes, firstly by reducing the voltage applied to the PMTs and, secondly, with the addition of ultra-violet (UV) bandpass filters to the cameras. This has allowed observations at up to about 30 times previous NSB levels (around 80% Moon illumination), resulting in 30% more observing time between the two modes over the course of a year. These additional observations have already allowed for the detection of a flare from the 1ES 1727 + 502 and for an observing program targeting a measurement of the cosmic-ray positron fraction. We provide details of these new observing modes and their performance relative to the standard VERITAS observations., Published by Elsevier, Amsterdam [u.a.]
Published: 2017
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33. On the Redshifts of the BL Lac 3FGL J0909.0+2310 and its Close Companion

Author: Itziar Aretxaga, J. León Tavares, Elena Terlevich, Roberto Terlevich, S. Coutiño de León, Olga Vega, Anna Lia Longinotti, J. Becerra González, Daniel Rosa-Gonzalez, Jairo Méndez-Abreu, Amy Furniss, Y. D. Mayya, and A. Carraminana
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Gran Telescopio Canarias, Physics, 010308 nuclear & particles physics, Angular distance, FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, Astrophysics, Nuclear activity, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Galaxy, Redshift, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Spectrograph, BL Lac object
Abstract: We report on the redshift of the BL Lac object 3FGL J0909.0+2310 based on observations obtained with the OSIRIS Multi Object Spectrograph (MOS) mounted on the 10.4-m Gran Telescopio Canarias. A redshift of 0.432+/-0.002 was obtained by the identification of three absorption features (CaII K&H and G-band) detected in the spectrum of the BL Lac host galaxy. The closest object to the BL Lac at an angular separation of 3.8" (~21 kpc at this distance) has a similar redshift of 0.431+/-0.002. This companion galaxy could be the most likely cause of the nuclear activity as postulated by studies based on more extended data sets and cosmological models. MOS allows us to study the object's neighbourhood within a field of view of approximately 7'x2' and we find two small groups of galaxies at redshifts 0.28 and 0.39 which are probably not related to the activity of 3FGL~J0909.0+2310., Accepted by MNRAS, 2016 November 30
Published: 2016

34. First study of Mrk501 through the eyes of NuSTAR, VERITAS and the $\textit{LIDAR-corrected}$ eyesight of MAGIC

Author: Greg Madejski, Koji Noda, Amy Furniss, David Paneque, and Josefa González
Subjects: media_common.quotation_subject, Astronomy, law.invention, Telescope, Lidar, Sky, law, International Cosmic Ray Conference, Environmental science, Satellite, MAGIC (telescope), Blazar, Cherenkov radiation, media_common
Abstract: aMax-Planck-Institut fur Physik, Germany bStanford University, USA cNASA Goddard Space Flight Center, USA dInstituto de Astrofisica de Canarias, Spain E-mail: knoda@mppmu.mpg.de The blazar Mrk 501 is among the brightest X-ray and TeV sources in the sky, and among the few sources whose (radio to Very-High-Energy (VHE; ≥ 100 GeV) gamma-rays) spectral energy distributions can be characterized by current instruments by means of relatively short observations (minutes to hours). In 2013, we organized an extensive multi-instrument campaign involving the participation of Fermi-LAT, MAGIC, VERITAS, F-GAMMA, Swift, GASP-WEBT, and other collaborations/groups and instruments which provided the most detailed temporal and energy coverage on Mrk 501 to date. This observing campaign included, for the first time, observations with the Nuclear Stereoscopic Telescope Array (NuSTAR), which is a satellite mission launched in mid-2012. NuSTAR provides unprecedented sensitivity in the hard X-ray range 3-79 keV, which, together with MAGIC and VERITAS observations, is crucial to probe the highest energy electrons in Mrk 501. The multi-instrument campaign covered a few day long flaring activity in July 2013 which could be studied with strictly simultaneous NuSTAR and MAGIC observations. A large fraction of the MAGIC data during this flaring activity was affected by hazy atmospheric conditions, due to the presence of a sand layer from the Saharan desert. These data would have been removed in any standard Cherenkov Telescope data analysis. The MAGIC collaboration has developed a technique to correct for adverse atmospheric conditions the very high energy (VHE, E > 100 GeV) observations performed by Cherenkov telescopes. The technique makes use of the atmospheric information from the LIDAR facility that is operational at the MAGIC site, and applies an event-by-event correction to recover data affected by adverse weather conditions. This is the first time that LIDAR information has been used to produce a physics result with Cherenkov Telescope data taken during adverse atmospheric conditions, and hence sets a precedent for current and future ground-based gamma-ray instruments. In this contribution we report the observational results, focusing on the LIDAR-corrected MAGIC data and the strictly simultaneous NuSTAR and MAGIC/VERITAS data, and discuss the scientific implications. The 34th International Cosmic Ray Conference, 30 July6 August, 2015 The Hague, The Netherlands
Published: 2016
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35. Discovery of very high energy gamma rays from 1es 1440+122

Author: A. N. Otte, Geza Gyuk, E. Roache, M. P. Connolly, J. V. Tucci, Gernot Maier, S. P. Wakely, Abraham D. Falcone, Karlen Shahinyan, Wystan Benbow, N. Håkansson, Anna Barnacka, P. T. Reynolds, R. A. Ong, John L. Quinn, Ralph Bird, S. T. Griffiths, K. Sweeney, I. Telezhinsky, Jamie Holder, S. Federici, Martin Pohl, N. H. Park, J. Millis, J. Dumm, B. Zitzer, G. H. Sembroski, J. Grube, P. Kar, S. Godambe, Manel Errando, M. Kertzman, R. Welsing, M. J. Lang, L. C. Reyes, S. Kumar, K. Berger, Hugh Dickinson, D. S. Hanna, Xuhui Chen, Matteo Cerruti, Amy Furniss, Wei Cui, Henric Krawczynski, Y. Khassen, A. McCann, Q. Feng, A. O'Faolain de Bhroithe, David A. Williams, P. Kaaret, Lucy Fortson, D. Staszak, A. Popkow, Vladimir Vassiliev, H. Prokoph, Matthias Beilicke, J. S. Perkins, E. Pueschel, Markus Böttcher, J. Tyler, A. Wilhelm, A. Varlotta, A. Archer, J. V. Cardenzana, C. A. Johnson, E. Collins-Hughes, G. Hughes, David Kieda, Jodi Christiansen, J. D. Eisch, J. P. Finley, G. H. Gillanders, T. J. N. Nelson, S. McArthur, S. Griffin, K. Meagher, Jean-Francois Rajotte, S. Archambault, L. Ciupik, K. Ragan, V. Bugaev, H. Fleischhack, J. H. Buckley, A. W. Smith, A. S Madhavan, Gordon T. Richards, B. Behera, Daniel Nieto, and P. Moriarty
Subjects: extragalactic background light, multiwavelength observations, Astrophysics::High Energy Astrophysical Phenomena, bl-lacertae objects, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, bright blazars, 01 natural sciences, 7. Clean energy, law.invention, Telescope, law, 0103 physical sciences, intergalactic magnetic-field, Blazar, 010303 astronomy & astrophysics, Cherenkov radiation, Astrophysics::Galaxy Astrophysics, bl lacertae objects: general, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, tev blazars, Gamma ray, Astronomy, Institut für Physik und Astronomie, Astronomy and Astrophysics, source catalog, gamma-rays: general, Redshift, large-area telescope, einstein slew survey, Crab Nebula, 13. Climate action, Space and Planetary Science, active galactic nuclei, ddc:520, High Energy Physics::Experiment, Astrophysics - High Energy Astrophysical Phenomena, BL Lac object, Fermi Gamma-ray Space Telescope
Abstract: The BL Lacertae object 1ES 1440+122 was observed in the energy range from 85 GeV to 30 TeV by the VERITAS array of imaging atmospheric Cherenkov telescopes. The observations, taken between 2008 May and 2010 June and totalling 53 hours, resulted in the discovery of $\gamma$-ray emission from the blazar, which has a redshift $z$=0.163. 1ES 1440+122 is detected at a statistical significance of 5.5 standard deviations above the background with an integral flux of (2.8$\pm0.7_{\mathrm{stat}}\pm0.8_{\mathrm{sys}}$) $\times$ 10$^{-12}$ cm$^{-2}$ s$^{-1}$ (1.2\% of the Crab Nebula's flux) above 200 GeV. The measured spectrum is described well by a power law from 0.2 TeV to 1.3 TeV with a photon index of 3.1 $\pm$ 0.4$_{\mathrm{stat}}$ $\pm$ 0.2$_{\mathrm{sys}}$. Quasi-simultaneous multi-wavelength data from the Fermi Large Area Telescope (0.3--300 GeV) and the Swift X-ray Telescope (0.2--10 keV) are additionally used to model the properties of the emission region. A synchrotron self-Compton model produces a good representation of the multi-wavelength data. Adding an external-Compton or a hadronic component also adequately describes the data., Comment: 8 pages, 4 figures. Accepted for publication in MNRAS
Published: 2016
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36. A search for brief optical flashes associated with the seti target kic 8462852

Author: M. Buchovecky, Q. Feng, J. Grube, I. Telezhinsky, Jamie Holder, S. O'Brien, P. T. Reynolds, A. McCann, P. Fortin, Ralph Bird, Hugh Dickinson, Wystan Benbow, Anushka Udara Abeysekara, S. Archambault, Reshmi Mukherjee, A. Archer, D. Staszak, Martin Pohl, A. N. Otte, K. Meagher, S. McArthur, E. Pueschel, Maria Krause, O. M. Weiner, D. J. Fegan, Karen Byrum, J. D. Eisch, Abraham D. Falcone, Daniel Nieto, A. Weinstein, Karlen Shahinyan, S. Vincent, G. H. Gillanders, N. H. Park, D. S. Hanna, L. Ciupik, David A. Williams, N. Håkansson, Henrike Fleischhack, P. Kaaret, J. V. Cardenzana, J. V. Tucci, M. J. Lang, Moritz Hütten, Gernot Maier, John L. Quinn, N. Kelley-Hoskins, C. A. Johnson, K. Ragan, Geza Gyuk, Lucy Fortson, S. P. Wakely, R. A. Ong, David Kieda, F. Krennrich, Sinéad M. Griffin, J. Tyler, Matteo Cerruti, J. H. Buckley, Amy Furniss, Gordon T. Richards, E. Roache, P. Moriarty, J. P. Finley, G. Ratliff, Xuhui Chen, J. S. Perkins, Jodi Christiansen, T. B. Humensky, G. H. Sembroski, B. Zitzer, Manel Errando, S. Kumar, T. T.Y. Lin, A. Popkow, M. Kertzman, A. O'Faolain de Bhroithe, Wei Cui, A. Petrashyk, P. Kar, Marcos Santander, and ~
Subjects: stars, Photon, spectra, Astrophysics::High Energy Astrophysical Phenomena, astrobiology, FOS: Physical sciences, system, 01 natural sciences, oseti, extraterrestrial intelligence, law.invention, Telescope, Physics::Popular Physics, techniques: photometric, Observatory, law, veritas, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Pulse intensity, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Cherenkov radiation, Search for extraterrestrial intelligence, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, bursts, Extraterrestrial intelligence, Astrophysics::Instrumentation and Methods for Astrophysics, Institut für Physik und Astronomie, Astronomy, Astronomy and Astrophysics, telescopes, stars: individual ( kic 8462852), Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, ddc:520, Astrophysics::Earth and Planetary Astrophysics, methods: observational, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The astrophysical journal / 2 818(2), L33(2016). doi:10.3847/2041-8205/818/2/L33, The F-type star KIC 8462852 has recently been identified as an exceptional target for search for extraterrestrial intelligence (SETI) observations. We describe an analysis methodology for optical SETI, which we have used to analyze nine hours of serendipitous archival observations of KIC 8462852 made with the VERITAS gamma-ray observatory between 2009 and 2015. No evidence of pulsed optical beacons, above a pulse intensity at the Earth of approximately $1\;\mathrm{photon}\;{{\rm{m}}}^{-2}$, is found. We also discuss the potential use of imaging atmospheric Cherenkov telescope arrays in searching for extremely short duration optical transients in general., Published by Institute of Physics Publ., London
Published: 2016
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37. A search for very high energy gamma rays from the missing link binary pulsar J1023+0038 with VERITAS

Author: Wystan Benbow, John L. Quinn, A. Petrashyk, M. J. Lang, P. Kar, O. M. Weiner, Jonathan Biteau, J. P. Finley, B. Zitzer, N. Håkansson, Henrike Fleischhack, David Kieda, A. W. Smith, A. Flinders, Q. Feng, Abraham D. Falcone, Gordon T. Richards, E. Roache, Karlen Shahinyan, E. Pueschel, Geza Gyuk, S. Vincent, Nahee Park, A. Varlotta, N. Kelley-Hoskins, T. B. Humensky, Maria Krause, P. Moriarty, K. L. Byrum, Wei Cui, J. Grube, P. Kaaret, J. V. Cardenzana, J. D. Eisch, S. McArthur, A. McCann, Xuhui Chen, V. Bugaev, L. Ciupik, S. Archambault, Reshmi Mukherjee, Daniel Nieto, A. O'Faolain de Bhroithe, Sinéad M. Griffin, A. Popkow, E. Aliu, Maria Chernyakova, Lucy Fortson, J. Tyler, Matteo Cerruti, Moritz Hütten, J. H. Buckley, R. A. Ong, A. N. Otte, Amy Furniss, Marcos Santander, M. Kertzman, Martin Pohl, S. P. Wakely, P. Fortin, V. Pelassa, C. B. Rulten, Ralph Bird, G. H. Sembroski, A. Loo, K. Meagher, Hugh Dickinson, Mallory S. E. Roberts, M. Buchovecky, M. P. Connolly, D. Pandel, P. T. Reynolds, A. J.R. Weinstein, C. A. Johnson, J. V. Tucci, Gernot Maier, A. Wilhelm, D. Staszak, K. Ragan, I. Telezhinsky, Jamie Holder, David A. Williams, Thanh Huy Nguyen, A. Archer, and G. H. Gillanders
Subjects: nustar observations, Astrophysics::High Energy Astrophysical Phenomena, Flux, Binary number, FOS: Physical sciences, Astrophysics, telescope, 01 natural sciences, Binary pulsar, Pulsar, pulsars: general, psr j1023+0038, emission, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Millisecond, state change, 010308 nuclear & particles physics, pulsars: individual (psr j1023+0038), periastron, Gamma ray, transition, Institut für Physik und Astronomie, Astronomy and Astrophysics, gamma rays: general, 1st j102347.6+003841, Magnetic field, Neutron star, binaries: general, 13. Climate action, Space and Planetary Science, ddc:520, Astrophysics - High Energy Astrophysical Phenomena, millisecond pulsar, discovery
Abstract: The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259--63/LS 2883, making it an ideal candidate for the study of high-energy non-thermal emission. It has been the subject of multi-wavelength campaigns following the disappearance of the pulsed radio emission in 2013 June, which revealed the appearance of an accretion disk around the neutron star. We present the results of very high-energy gamma-ray observations carried out by VERITAS before and after this change of state. Searches for steady and pulsed emission of both data sets yield no significant gamma-ray signal above 100 GeV, and upper limits are given for both a steady and pulsed gamma-ray flux. These upper limits are used to constrain the magnetic field strength in the shock region of the PSR J1023+0038 system. Assuming that very high-energy gamma rays are produced via an inverse-Compton mechanism in the shock region, we constrain the shock magnetic field to be greater than $\sim$2 G before the disappearance of the radio pulsar and greater than $\sim$10 G afterwards., 7 pages, 3 figures, accepted for publication in ApJ
Published: 2016
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38. VERITAS and multiwavelength observations of the BL Lacertae object 1ES 1741+196

Author: J. V. Cardenzana, J. Biteau, C. A. Johnson, A. McCann, N. Kelley-Hoskins, K. Reynolds, R. A. Ong, Sinéad M. Griffin, D. Petry, D. S. Hanna, A. N. Otte, M. P. Connolly, Lucy Fortson, P. Kaaret, S. McArthur, V. Bugaev, J. Tyler, E. Roache, J. P. Finley, David Kieda, J. H. Buckley, B. Zitzer, A. Archer, F. Krennrich, G. H. Gillanders, J. Grube, G. Ratliff, Wystan Benbow, Manel Errando, A. Flinders, M. J. Lang, Xuhui Chen, Q. Feng, Abraham D. Falcone, Karlen Shahinyan, A. Popkow, E. Pueschel, Maria Krause, M. Huetten, O. M. Weiner, M. Kertzman, M. Buchovecky, A. O'Faolain de Bhroithe, Karen Byrum, J. D. Eisch, A. Weinstein, K. Meagher, Henrike Fleischhack, A. W. Smith, T. B. Humensky, S. Archambault, Martin Pohl, Gordon T. Richards, Geza Gyuk, P. Fortin, Marcos Santander, J. Dumm, Ralph Bird, Jodi Christiansen, John L. Quinn, P. T. Reynolds, C. B. Rulten, Matteo Cerruti, Amy Furniss, P. Moriarty, Daniel Nieto, L. Ciupik, K. Ragan, A. Wilhelm, S. Vincent, Hugh Dickinson, N. H. Park, S. O'Brien, J. V. Tucci, Gernot Maier, S. P. Wakely, R. Mukherjee, Anushka Udara Abeysekara, V. Pelassa, A. Petrashyk, P. Kar, G. H. Sembroski, David A. Williams, D. Staszak, I. Telezhinsky, Jamie Holder, L. C. Reyes, and Wei Cui
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Flux, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, telescope, 01 natural sciences, law.invention, Telescope, swift, law, gamma-ray astronomy, 0103 physical sciences, Blazar, 010303 astronomy & astrophysics, relativistic processes, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Spectral index, 010308 nuclear & particles physics, tev blazars, Institut für Physik und Astronomie, Astronomy, Astronomy and Astrophysics, Gamma-ray astronomy, source catalog, lac objects, spectral energy-distributions, Crab Nebula, x-ray, Space and Planetary Science, astroparticle physics, Spectral energy distribution, ddc:520, High Energy Physics::Experiment, Astrophysics - High Energy Astrophysical Phenomena, fermi, galaxies: individual: 1es 1741+196=ver j1744+195, discovery, BL Lac object
Abstract: Monthly notices of the Royal Astronomical Society 459(3), 2550 - 2557 (2016). doi:10.1093/mnras/stw664, We present results from multiwavelength observations of the BL Lacertae object 1ES 1741 + 196, including results in the very high energy γ-ray regime using the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The VERITAS time-averaged spectrum, measured above 180 GeV, is well modelled by a power law with a spectral index of 2.7 ± 0.7$_{stat}$ ± 0.2syst. The integral flux above 180 GeV is (3.9 ± 0.8$_{stat}$ ± 1.0$_{syst}$) × 10$^{−8}$ m$^{−2}$ s$^{−1}$, corresponding to 1.6 per cent of the Crab nebula flux on average. The multiwavelength spectral energy distribution of the source suggests that 1ES 1741+196 is an extreme-high-frequency-peaked BL Lacertae object. The observations analysed in this paper extend over a period of six years, during which time no strong flares were observed in any band. This analysis is therefore one of the few characterizations of a blazar in a non-flaring state., Published by Oxford Univ. Press, Oxford
Published: 2016
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39. A search of CO emission lines in blazars: the low molecular gas content of BL Lac objects compared to quasars

Author: J. Xavier Prochaska, Miroslava Dessauges-Zavadsky, Kyle F. Kaplan, M. Hogan, Michele Fumagalli, Amy Furniss, and David A. Williams
Subjects: Physics, education.field_of_study, Active galactic nucleus, 010308 nuclear & particles physics, Population, Astronomy and Astrophysics, Quasar, Astrophysics, 01 natural sciences, Galaxy, Redshift, Extragalactic background light, 13. Climate action, Space and Planetary Science, 0103 physical sciences, Intergalactic travel, education, Blazar, 010303 astronomy & astrophysics
Abstract: BL Lacertae (Lac) objects that are detected at very-high energies (VHE) are of fundamental importance to study multiple astrophysical processes, including the physics of jets, the properties of the extragalactic background light and the strength of the intergalactic magnetic field. Unfortunately, since most blazars have featureless optical spectra that preclude a redshift determination, a substantial fraction of these VHE extragalactic sources cannot be used for cosmological studies. To assess whether molecular lines are a viable way to establish distances, we have undertaken a pilot program at the IRAM 30m telescope to search for CO lines in three BL Lac objects with known redshifts. We report a positive detection of M_H2 ~ 3x10^8 Msun toward 1ES 1959+650, but due to the poor quality of the baseline, this value is affected by a large systematic uncertainty. For the remaining two sources, W Comae and RGB J0710+591, we derive 3sigma upper limits at, respectively, M_H2 < 8.0x10^8 Msun and M_H2 < 1.6x10^9 Msun, assuming a line width of 150 km/s and a standard conversion factor alpha=4 M_sun/(K km/s pc^2). If these low molecular gas masses are typical for blazars, blind redshift searches in molecular lines are currently unfeasible. However, deep observations are still a promising way to obtain precise redshifts for sources whose approximate distances are known via indirect methods. Our observations further reveal a deficiency of molecular gas in BL Lac objects compared to quasars, suggesting that the host galaxies of these two types of active galactic nuclei (AGN) are not drawn from the same parent population. Future observations are needed to assess whether this discrepancy is statistically significant, but our pilot program shows how studies of the interstellar medium in AGN can provide key information to explore the connection between the active nuclei and the host galaxies.
Published: 2012
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40. Gamma rays from the quasar PKS 1441+25: story of an escape

Author: Wystan Benbow, S. McArthur, O. M. Weiner, N. Håkansson, Henrike Fleischhack, M. J. Lang, P. Fortin, Ralph Bird, N. Kelley-Hoskins, L. Ciupik, R. Reeves, Geza Gyuk, Paul S. Smith, G. M. Madejski, Martin Pohl, Thomas W.-S. Holoien, A. O'Faolain de Bhroithe, J. Grube, Matthew J. Graham, R. A. Ong, A. McCann, K. Ragan, A. Petrashyk, K. Meagher, E. Pueschel, Marcos Santander, A. Wilhelm, Maria Krause, P. Kar, Benjamin J. Shappee, Talvikki Hovatta, S. G. Djorgovski, Paolo De Coppi, J. Tyler, M. P. Connolly, A. A. Mahabal, G. Ratliff, A. Archer, Xuhui Chen, J. H. Buckley, Lucy Fortson, Jodi Christiansen, S. Archambault, Q. Feng, P. Moriarty, Anthony C. S. Readhead, V. V. Vassiliev, A. Flinders, J. S. Perkins, Reshmi Mukherjee, Abraham D. Falcone, Hugh Dickinson, G. H. Gillanders, Karlen Shahinyan, David Kieda, Y. Khassen, T. B. Humensky, J. V. Tucci, Matteo Cerruti, N. W. Todd, Amy Furniss, G. H. Sembroski, D. S. Hanna, F. Krennrich, Daniel Nieto, A. Popkow, T. J. Pearson, Gernot Maier, J. L. Richards, Christopher S. Kochanek, T. Aune, Moritz Hütten, Wei Cui, John L. Quinn, B. Zitzer, P. Kaaret, J. V. Cardenzana, P. T. Reynolds, Walter Max-Moerbeck, Julien Rousselle, Manel Errando, S. Kumar, S. P. Wakely, C. A. Johnson, J. L. Prieto, Sinéad M. Griffin, Jonathan Biteau, Andrew J. Drake, J. P. Finley, J. P. Dumm, S. Vincent, A. W. Smith, J. D. Eisch, A. Weinstein, Gordon T. Richards, E. Roache, V. Bugaev, K. Z. Stanek, Nahee Park, Anushka Udara Abeysekara, Anna Barnacka, A. N. Otte, I. Telezhinsky, Jamie Holder, David A. Williams, D. Staszak, and ~
Subjects: extragalactic background light, Active galactic nucleus, Cosmology and Nongalactic Astrophysics (astro-ph.CO), spectra, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, telescope, Astrophysical jet, gamma rays: galaxies, emission, complete sample, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Supermassive black hole, variability, Gamma ray, Astronomy and Astrophysics, Quasar, radiation mechanisms: non-thermal, Galaxy, diffuse radiation, radiation, Extragalactic background light, mission, Space and Planetary Science, cosmology: observations, ddc:520, Astrophysics - High Energy Astrophysical Phenomena, Schwarzschild radius, absorption, fermi blazars, quasars: individual (pks 1441+25-ver j1443+250), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The astrophysical journal / 2 815(2), L22 -(2015). doi:10.1088/2041-8205/815/2/L22, Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints on the diffuse radiation fields that fill the universe. The detection of significant emission above 100 GeV from a distant quasar would show that some of the radiated gamma-rays escape pair-production interactions with low-energy photons, be it the extragalactic background light (EBL), or the radiation near the supermassive black hole lying at the jet's base. VERITAS detected gamma-ray emission up to ~200 GeV from PKS 1441+25 (z = 0.939) during 2015 April, a period of high activity across all wavelengths. This observation of PKS 1441+25 suggests that the emission region is located thousands of Schwarzschild radii away from the black hole. The gamma-ray detection also sets a stringent upper limit on the near-ultraviolet to near-infrared EBL intensity, suggesting that galaxy surveys have resolved most, if not all, of the sources of the EBL at these wavelengths., Published by Institute of Physics Publ., London
Published: 2015
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41. Erratum: VERITAS deep observations of the dwarf spheroidal galaxy Segue 1 [Phys. Rev. D85, 062001 (2012)]

Author: M. P. Connolly, D. Staszak, K. Ragan, R. Dickherber, S. Thibadeau, L. Ciupik, A. Varlotta, H. J. Rose, D. S. Hanna, T. C. Arlen, P. Kaaret, D. B. Saxon, E. Collins-Hughes, G. H. Sembroski, G. Hughes, Matthias Beilicke, A. McCann, A. Cesarini, M. Vivier, John L. Quinn, Francesc Ferrer, S. Archambault, Reshmi Mukherjee, K. Tsurusaki, Gernot Maier, Nahee Park, S. P. Wakely, C. Skole, A. Bouvier, Geza Gyuk, J. E. Ward, R. A. Ong, Thomas Weisgarber, Daniel Gall, E. Aliu, Matthew R. Orr, David Kieda, K. L. Byrum, Jodi Christiansen, J. S. Perkins, S. M. Bradbury, G. Tešić, David A. Williams, Lucy Fortson, A. Cannon, Pratik Majumdar, V. V. Vassiliev, T. Aune, I. Telezhinsky, Jamie Holder, S. Godambe, J. P. Dumm, J. Ruppel, Q. Feng, L. C. Reyes, Henric Krawczynski, Amy Furniss, A. J.R. Weinstein, T. B. Humensky, M. Schroedter, Wei Cui, S. McArthur, V. Bugaev, Wystan Benbow, F. Krennrich, G. Finnegan, A. W. Smith, M. Theiling, A. S Madhavan, A. D. Falcone, E. Roache, G. D. Şentürk, H. Huan, J. H. Buckley, P. Moriarty, Nicola Galante, J. Grube, R. G. Wagner, N. Karlsson, Sinéad M. Griffin, Y. Khassen, G. Decerprit, S. Vincent, M. Kertzman, A. N. Otte, P. T. Reynolds, B. Zitzer, Manel Errando, J. P. Finley, T. C. Weekes, M. Pohl, K. Lee, and H. Prokoph
Subjects: Physics, Gravitation, Nuclear and High Energy Physics, Dark matter, Gamma ray, Astronomy, Astrophysics, Segue, Cosmology, Dwarf galaxy, Dwarf spheroidal galaxy
Published: 2015
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42. The most powerful flaring activity from the NLSy1 PMN J0948+0022

Author: V. Bugaev, D. Staszak, J. P. Finley, Daniel Nieto, K. Ragan, T. B. Humensky, Josefin Larsson, Reshmi Mukherjee, K. Meagher, Talvikki Hovatta, G. H. Sembroski, L. Ciupik, P. Fortin, Abraham D. Falcone, J. V. Tucci, Gernot Maier, B. Zitzer, Ralph Bird, J. Tyler, Wystan Benbow, J. Grube, Manel Errando, S. Kumar, R. A. Ong, C. M. Raiteri, S. P. Wakely, S. T. Griffiths, Filippo D'Ammando, J. D. Eisch, K. Berger, Julien Rousselle, Hugh Dickinson, A. Weinstein, M. J. Lang, P. Kar, David A. Williams, John L. Quinn, N. Håkansson, Henrike Fleischhack, A. Varlotta, A. N. Otte, A. O'Faolain de Bhroithe, A. W. Smith, A. McCann, A. Popkow, Geza Gyuk, I. Telezhinsky, G. H. Gillanders, Gordon T. Richards, E. Roache, Jamie Holder, F. Krennrich, Marcos Santander, Matteo Cerruti, Walter Max-Moerbeck, Anthony C. S. Readhead, H. Prokoph, J. S. Perkins, David Kieda, J. V. Cardenzana, M. Pohl, Amy Furniss, L. Gérard, P. Moriarty, Matthias Beilicke, Lucy Fortson, M. Kertzman, J. L. Richards, Xuhui Chen, Y. Khassen, Vladimir Vassiliev, M. Orienti, E. Pueschel, P. T. Reynolds, Justin D. Finke, R. Welsing, Aalto-yliopisto, Aalto University, D'Ammando, F., Orienti, M., Finke, J., Raiteri, C. M., Hovatta, T., Larsson, J., Max-Moerbeck, W., Perkins, J., Readhead, A. C. S., Richards, J. L., Beilicke, M., Benbow, W., Berger, K., Bird, R., Bugaev, V., Cardenzana, J. V., Cerruti, M., Chen, X., Ciupik, L., Dickinson, H. J., Eisch, J. D., Errando, M., Falcone, A., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Gerard, L., Gillanders, G. H., Griffiths, S. T., Grube, J., Gyuk, G., Håkansson, N., Holder, J., Humensky, T. B., Kar, P., Kertzman, M., Khassen, Y., Kieda, D., Krennrich, F., Kumar, S., Lang, M. J., Maier, G., Mccann, A., Meagher, K., Moriarty, P., Mukherjee, R., Nieto, D., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Pohl, M., Popkow, A., Prokoph, H., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rousselle, J., Santander, M., Sembroski, G. H., Smith, A. W., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Varlotta, A., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Welsing, R., Williams, D. A., and Zitzer, B.
Subjects: extragalactic background light, multiwavelength observations, Active galactic nucleus, spectrum radio quasars, individual: PMN J0948+0022 [galaxies], Astrophysics::High Energy Astrophysical Phenomena, galaxies: active, nuclei [galaxies], FOS: Physical sciences, galaxies: active, galaxies: individual: PMN J0948+0022, galaxies: nuclei, galaxies: Seyfert, gamma-rays: general, Owens Valley Radio Observatory, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 7. Clean energy, galaxies: active-galaxies: individual: pmn j0948+0022, line seyfert 1, Luminosity, law.invention, Telescope, law, Seyfert [galaxies], quasar pks 1510-089, relativistic jets, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, galactic nuclei, ta115, ta213, galaxies: individual: PMN J0948+0022, Astronomy, Astronomy and Astrophysics, gamma-rays: general, gamma-ray emission, galaxies: Seyfert, large-area telescope, x-ray, 13. Climate action, Space and Planetary Science, active [galaxies], ddc:520, Spectral energy distribution, galaxies: nuclei, Astrophysics - High Energy Astrophysical Phenomena, Radio astronomy, Flare, Fermi Gamma-ray Space Telescope, general [gamma-rays]
Abstract: Monthly notices of the Royal Astronomical Society 446(3), 2456 - 2467 (2015). doi:10.1093/mnras/stu2251, We report on multifrequency observations performed during 2012 December–2013 August of the first narrow-line Seyfert 1 galaxy detected in $\gamma$-rays, PMN J0948+0022 (z = 0.5846). A γ-ray flare was observed by the Large Area Telescope on board Fermi during 2012 December–2013 January, reaching a daily peak flux in the 0.1–100 GeV energy range of (155 $\pm$ 31) × $10^{−8}$ ph $cm^{−2} s^{−1}$ on 2013 January 1, corresponding to an apparent isotropic luminosity of $\sim$ 1.5 × $10^{48}$ erg $s^{−1}$. The $\gamma$-ray flaring period triggered Swift and Very Energetic Radiation Imaging Telescope Array System (VERITAS) observations in addition to radio and optical monitoring by Owens Valley Radio Observatory, Monitoring Of Jets in Active galactic nuclei with VLBA Experiments, and Catalina Real-time Transient Survey. A strong flare was observed in optical, UV, and X-rays on 2012 December 30, quasi-simultaneously to the $\gamma$-ray flare, reaching a record flux for this source from optical to $\gamma$-rays. VERITAS observations at very high energy (E > 100 GeV) during 2013 January 6–17 resulted in an upper limit of $F_{>0.2 TeV}$ < 4.0 × $10^{−12} ph cm^{−2} s^{−1}$. We compared the spectral energy distribution (SED) of the flaring state in 2013 January with that of an intermediate state observed in 2011. The two SEDs, modelled as synchrotron emission and an external Compton scattering of seed photons from a dust torus, can be modelled by changing both the electron distribution parameters and the magnetic field., Published by Oxford Univ. Press, Oxford
Published: 2015
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43. Discovery of Very-high-energy Emission from RGB J2243+203 and Derivation of Its Redshift Upper Limit

Author: D. Staszak, Daniel Nieto, M. J. Lang, Marcos Santander, Moritz Hütten, M. P. Connolly, Anushka Udara Abeysekara, M. Buchovecky, N. Kelley-Hoskins, Sinéad M. Griffin, David A. Williams, John L. Quinn, P. Moriarty, R. A. Ong, Q. Feng, Ralph Bird, J. Grube, I. Telezhinsky, Wystan Benbow, M. Kertzman, Lucy Fortson, Maria Krause, M. Poh, P. Wilcox, E. Roache, A. Archer, P. T. Reynolds, Gordon T. Richards, A. N. Otte, J. Tyler, J. H. Buckley, F. Krennrich, Jamie Holder, A. Wilhelm, S. McArthur, V. Bugaev, O. Hervet, O. M. Weiner, Henrike Fleischhack, P. Kaaret, David Kieda, V. V. Vassiliev, Abraham D. Falcone, Karlen Shahinyan, A. Weinstein, J. P. Finley, Matteo Cerruti, Amy Furniss, N. H. Park, Gernot Maier, S. P. Wakely, C. A. Johnson, G. H. Gillanders, E. Puesche, B. Zitzer, K. Ragan, S. Kumar, T. B. Humensky, A. Popkow, I. Sadeh, S. Archambault, S. O'Brien, R. Mukherjee, D. S. Hanna, G. H. Sembroski, Robert Brose, C. Rulten, A. Petrashyk, P. Kar, and Wei Cui
Subjects: extragalactic background light, catalog, Photon, Astrophysics::High Energy Astrophysical Phenomena, blazars, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, telescope, 01 natural sciences, Power law, bl lacertae objects, galaxies: individual (rgb j2243+203), 0103 physical sciences, Blazar, Electronic band structure, 010303 astronomy & astrophysics, parameters, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Spectral index, 010308 nuclear & particles physics, Institut für Physik und Astronomie, Astronomy and Astrophysics, Cherenkov Telescope Array, Redshift, Space and Planetary Science, ddc:520, Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract: Very-high-energy (VHE; $>$ 100 GeV) gamma-ray emission from the blazar RGB J2243+203 was discovered with the VERITAS Cherenkov telescope array, during the period between 21 and 24 December 2014. The VERITAS energy spectrum from this source can be fit by a power law with a photon index of $4.6 \pm 0.5$, and a flux normalization at 0.15 TeV of $(6.3 \pm 1.1) \times 10^{-10} ~ \textrm{cm}^{-2} \textrm{s}^{-1} \textrm{TeV}^{-1}$. The integrated \textit{Fermi}-LAT flux from 1 GeV to 100 GeV during the VERITAS detection is $(4.1 \pm 0.8) \times 10^{\textrm{-8}} ~\textrm{cm}^{\textrm{-2}}\textrm{s}^{\textrm{-1}}$, which is an order of magnitude larger than the four-year-averaged flux in the same energy range reported in the 3FGL catalog, ($4.0 \pm 0.1 \times 10^{\textrm{-9}} ~ \textrm{cm}^{\textrm{-2}}\textrm{s}^{\textrm{-1}}$). The detection with VERITAS triggered observations in the X-ray band with the \textit{Swift}-XRT. However, due to scheduling constraints \textit{Swift}-XRT observations were performed 67 hours after the VERITAS detection, not simultaneous with the VERITAS observations. The observed X-ray energy spectrum between 2 keV and 10 keV can be fitted with a power-law with a spectral index of $2.7 \pm 0.2$, and the integrated photon flux in the same energy band is $(3.6 \pm 0.6) \times 10^{-13} ~\textrm{cm}^{-2} \textrm{s}^{-1}$. EBL model-dependent upper limits of the blazar redshift have been derived. Depending on the EBL model used, the upper limit varies in the range from z $
Published: 2017
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44. Unprecedented study of the broadband emission of Mrk 421 during flaring activity in March 2010

Author: E. Pueschel, J. Hose, Svetlana G. Jorstad, M. F. Aller, David A. Williams, G. H. Sembroski, D. Nakajima, M. Strzys, R. Welsing, A. Archer, E. Colombo, B. Biasuzzi, F. Borracci, Stefano Ansoldi, Riccardo Paoletti, I. Telezhinsky, Jamie Holder, D. Elsaesser, D. Staszak, Dario Hrupec, L. Ciupik, L. C. Reyes, G. Bonnoli, K. Ragan, M. A. Lopez, N. Galante, Hajime Takami, J. M. Paredes, P. T. Reynolds, Natalia Lewandowska, Hugh D. Aller, L. O. Takalo, G. H. Gillanders, T. Schweizer, Mosè Mariotti, Wystan Benbow, A.-K. Overkemping, D. Hadasch, Victor Stamatescu, J. Biteau, Paul S. Smith, Gordon T. Richards, Wei Cui, A. La Barbera, Sinéad M. Griffin, E. Roache, A. López-Oramas, S. Rügamer, Juan Abel Barrio, J. A. Ros, O. M. Kurtanidze, Alessandro Carosi, Ruben Lopez-Coto, X. Paredes-Fortuny, Mark Gurwell, U. Menzel, Saverio Lombardi, Calvin A. Johnson, P. Kar, M. Villata, K. Mallot, R. J. García López, Felix Spanier, M. Kertzman, A. C. S. Readhead, E. Prandini, D. Galindo, Merja Tornikoski, Yusuke Konno, Diego F. Torres, M. G. Nikolashvili, D. Eisenacher, Antonio Stamerra, K. Kodani, Givi N. Kimeridze, Julian Sitarek, Lorand A. Sigua, K. Nishijima, J. V. Tucci, A. Cesarini, M. Perri, P. Kaaret, J. Storz, D. Dominis Prester, Martin Pohl, C. M. Raiteri, Markus Garczarczyk, C. Fruck, A. Sillanpää, N. Håkansson, M. Makariev, T. Toyama, L. Maraschi, A. Pichel, Jose Miguel Miranda, Matteo Cerruti, Konstancja Satalecka, J. Becerra González, P. Antoranz, Amy Furniss, S. P. Wakely, B. Jordan, Elena G. Larionova, Xuhui Chen, H. C. Lin, Geza Gyuk, Louis Antonelli, Michele Doro, Abelardo Moralejo, Jelena Aleksić, S. McArthur, M. L. Knoetig, P. G. Prada Moroni, P. Munar-Adrover, Ivica Puljak, E. Collins-Hughes, K. Meagher, Nikola Godinovic, Benito Marcote, T. Steinbring, W. Idec, M. V. Fonseca, Pierre Colin, P. Temnikov, M. Hayashida, Patrick Vogler, J. Tyler, A. Niedzwiecki, C. Schultz, V. Scapin, J. H. Buckley, P. Moriarty, Tomislav Terzić, K. Berger, T. Sakamoto, C. Delgado Mendez, S. R. Gozzini, B. McBreen, O. Tibolla, Shan Sun, E. de Oña Wilhelmi, Ivan S. Troitsky, David Paneque, I. Snidaric, Marc Ribó, P. Da Vela, D. Hildebrand, B. Steinke, Steven N. Shore, Q. Feng, K. Frantzen, Massimo Persic, Hidetoshi Kubo, A. Boller, D. A. Morozova, A. Wilhelm, R. Reinthal, Thomas Bretz, Sofia O. Kurtanidze, Kari Nilsson, Elina Lindfors, Justin D. Finke, J. Krause, B. De Lotto, Walter Max-Moerbeck, K. Saito, Razmik Mirzoyan, U. Barres de Almeida, A. González Muñoz, V. Kadenius, Damir Lelas, N. Mankuzhiyil, J. P. Finley, J. S. Perkins, Wen Ping Chen, S. Paiano, E. Lorenz, Karl Mannheim, H. Prokoph, Hanna Kellermann, Daniel Mazin, I. Lozano, Dorota Sobczyńska, J. D. Eisch, Wolfgang Rhode, Daniela Dorner, M. Palatiello, Joseph Moody, Lucy Fortson, M. I. Martínez, M. Gaug, P. Bangale, G. De Caneva, J. Herrera, Matthias Beilicke, Koji Noda, J. Millis, Abraham D. Falcone, Francesco Dazzi, Karlen Shahinyan, Elisa Bernardini, S. Bonnefoy, Sabrina Einecke, J. Rodriguez Garcia, W. Bednarek, Fabrizio Tavecchio, Ll. Font, A. C. Sadun, Anne Lähteenmäki, Stefano Covino, M. J. Lang, A. Varlotta, Masahiro Teshima, A. McCann, Ekaterina Koptelova, A. C. Rovero, J. Kushida, D. Tescaro, Jose Luis Contreras, G. Hughes, M. Uellenbeck, Takashi Saito, Y. Hanabata, A. Popkow, Juan Cortina, V. Bugaev, David Kieda, Reiko Orito, S. Buson, J. L. Richards, Ann E. Wehrle, D. Garrido Terrats, P. Fortin, Oscar Blanch, Ralph Bird, S. Archambault, Valeri M. Larionov, V. Scalzotto, Ana Babić, Julia Thaele, E. Carmona, A. De Angelis, A. Treves, R. A. Ong, G. Maneva, R. Zanin, A. N. Otte, Adrian Biland, J. Rico, Alan P. Marscher, Universitat de Barcelona, Department of Radio Science and Engineering, Aalto-yliopisto, Aalto University, and ~
Subjects: extragalactic background light, Ciencias Físicas, spectral energy-distribution, Flux, Non-thermal / galaxies, Astrophysics, law.invention, Relativistic particle, purl.org/becyt/ford/1 [https], atmospheric cherenkov telescopes, Raigs gamma, bl lacertae objects, law, MAGIC (telescope), Active / BL Lacertae objects, astro-ph.HE, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, individual: Mrk 421 [BL Lacertae objects], education.field_of_study, gamma-ray outburst, non-thermal [radiation mechanisms], BL Lacertae objects: individual: Mrk 421, Galaxies: active, Gamma rays: galaxies, Radiation mechanisms: non-thermal, Astronomy and Astrophysics, Space and Planetary Science, Particle acceleration, NON THERMAL RADIATION, large-area telescope, active [galaxies], galaxies [gamma rays], BL LACERTAE OBJECTS, Electrónica, self-compton model, Electricidad, Astrophysics - High Energy Astrophysical Phenomena, CIENCIAS NATURALES Y EXACTAS, Flare, Astrophysics::High Energy Astrophysical Phenomena, galaxies: active, Population, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Radio telescope, radiation mechanisms: non-thermal, gamma rays: galaxies, Radiation mechanisms, BL Lacertae objects: individual, simultaneous multiwavelength observations, AGN, education, Blazar, Individual: Mrk 421 / gamma rays, tev blazars, Gamma rays, Institut für Physik und Astronomie, purl.org/becyt/ford/1.3 [https], Galaxies, Astronomía, x-ray, Galàxies actives, Active galaxies, ddc:520
Abstract: A flare from the TeV blazar Mrk 421, occurring in March 2010, was observed for 13 consecutive days from radio to very high energy (VHE, E > 100 GeV) gamma-rays with MAGIC, VERITAS, Whipple, FermiLAT, MAXI, RXTE, Swift, GASP-WEBT, and several optical and radio telescopes. We model the day-scale SEDs with one-zone and two-zone synchrotron self-Compton (SSC) models, investigate the physical parameters, and evaluate whether the observed broadband SED variability can be associated to variations in the relativistic particle population. Flux variability was remarkable in the X-ray and VHE bands while it was minor or not significant in the other bands. The one-zone SSC model can describe reasonably well the SED of each day for the 13 consecutive days. This flaring activity is also very well described by a two-zone SSC model, where one zone is responsible for the quiescent emission while the other smaller zone, which is spatially separated from the first one, contributes to the daily-variable emission occurring in X-rays and VHE gamma-rays. Both the one-zone SSC and the two-zone SSC models can describe the daily SEDs via the variation of only four or five model parameters, under the hypothesis that the variability is associated mostly to the underlying particle population. This shows that the particle acceleration and cooling mechanism producing the radiating particles could be the main one responsible for the broadband SED variations during the flaring episodes in blazars. The two-zone SSC model provides a better agreement to the observed SED at the narrow peaks of the low- and high-energy bumps during the highest activity, although the reported one-zone SSC model could be further improved by the variation of the parameters related to the emitting region itself ($\delta$, $B$ and $R$), in addition to the parameters related to the particle population., Comment: Published in A&A, 30 pages, 15 figures, 6 tables. Online-data: multi-wavelength light curves (data in Fig. 1) and broadband spectral energy distributions (the data in Figs. 6, and B1-B4) are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A22. Corresponding authors: David Paneque (dpaneque@mpp.mpg.de), Shangyu Sun (sysun@mpp.mpg.de), Hajime Takami (takami@post.kek.jp)
Published: 2014
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45. VERITAS Observations of the BL Lac Object PG 1553+113

Author: D. Staszak, K. Ragan, S. McArthur, E. Aliu, A. Varlotta, J. Tyler, I. Telezhinsky, J. H. Buckley, B. Zitzer, Jamie Holder, L. C. Reyes, A. Archer, Matteo Cerruti, Hugh Dickinson, Amy Furniss, L. Ciupik, David A. Williams, D. S. Hanna, J. Grube, Manel Errando, A. N. Otte, Karen Byrum, Martin Pohl, A. O'Faolain de Bhroithe, J. D. Eisch, Geza Gyuk, M. P. Connolly, H. Prokoph, S. Kumar, A. Weinstein, J. Dumm, J. V. Tucci, J. P. Finley, P. Moriarty, G. Hughes, A. McCann, K. Meagher, G. H. Gillanders, Jean-Francois Rajotte, S. P. Wakely, Vladimir Vassiliev, Wystan Benbow, K. Berger, N. Galante, E. Pueschel, T. B. Humensky, David Kieda, Henric Krawczynski, A. S Madhavan, N. Håkansson, Gordon T. Richards, E. Roache, Sinéad M. Griffin, Anna Barnacka, Frank Krennrich, Xuhui Chen, B. Behera, P. Kaaret, J. V. Cardenzana, Daniel Nieto, A. Wilhelm, R. A. Ong, M. Kertzman, A. Popkow, C. A. Johnson, Lucy Fortson, S. T. Griffiths, N. H. Park, J. Millis, Q. Feng, S. Federici, Matthias Beilicke, V. Bugaev, Wei Cui, T. Aune, P. T. Reynolds, G. H. Sembroski, R. Welsing, Matthew R. Orr, J. S. Perkins, Y. Khassen, P. Kar, P. Fortin, Ralph Bird, M. J. Lang, John L. Quinn, Abraham D. Falcone, Karlen Shahinyan, and ~
Subjects: extragalactic background light, spectra, Astrophysics::High Energy Astrophysical Phenomena, blazars, pg-1553+113, FOS: Physical sciences, Flux, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, telescope, 10. No inequality, Blazar, optical spectroscopy, bl lacertae objects: general, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Spectral index, model, Gamma rays, Institut für Physik und Astronomie, Astronomy and Astrophysics, gamma-rays, Redshift, radiation, Crab Nebula, Pair production, Extragalactic background light, Space and Planetary Science, ddc:520, lacertae objects, Astrophysics - High Energy Astrophysical Phenomena, BL Lac object
Abstract: We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning the years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 and 560\,GeV, is well described by a power law with a spectral index of $4.33 \pm 0.09$. The time-averaged integral flux above $200\,$GeV measured for this period was $(1.69 \pm 0.06) \times 10^{-11} \, \mathrm{ph} \, \mathrm{cm}^{-2} \, \mathrm{s}^{-1}$, corresponding to 6.9\% of the Crab Nebula flux. We also present the combined $\gamma$-ray spectrum from the Fermi Large Area Telescope and VERITAS covering an energy range from 100~MeV to 560~GeV. The data are well fit by a power law with an exponential cutoff at $\rm {101.9 \pm 3.2 \, \mathrm{GeV}} $. The origin of the cutoff could be intrinsic to PG~1553+113 or be due to the $\gamma$-ray opacity of our universe through pair production off the extragalactic background light (EBL). Given lower limits to the redshift of $\rm z \negthinspace > \negthinspace 0.395$ based on optical/UV observations of PG~1553+113, the cutoff would be dominated by EBL absorption. Conversely, the small statistical uncertainties of the VERITAS energy spectrum have allowed us to provide a robust upper limit on the redshift of PG 1553+113 of $z \negthinspace \leq \negthinspace 0.62$. A strongly-elevated mean flux of $(2.50 \pm 0.14) \times 10^{-11} \, \mathrm{ph} \, \mathrm{cm}^{-2} \, \mathrm{s}^{-1}$ (10.3\% of the Crab Nebula flux) was observed during 2012, with the daily flux reaching as high as $(4.44 \pm 0.71) \times 10^{-11} \, \mathrm{ph} \, \mathrm{cm}^{-2} \, \mathrm{s}^{-1}$ (18.3\% of the Crab Nebula flux) on MJD 56048. The light curve measured during the 2012 observing season is marginally inconsistent with a steady flux, giving a $\chi^2$ probability for a steady flux of 0.03\%., Comment: in press in ApJ, 2014
Published: 2014
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46. A Correlation Between Hard Gamma-ray Sources and Cosmic Voids Along the Line of Sight

Author: Aaron Dominguez, Paul M. Sutter, Amy Furniss, and Joel R. Primack
Subjects: Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Line-of-sight, Opacity, media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, Quasar, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Galaxy, Extragalactic background light, Space and Planetary Science, Sky, Blazar, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics, Fermi Gamma-ray Space Telescope, media_common
Abstract: We estimate the galaxy density along lines of sight to hard extragalactic gamma-ray sources by correlating source positions on the sky with a void catalog based on the Sloan Digital Sky Survey (SDSS). Extragalactic gamma-ray sources that are detected at very high energy (VHE; E>100 GeV) or have been highlighted as VHE-emitting candidates in the Fermi Large Area Telescope hard source catalog (together referred to as "VHE-like" sources) are distributed along underdense lines of sight at the 2.4 sigma level. There is also a less suggestive correlation for the Fermi hard source population (1.7 sigma). A correlation between 10-500 GeV flux and underdense fraction along the line of sight for VHE-like and Fermi hard sources is found at 2.4 sigma and 2.6 sigma, respectively. The preference for underdense sight lines is not displayed by gamma-ray emitting galaxies within the second Fermi catalog, containing sources detected above 100 MeV, or the SDSS DR7 quasar catalog. We investigate whether this marginal correlation might be a result of lower extragalactic background light (EBL) photon density within the underdense regions and find that, even in the most extreme case of a entirely underdense sight line, the EBL photon density is only 2% less than the nominal EBL density. Translating this into gamma-ray attenuation along the line of sight for a highly attenuated source with opacity tau(E,z) ~5, we estimate that the attentuation of gamma-rays decreases no more than 10%. This decrease, although non-neglible, is unable to account for the apparent hard source correlation with underdense lines of sight., Accepted by MNRAS
Published: 2014

47. Very-high energy observations of the galactic center region by veritas in 2010-2012

Author: W. Chen, J. P. Finley, A. N. Otte, M. P. Connolly, Daniel Nieto, Abraham D. Falcone, Karlen Shahinyan, Matteo Cerruti, Amy Furniss, A. Wilhelm, L. Ciupik, B. Zitzer, M. J. Lang, J. Grube, S. Kumar, Xuhui Chen, Sinéad M. Griffin, J. Tyler, A. O'Faolain de Bhroithe, E. Pueschel, J. H. Buckley, N. H. Park, R. A. Ong, M. Kertzman, John L. Quinn, P. Kaaret, J. V. Cardenzana, P. Moriarty, J. V. Tucci, Gernot Maier, C. A. Johnson, J. Biteau, S. Federici, Reshmi Mukherjee, Karen Byrum, J. D. Eisch, S. P. Wakely, A. Popkow, Ralph Bird, Martin Pohl, A. Weinstein, S. T. Griffiths, S. McArthur, J. Dumm, G. H. Sembroski, Q. Feng, J. S. Perkins, Anna Barnacka, N. Galante, A. Archer, R. Welsing, A. McCann, Wei Cui, Anna Zajczyk, David A. Williams, A. W. Smith, V. Bugaev, Gordon T. Richards, David Kieda, E. Roache, P. Kar, D. Staszak, K. Ragan, K. Meagher, Jean-Francois Rajotte, Matthias Beilicke, Lucy Fortson, K. Berger, Henric Krawczynski, I. Telezhinsky, Jamie Holder, L. C. Reyes, P. T. Reynolds, S. Vincent, Y. Khassen, Hugh Dickinson, D. S. Hanna, A. Varlotta, Wystan Benbow, G. Hughes, N. Håkansson, Henrike Fleischhack, H. Prokoph, and Geza Gyuk
Subjects: Astrophysics::High Energy Astrophysical Phenomena, galaxy: center, Dark matter, black hole physics, FOS: Physical sciences, Cosmic ray, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, molecular clouds, gamma-ray source, gamma rays: galaxies, emission, crab-nebula, Supernova remnant, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Astroparticle physics, Physics, Supermassive black hole, variability, Galactic Center, Institut für Physik und Astronomie, Astronomy, Astronomy and Astrophysics, source catalog, radiation mechanisms: non-thermal, Astrophysics - Astrophysics of Galaxies, methods: data analysis, Galaxy, dark-matter, Space and Planetary Science, astroparticle physics, Astrophysics of Galaxies (astro-ph.GA), ddc:520, High Energy Physics::Experiment, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, sgr-a-asterisk, magic telescope, discovery, Fermi Gamma-ray Space Telescope
Abstract: The Galactic center is an interesting region for high-energy (0.1-100 GeV) and very-high-energy (E > 100 GeV) gamma-ray observations. Potential sources of GeV/TeV gamma-ray emission have been suggested, e.g., the accretion of matter onto the supermassive black hole, cosmic rays from a nearby supernova remnant (e.g. SgrA East), particle acceleration in a plerion, or the annihilation of dark matter particles. The Galactic center has been detected by EGRET and by Fermi/LAT in the MeV/GeV energy band. At TeV energies, the Galactic center was detected with moderate significance by the CANGAROO and Whipple 10 m telescopes and with high significance by H.E.S.S., MAGIC, and VERITAS. We present the results from three years of VERITAS observations conducted at large zenith angles resulting in a detection of the Galactic center on the level of 18 standard deviations at energies above ~2.5TeV. The energy spectrum is derived and is found to be compatible with hadronic, leptonic and hybrid emission models discussed in the literature. Future, more detailed measurements of the high-energy cutoff and better constraints on the high-energy flux variability will help to refine and/or disentangle the individual models., 15 pages, 7 figures, accepted for publication in ApJ
Published: 2014
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48. Spatially Resolving the very high Energy Emission from MGRO J2019+37 with VERITAS

Author: I. Telezhinsky, Jamie Holder, S. Vincent, A. Popkow, L. C. Reyes, A. Bouvier, Abraham D. Falcone, Eric V. Gotthelf, Karlen Shahinyan, Sinéad M. Griffin, P. Fortin, P. Kaaret, Jean-Francois Rajotte, Ralph Bird, T. Aune, B. Behera, Daniel Nieto, J. P. Finley, Martin Pohl, C. A. Johnson, M. Kertzman, D. Staszak, D. S. Hanna, T. B. Humensky, J. Dumm, Wystan Benbow, K. Ragan, A. O'Faolain de Bhroithe, L. Ciupik, F. Krennrich, John L. Quinn, V. Bugaev, E. Aliu, R. A. Ong, Matthias Beilicke, B. Zitzer, Oleg Kargaltsev, J. V. Tucci, S. T. Griffiths, Mallory S. E. Roberts, Gernot Maier, K. Berger, J. Grube, Manel Errando, A. McCann, Q. Feng, N. Galante, Y. Khassen, H. Prokoph, Amanda Weinstein, S. McArthur, Xuhui Chen, A. N. Otte, S. P. Wakely, M. P. Connolly, Dirk Pandel, A. W. Smith, S. Federici, A. S Madhavan, David Kieda, Henrike Fleischhack, Gordon T. Richards, E. Roache, G. H. Gillanders, Reshmi Mukherjee, G. Hughes, M. J. Lang, A. Wilhelm, Matteo Cerruti, Amy Furniss, David A. Williams, Wei Cui, P. T. Reynolds, Geza Gyuk, Vikram V. Dwarkadas, J. Tyler, Lucy Fortson, P. Moriarty, N. H. Park, J. Millis, J. H. Buckley, G. H. Sembroski, and R. Welsing
Subjects: stars, Photon, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, supernovae : individual (ctb 87), galactic plane, 01 natural sciences, Spectral line, Pulsar, pulsars : individual (psr j2021+3651), Observatory, 0103 physical sciences, pulsar wind nebula, Supernova remnant, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, cygnus region, hess, 010308 nuclear & particles physics, Star formation, Institut für Physik und Astronomie, Astronomy, Astronomy and Astrophysics, gamma-ray emission, gamma rays : stars, psr j2021+3651, milagro, Supernova, 13. Climate action, Space and Planetary Science, Milagro, ddc:520, Astrophysics - High Energy Astrophysical Phenomena, discovery, associations
Abstract: We present very high energy (VHE) imaging of MGRO J2019+37 obtained with the VERITAS observatory. The bright extended ($\sim2^{\circ}$) unidentified Milagro source is located towards the rich star formation region Cygnus-X. MGRO J2019+37 is resolved into two VERITAS sources. The faint point-like source VER J2016+371 overlaps CTB 87, a filled-center remnant (SNR) with no evidence of a supernova remnant shell at the present time. Its spectrum is well fit in the $0.65 - 10$ TeV energy range by a power-law model with photon index $2.3\pm0.4$. VER J2019+368 is a bright extended ($\sim1^{\circ}$) source, that likely accounts for the bulk of the Milagro emission and is notably coincident with PSR J2021+3651 and the star formation region Sh 2-104. Its spectrum in the range $1-30$ TeV is well fit with a power-law model of photon index $1.75\pm0.3$, among the hardest values measured in the VHE band, comparable to that observed near Vela-X. We explore the unusual spectrum and morphology in the radio and X-ray bands to constrain possible emission mechanisms for this source., 9 pages, 8 figures, accepted for publication in the Astrophysical Journal
Published: 2014
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49. Reverberation Mapping of the Kepler-Field AGN KA1858+4850

Author: Jessica K. Werk, Liuyi Pei, Tyler D. Desjardins, Mark Lacy, Bruce Margon, Carla June Carroll, My L. Nguyen, Graeme H. Smith, Krista Lynne Smith, Nao Suzuki, Kinchen J. Searcy, Scott Gustafson, C. David Laney, Gabor Worseck, Alexei V. Filippenko, Daniel J. Carson, Aaron J. Barth, S. Bradley Cenko, Ori D. Fox, Rick Edelson, Weidong Li, J. Chuck Horst, David Tytler, Elinor L. Gates, Nathaniel R. Ross, David J. Sand, Michael M. Briley, Daniel P. Cohen, Antonino Cucchiara, Marcel Neeleman, J. Xavier Prochaska, Jeffrey M. Silverman, Patrick L. Kelly, Amy Furniss, Greg Aldering, Michael D. Joner, Matthew A. Malkan, Jerome J. Fang, Joseph M. Fedrow, Kelsey I. Clubb, Douglas C. Leonard, Michael D. Gregg, and Isaac Shivvers
Subjects: Physics, Active galactic nucleus, Continuum (design consultancy), Sigma, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Light curve, Astrophysics - Astrophysics of Galaxies, Galaxy, Redshift, Black hole, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Reverberation mapping
Abstract: KA1858+4850 is a narrow-line Seyfert 1 galaxy at redshift 0.078 and is among the brightest active galaxies monitored by the Kepler mission. We have carried out a reverberation mapping campaign designed to measure the broad-line region size and estimate the mass of the black hole in this galaxy. We obtained 74 epochs of spectroscopic data using the Kast Spectrograph at the Lick 3-m telescope from February to November of 2012, and obtained complementary V-band images from five other ground-based telescopes. We measured the H-beta light curve lag with respect to the V-band continuum light curve using both cross-correlation techniques (CCF) and continuum light curve variability modeling with the JAVELIN method, and found rest-frame lags of lag_CCF = 13.53 (+2.03, -2.32) days and lag_JAVELIN = 13.15 (+1.08, -1.00) days. The H-beta root-mean-square line profile has a width of sigma_line = 770 +/- 49 km/s. Combining these two results and assuming a virial scale factor of f = 5.13, we obtained a virial estimate of M_BH = 8.06 (+1.59, -1.72) x 10^6 M_sun for the mass of the central black hole and an Eddington ratio of L/L_Edd ~ 0.2. We also obtained consistent but slightly shorter emission-line lags with respect to the Kepler light curve. Thanks to the Kepler mission, the light curve of KA1858+4850 has among the highest cadences and signal-to-noise ratios ever measured for an active galactic nucleus; thus, our black hole mass measurement will serve as a reference point for relations between black hole mass and continuum variability characteristics in active galactic nuclei.
Published: 2014
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50. Test of Models of the Cosmic Infrared Background with Multiwavelength Observations of the Blazar 1ES 1218+30.4 in 2009

Author: Wystan Benbow, Daniel Nieto, A. N. Otte, M. P. Connolly, A. Bouvier, L. Ciupik, R. Dickherber, Geza Gyuk, T. Aune, P. T. Reynolds, P. Moriarty, S. McArthur, Ralph Bird, S. Federici, J. P. Finley, J. H. Buckley, Sinéad M. Griffin, Matthias Beilicke, P. Majumdar, Lucy Fortson, N. Galante, M. J. Lang, R. A. Ong, A. Varlotta, M. Kertzman, A. S Madhavan, Markus Böttcher, A. Lamerato, Q. Feng, John L. Quinn, Gordon T. Richards, E. Roache, G. D. Şentürk, Gernot Maier, D. S. Hanna, T. C. Arlen, Wei Cui, C. Gusbar, P. Roustazadeh, G. Hughes, Vladimir Vassiliev, H. Prokoph, S. P. Wakely, R. Welsing, Matthew R. Orr, V. Bugaev, C. Skole, G. H. Gillanders, Daniel Gall, P. Kaaret, Y. Khassen, E. Collins-Hughes, A. Iii. Garson, G. Tešić, Amy Furniss, Henric Krawczynski, S. Vincent, D. B. Saxon, N. H. Park, J. Millis, K. Li, J. S. Perkins, Martin Pohl, J. Dumm, G. H. Sembroski, S. Archambault, Reshmi Mukherjee, A. Weinstein, A. D. Falcone, A. McCann, A. O'Faolain de Bhroithe, David Kieda, M. Theiling, I. Telezhinsky, Jamie Holder, David A. Williams, D. Staszak, K. Ragan, B. Zitzer, J. Grube, Manel Errando, and A. Popkow
Subjects: Smithsonian institution, Astrophysics::High Energy Astrophysical Phenomena, Cosmic background radiation, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, cosmic background radiation, timing explorer, Cosmic infrared background, gamma rays: galaxies, strong flares, Blazar, bl lacertae objects: general, Diffuse radiation, Physics, gamma-ray observations, bl lacertae objects: individual (1es1218+30.4), particle-acceleration, tev blazars, Astronomy, Institut für Physik und Astronomie, Astronomy and Astrophysics, Visible radiation, galaxies: jets, veritas observations, diffuse radiation, Red shift, large-area telescope, x-ray, Space and Planetary Science, active galactic nuclei, extragalactic magnetic-fields, ddc:520
Abstract: We present the results of a multi-wavelength campaign targeting the blazar 1ES 1218+30.4 with observations with the 1.3 m McGraw-Hill optical telescope, the Rossi X-ray Timing Explorer (RXTE), the Fermi Gamma-Ray Space Telescope, and the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The RXTE and VERITAS observations were spread over a 13 day period and revealed clear evidence for flux variability, and a strong X-ray and gamma-ray flare on 2009 February 26 (MJD 54888). The campaign delivered a well-sampled broadband energy spectrum with simultaneous RXTE and VERITAS very high energy (VHE, > 100 GeV) observations, as well as contemporaneous optical and Fermi observations. The 1ES 1218+30.4 broadband energy spectrum-the first with simultaneous X-ray and VHE gamma-ray energy spectra-is of particular interest as the source is located at a high cosmological redshift for a VHE source (z = 0.182), leading to strong absorption of VHE gamma rays by photons from the optical/infrared extragalactic background light (EBL) via gamma VHE +gamma EBL -> e(+) e(-)pair-creation processes. We model the data with a one-zone synchrotron self-Compton (SSC) emission model and with the extragalactic absorption predicted by several recent EBL models. We find that the observations are consistent with the SSC scenario and all the EBL models considered in this work. We discuss observational and theoretical avenues to improve on the EBL constraints.
Published: 2014
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