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3 results on '"Steven Hämmerich"'

1. A VLBI investigation of high-energy neutrino emitter candidates

Author

Cristina Nanci, Marcello Giroletti, Monica Orienti, Giulia Migliori, Javier Moldon, Simone Garrappa, Matthias Kadler, Eduardo Ros, Sara Buson, Tao An, Miguel Perez-Torres, Filippo D’Ammando, Prashanth Mohan, Ivan Agudo, Bong W. Sohn, Alberto J. Castro-Tirado, Yingkang Zhang, Petra Benke, Florian Eppel, Andrea Gokus, Jonas Heßdoerfer, Georgios F. Paraschos, Florian Roesch, Jonas L. Sinapius, Philip Weber, Dana Kirchner, and Steven Hämmerich

Published
2023
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2. X-ray detection of a nova in the fireball phase

Author

Ole König, Jörn Wilms, Riccardo Arcodia, Thomas Dauser, Konrad Dennerl, Victor Doroshenko, Frank Haberl, Steven Hämmerich, Christian Kirsch, Ingo Kreykenbohm, Maximilian Lorenz, Adam Malyali, Andrea Merloni, Arne Rau, Thomas Rauch, Gloria Sala, Axel Schwope, Valery Suleimanov, Philipp Weber, Klaus Werner, Universitat Politècnica de Catalunya. Departament de Física, Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica, and Ministerio de Economía y Competitividad (España)

Subjects
High-energy astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Transient astrophysical phenomena, High Energy Physics - Experiment (hep-ex), Multidisciplinary, Física::Astronomia i astrofísica [Àrees temàtiques de la UPC], X-Rays, FOS: Physical sciences, Raigs X, Astrophysics - High Energy Astrophysical Phenomena, Compact astrophysical objects, High Energy Physics - Experiment
Abstract

Novae are caused by runaway thermonuclear burning in the hydrogen-rich envelopes of accreting white dwarfs, which results in the envelope to expand rapidly and to eject most of its mass. For more than 30 years, nova theory has predicted the existence of a "fireball" phase following directly the runaway fusion, which should be observable as a short, bright, and soft X-ray flash before the nova becomes visible in the optical. Here we present the unequivocal detection of an extremely bright and very soft X-ray flash of the classical Galactic nova YZ Reticuli 11 hours prior to its 9 mag optical brightening. No X-ray source was detected 4 hours before and after the event, constraining the duration of the flash to shorter than 8 hours. In agreement with theoretical predictions, the source's spectral shape is consistent with a black body of $3.27^{+0.11}_{-0.33}\times 10^5$ K ($28.2^{+0.9}_{-2.8}$ eV), or a white dwarf atmosphere, radiating at the Eddington luminosity, with a photosphere that is only slightly larger than a typical white dwarf. This detection of the expanding white dwarf photosphere before the ejection of the envelope provides the last link of the predicted photospheric lightcurve evolution and opens a new window to measure the total nova energetics., Comment: Published in Nature on 11 May 2022

Published
2022

3. 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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