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2. Contributions of the LOFAR Cosmic Ray Key Science Project to the 35th International Cosmic Ray Conference (ICRC 2017)

Author

Bonardi, A., Buitink, S., Corstanje, A., Falcke, H., Hare, B. M., H��randel, J. R., Mitra, P., Mulrey, K., Nelles, A., Rachen, J. P., Rossetto, L., Schellart, P., Scholten, O., ter Veen, S., Thoudam, S., Trinh, T. N. G., and Winchen, T.

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

Contributions of the LOFAR Cosmic Ray Key Science Project to the 35th International Cosmic Ray Conference (ICRC 2017), compendium of 8 proceedings for the ICRC 2017

Published
2017

3. A large light-mass component of cosmic rays at 10^{17} - 10^{17.5} eV from radio observations

Author

Buitink, S., Corstanje, A., Falcke, H., H��randel, J. R., Huege, T., Nelles, A., Rachen, J. P., Rossetto, L., Schellart, P ., Scholten, O., ter Veen, S., Thoudam, S., Trinh, T. N. G., Anderson, J., Asgekar, A., Avruch, I. M., Bell, M. E., Bentum, M. J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J. W., Brouw, W. N., Br��ggen, M., Butcher, H. R., Carbone, D., Ciardi, B., Conway, J. E., de Gasperin, F., de Geus, E., Deller, A., Dettmar, R. -J., van Diepen, G., Duscha, S., Eisl��ffel, J., Engels, D., Enriquez, J. E., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Griessmeier, J. M., Gunst, A. W., van Haarlem, M. P., Hassall, T. E., Heald, G., Hessels, J. W. T., Hoeft, M., Horneffer, A., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kondratiev, V. I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Loose, G. M., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J. P., Mevius, M., Mulcahy, D. D., Munk, H., Norden, M. J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V. N., Pietka, M., Pizzo, R., Polatidis, A. G., Reich, W., R��ttgering, H. J. A., Scaife, A. M. M., Schwarz, D. J., Serylak, M., Sluman, J., Smirnov, O., Stappers, B. W., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Toribio, M. C., Vermeulen, R., Vocks, C., Vogt, C., van Weeren, R. J., Wijers, R. A. M. J., Wijnholds, S. J., Wise, M. W., Wucknitz, O., Yatawatta, S., Zarka, P., and Zensus, J. A.

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), astro-ph.HE, High Energy Physics - Experiment (hep-ex), hep-ex, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
Abstract

Cosmic rays are the highest energy particles found in nature. Measurements of the mass composition of cosmic rays between 10^{17} eV and 10^{18} eV are essential to understand whether this energy range is dominated by Galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate cascades of secondary particles (air showers) in the atmosphere and their masses are inferred from measurements of the atmospheric depth of the shower maximum, Xmax, or the composition of shower particles reaching the ground. Current measurements suffer from either low precision, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique, suitable for determination of Xmax with a duty cycle of in principle nearly 100%. The radiation is generated by the separation of relativistic charged particles in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean precision of 16 g/cm^2 between 10^{17}-10^{17.5} eV. Because of the high resolution in $Xmax we can determine the mass spectrum and find a mixed composition, containing a light mass fraction of ~80%. Unless the extragalactic component becomes significant already below 10^{17.5} eV, our measurements indicate an additional Galactic component dominating at this energy range., 35 pages, 11 figures, updated version: Pierre Auger Observatory data ICRC 2015 added to Fig 2

Published
2016
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4. A large light-mass component of cosmic rays at 1017-1017.5 electronvolts from radio observations

Author

Buitink, S, Corstanje, A, Falcke, H, Hörandel, JR, Huege, T, Nelles, A, Rachen, JP, Rossetto, L, Schellart, P, Scholten, O, Ter Veen, S, Thoudam, S, Trinh, TNG, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bonafede, A, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Carbone, D, Ciardi, B, Conway, JE, De Gasperin, F, De Geus, E, Deller, A, Dettmar, RJ, Van Diepen, G, Duscha, S, Eislöffel, J, Engels, D, Enriquez, JE, Fallows, RA, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, JM, Gunst, AW, Van Haarlem, MP, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Horneffer, A, Iacobelli, M, Intema, H, Juette, E, Karastergiou, A, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Van Leeuwen, J, Loose, GM, Maat, P, Mann, G, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mevius, M, Mulcahy, DD, Munk, H, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pietka, M, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, HJA, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Steinmetz, M, Stewart, A, Swinbank, J, Tagger, M, Tang, Y, Tasse, C, Toribio, MC, Vermeulen, R, Vocks, C, Vogt, C, Van Weeren, RJ, Wijers, RAMJ, Wijnholds, SJ, and Wise, MW

Subjects
General Science & Technology, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract

© 2016 Macmillan Publishers Limited. All rights reserved. Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017-1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate air showers - cascades of secondary particles in the atmosphere - and their masses can be inferred from measurements of the atmospheric depth of the shower maximum (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground. Current measurements have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017-1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017-1017.5 electronvolt range.

Published
2015

5. Cosmic rays as probes of atmospheric electric fields

Author

Scholten, O., Trinh, G. T. N., Schellart, P., Ebert, U., Rutjes, C., Nelles, A., Buitink, S., ter Veen, S., Horandel, J., Corstanje, A., Rachen, J. P., Thoudam, S., Falcke, H., Koehn, C. C., van den Berg, A. A. M., de Vries, K. K. D., Rossetto, L., and Research unit Astroparticle Physics

Subjects
ATMOSPHERIC PROCESSES, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, 3304 Atmospheric electricity, 3324 Lightning, Astrophysics::Cosmology and Extragalactic Astrophysics, Physics::Atmospheric and Oceanic Physics
Abstract

Energetic cosmic rays impinging on the atmosphere create a particle avalanche called an extensive air shower. In the leading plasma of this shower electric currents are induced that generate radio waves which have been detected with LOFAR, a large and dense array of simple antennas primarily developed for radio-astronomy observations.LOFAR has observed air showers under fair-weather conditions as well as under atmospheric conditions where thunderstorms occur. For air showers under fair-weather conditions the intensity as well as the polarization of the radio emission can be understood rather accurately from the present models.For air showers measured under thunderstorm conditions we observe large differences in the intensity and polarization patterns from the fair weather models. We will show that the linear as well as the circular polarization of the radio waves carry clear information on the orientation of the electric fields at different heights in the thunderstorm clouds. We will show for the first time that the circular polarization of the radio waves tells about the change of orientation of the fields with altitude. We will show that from the measured data at LOFAR the thunderstorm electric fields can be reconstructed.We thus have established the measurement of radio emission from extensive air showers induced by cosmic rays as a new tool to probe the atmospheric electric fields present in thunderclouds in a non-intrusive way.

Published
2015

7. Measuring radio emission from air showers with LOFAR

Author

Schellart, P., Falcke, H., and Radboud University Nijmegen

Subjects
Astronomy, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries)
Abstract

Contains fulltext : 138600.pdf (Publisher’s version ) (Open Access) Radboud Universiteit Nijmegen, 02 maart 2015 Promotor : Falcke, H. 152 p.

Published
2015

8. Determining atmospheric electric fields from the radio footprint of cosmic-ray induced extensive air showers as measured with LOFAR

Author

Ebert, U., Trinh, G. T. N., Buitink, S., Corstanje, A., Enriquez, J. E., Falcke, H., Horandel, J., Koehn, C., Nelles, A., Rachen, J. P., Rutjes, C., Schellart, P., Scholten, O., ter Veen, S., Thoudam, S., and Research unit Astroparticle Physics

Subjects
ATMOSPHERIC PROCESSES, 0399 General or miscellaneous, Astrophysics::High Energy Astrophysical Phenomena, 3304 Atmospheric electricity, 3324 Lightning, ATMOSPHERIC COMPOSITION AND STRUCTURE
Abstract

Energetic cosmic rays impinging on the atmosphere create a particle avalanche called extensive air shower. In the leading plasma of this shower, electric currents are induced that generate the emission of radio waves which have been detected with LOFAR (www.lofar.org), an array of a large number of simple antennas primarily developed for radio-astronomy observations. Events have been collected under fair-weather conditions as well as under atmospheric conditions where thunderstorms occur. Of the 196 radio pulses detected under fair weather conditions, the intensity as well as the polarization can be reproduced rather accurately for 192 events with the standard model [1] using a superposition of a geomagnetically-induced transverse current and charge excess contributions. This indicates that the emission process is well understood. However, for most of the events measured under thunderstorm conditions as well as for 4 fair weather events we observe large differences in intensity and polarization pattern from the fair weather model. For these events it is not possible to get a good fit of the measured intensity pattern. The dominant polarization direction differs from the expected v x B orientation. We show that this difference is a consequence of atmospheric electric fields. We also show that the effects of atmospheric electric fields are understood, and that from the cosmic-ray radio footprint the atmospheric electric field can be deduced. [1] P. Schellart et al., submitted for publication, [arXiv:1406.1355].

Published
2014

9. A method for high precision reconstruction of air shower Xmax using two-dimensional radio intensity profiles

Author

Buitink, S., Corstanje, A., Enriquez, J. E., Falcke, H., H��randel, J. R., Huege, T., Nelles, A., Rachen, J. P., Schellart, P., Scholten, O., ter Veen, S., Thoudam, S., and Trinh, T. N. G.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

The mass composition of cosmic rays contains important clues about their origin. Accurate measurements are needed to resolve long-standing issues such as the transition from Galactic to extragalactic origin, and the nature of the cutoff observed at the highest energies. Composition can be studied by measuring the atmospheric depth of the shower maximum Xmax of air showers generated by high-energy cosmic rays hitting the Earth's atmosphere. We present a new method to reconstruct Xmax based on radio measurements. The radio emission mechanism of air showers is a complex process that creates an asymmetric intensity pattern on the ground. The shape of this pattern strongly depends on the longitudinal development of the shower. We reconstruct Xmax by fitting two-dimensional intensity profiles, simulated with CoREAS, to data from the LOFAR radio telescope. In the dense LOFAR core, air showers are detected by hundreds of antennas simultaneously. The simulations fit the data very well, indicating that the radiation mechanism is now well-understood. The typical uncertainty on the reconstruction of Xmax for LOFAR showers is 17 g/cm^2., 12 pages, 10 figures, submitted to Phys. Rev. D

Published
2014

10. Method for high precision reconstruction of air shower Xmax using two-dimensional radio intensity profiles

Author

Buitink, S., Corstanje, A., Enriquez Rascon, J.E., Falcke, H., Hörandel, J.R., Huege, T., Nelles, A., Rachen, J.P., Schellart, P., Scholten, O., Veen, S. ter, Thoudam, S., Trinh, T.N.G., and Research unit Astroparticle Physics

Subjects
SPECTRUM, TELESCOPE, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, Astrophysics::Cosmology and Extragalactic Astrophysics, COSMIC-RAYS, SIMULATIONS, PULSES, ENERGY, ATMOSPHERIC SHOWERS, RADIATION, EMISSION, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries)
Abstract

The mass composition of cosmic rays contains important clues about their origin. Accurate measurements are needed to resolve longstanding issues such as the transition from Galactic to extra-Galactic origin and the nature of the cutoff observed at the highest energies. Composition can be studied by measuring the atmospheric depth of the shower maximum X-max of air showers generated by high-energy cosmic rays hitting the Earth's atmosphere. We present a new method to reconstruct X-max based on radio measurements. The radio emission mechanism of air showers is a complex process that creates an asymmetric intensity pattern on the ground. The shape of this pattern strongly depends on the longitudinal development of the shower. We reconstruct X-max by fitting two-dimensional intensity profiles, simulated with CoREAS, to data from the Low Frequency Array (LOFAR) radio telescope. In the dense LOFAR core, air showers are detected by hundreds of antennas simultaneously. The simulations fit the data very well, indicating that the radiation mechanism is now well understood. The typical uncertainty on the reconstruction of X-max for LOFAR showers is 17 g/cm(2).

Published
2014

11. Status of LOFAR Data in HDF5 Format

Author

Alexov, A., Schellart, P., Veen, S. ter, Akker, M. van den, Bähren, L., Greissmeier, J.-M., Hessels, J.W.T., Mol, J.D., Renting, G.A., Swinbank, J., Wise, M., Egret, D., Lorente, N.P.F., Ballester, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Netherlands Institute for Radio Astronomy (ASTRON), Radboud university [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), P. Ballester & D. Egret & N.P.F. Lorente, and Ballester, P.

Subjects
[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], [SDU]Sciences of the Universe [physics], Astronomy, Astronomical Society of the Pacific Conference Series
Abstract

International audience; The Hierarchical Data Format, version 5 (HDF5) is a data model, library, and file format for storing and managing data. It is designed for flexible and efficient I/O and for high volume, complex data. The Low Frequency Array (LOFAR) project is solving the challenge of data size and complexity using HDF5. Most of LOFAR's standard data products will be stored using HDF5; the beam-formed time-series data and transient buffer board data have already transitioned from project-specific binary format to HDF5. We report on our effort to pave the way towards new astronomical data encapsulation using HDF5, which can be used by future ground and space projects. The LOFAR project has formed a collaboration with NRAO, the Virtual Astronomical Observatory (VAO) and the HDF Group to obtain funding for a full-time staff member to work on documenting and developing standards for astronomical data written in HDF5. We hope our effort will enhance HDF5 visibility and usage within the community, specifically for LSST, the SKA pathfinders (ASKAP, MeerKAT, MWA, LWA), and other major new radio telescopes such as EVLA, ALMA, and eMERLIN.

Published
2012

12. LOFAR: Detecting Cosmic Rays with a Radio Telescope

Author

Corstanje, A., Akker, M. van den, Bähren, L., Falcke, H., Frieswijk, W., Hörandel, J. R., Horneffer, A., James, C. W., Kelley, J. L., McFadden, R., Mevius, M., Nelles, A., Schellart, P., Scholten, O., Thoudam, S., ter Veen, S., Research unit Astroparticle Physics, and Astronomy

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, Astronomy, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

LOFAR (the Low Frequency Array), a distributed digital radio telescope with stations in the Netherlands, Germany, France, Sweden, and the United Kingdom, is designed to enable full-sky monitoring of transient radio sources. These capabilities are ideal for the detection of broadband radio pulses generated in cosmic ray air showers. The core of LOFAR consists of 24 stations within 4 square kilometers, and each station contains 96 low-band antennas and 48 high-band antennas. This dense instrumentation will allow detailed studies of the lateral distribution of the radio signal in a frequency range of 10-250 MHz. Such studies are key to understanding the various radio emission mechanisms within the air shower, as well as for determining the potential of the radio technique for primary particle identification. We present the status of the LOFAR cosmic ray program, including the station design and hardware, the triggering and filtering schemes, and our initial observations of cosmic-ray-induced radio pulses., Comment: Contribution to the 32nd International Cosmic Ray Conference (Beijing, China, 11-18 Aug. 2011); 4 pages, 4 figures

Published
2011

13. FRATs: a real-time search for Fast Radio Transients with LOFAR

Author

Ter Veen, S., Falcke, H., Fender, R., Hörandel, J. R., Clancy James, Rawlings, S., Schellart, P., Stappers, B., Wijers, R., Wise, M., Zarka, P., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astronomy, Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Proceedings of Science, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries)
Abstract

The radio sky is not steady on timescales below one second. Pulsars (including the rotating radio transients RRATs) and solar-system objects (e.g. solar flares, jupiter bursts, saturn lightning) give rise to sub-second pulses. Also in many known radiation processes coherent radiation can more easily occur at longer wavelengths, for which the size of the emitting region is comparable to the wavelength. This makes low frequency surveys ideally suited for the detection of new emission mechanisms caused by compact objects, such as white dwarfs, neutron stars and black holes. To detect as many of these Fast Radio Transients (FRATs) as possible, we are setting up a technique to detect and identify short single pulses with LOFAR in real-time, with unprecedented sensitivity in this frequency range, and excellent discrimination against terrestrial signals.

Published
2010

14. An outreach project for LOFAR and cosmic ray detection

Author

Vos, C. M., Heino Falcke, Horneffer, A., Koopman, Y., Kuijpers, J., Nigl, A., Pepping, H. J., Schellart, P., Schoonderbeek, G., and Timmermans, C.

Subjects
Astronomy, Experimental High Energy Physics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries)
Abstract

Contains fulltext : 33285.pdf (Publisher’s version ) (Open Access)

Published
2005

15. Calibration of the LOFAR low-band antennas using the Galaxy and a model of the signal chain

Author

Mulrey, K., Bonardi, A., Buitink, S., Corstanje, A., Falcke, H., Hare, B. M., Hörandel, J. R., Huege, T., Mitra, P., Nelles, A., Rachen, J. P., Rossetto, L., Schellart, P., Scholten, O., Ter Veen, S., Thoudam, S., Trinh, T. N. G., and Winchen, T.

Subjects
7. Clean energy
Abstract

Astroparticle physics 111, 1 - 11 (2019). doi:10.1016/j.astropartphys.2019.03.004, The LOw-Frequency ARray (LOFAR) is used to make precise measurements of radio emission from extensive air showers, yielding information about the primary cosmic ray. Interpreting the measured data requires an absolute and frequency-dependent calibration of the LOFAR system response. This is particularly important for spectral analyses, because the shape of the detected signal holds information about the shower development. We revisit the calibration of the LOFAR antennas in the range of 30–80 MHz. Using the Galactic emission and a detailed model of the LOFAR signal chain, we find an improved calibration that provides an absolute energy scale and allows for the study of frequency dependent features in measured signals. With the new calibration, systematic uncertainties of 13% are reached, and comparisons of the spectral shape of calibrated data with simulations show promising agreement., Published by Elsevier Science, Amsterdam [u.a.]

17. Radio detection of cosmic rays with LOFAR

Author

Hörandel, J. R., Buitink, S., Corstanje, A., Enriquez, J. E., Falcke, H., Karskens, T., Krause, M., Nelles, A., Rachen, J. P., Rossetto, L., Schellart, P., Olaf Scholten, Ter Veen, S., Thoudam, S., Trinh, T. N. G., and Research unit Astroparticle Physics

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract

When high-energy cosmic rays (ionized atomic nuclei) impinge on the atmosphere of the Earth they interact with atomic nuclei and initiate cascades of secondary particles - the extensive air showers. Many of the secondary particles in the air showers are electrons and positrons. They cause radiation in the frequency range of tens of MHz. The LOFAR radio telescope detects this radiation in the frequency range 30 to 240 MHz. LOFAR has a high antenna density and good time resolution. In turn, the properties of the radio emission are measured in detail. The properties of the shower-inducing cosmic rays are derived from the air shower measurements, namely their direction, energy, and particle type (atomic mass). The uncertainties achieved are competative to established techniques. This demonstrates that the radio technique is now a standard tool to measure extensive air showers and to study the properties of the incoming cosmic rays. The mean logarithmic mass of cosmic rays as measured with LOFAR is derived as a function of energy. In an examplary study, these data are used to show that the radio measurements of air showers are now in a state to discriminate astrophysical models of the origin of cosmic rays.

18. The cosmic-ray energy spectrum above 1016 eV measured with the LOFAR radboud air shower array

Author

Thoudam, S., Buitink, S., Corstanje, A., Enriquez, J. E., Falcke, H., Hörandel, J. R., Anna Nelles, Rachen, J. P., Rossetto, L., Schellart, P., Scholten, O., Ter Veen, S., Trinh, T. N. G., Kessel, L., and Research unit Astroparticle Physics

Subjects
Physics::Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Physics::Atmospheric and Oceanic Physics
Abstract

The LOFAR Radboud Air Shower Array (LORA) is an array of 20 plastic scintillation detectors installed in the center of the LOFAR radio telescope in the Netherlands to measure extensive air showers induced by cosmic rays in the Earth's atmosphere. The primary goals of LORA are to trigger the read-out of the LOFAR radio antennas to record radio signals from air showers, and to assist the reconstruction of air shower properties with LOFAR by providing basic air shower parameters, such as the position of the shower axis on the ground, the arrival direction and the energy of the incoming cosmic ray. In this paper, we describe the various steps involved in the energy reconstruction of air showers measured with LORA, and present the all-particle cosmicray energy spectrum above 1016 eV reconstructed for the two extreme scenarios: pure protons and iron nuclei.

19. Polarized radio emission and radio wavefront shape of extensive air showers

Author

Corstanje, A., Buitink, S., Enriquez, J. E., Falcke, H., Hörandel, J. R., Anna Nelles, Rachen, J. P., Rossetto, L., Schellart, P., Scholten, O., Ter Veen, S., Thoudam, S., Trinh, T. N. G., and Research unit Astroparticle Physics

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract

The LOFAR radio telescope located in the north of the Netherlands offers a high density of omnidirectional radio antennas. The LOFAR key science project Cosmic Rays is therefore well suited for detailed studies of the radio signal from air showers, and has been measuring since mid-2011 at primary energies in the range of 1017 to 1018 eV. We present high-precision measurements of the polarization of the radio signals, and the shape of the radio wavefront from the lateral distribution of signal arrival times. Polarization and timing of the incoming radio pulse are complementary observables to the lateral distribution of signal power. These are shown to provide additional information on the air shower geometry and on the contribution of different radio emission mechanisms, such as the geomagnetic and charge excess processes.

20. Polarized radio emission from extensive air showers measured with LOFAR

Author

Schellart, P., Buitink, S., Corstanje, A., Enriquez, J. E., Falcke, H., Hörandel, J. R., Krause, Maria, Nelles, A., Rachen, J. P., Scholten, O., Veen, S. Ter, Thoudam, S., and Trinh, T. N. G.

Subjects
13. Climate action
Abstract

Journal of cosmology and astroparticle physics 2014(10), 014 (2014). doi:10.1088/1475-7516/2014/10/014, We present LOFAR measurements of radio emission from extensive air showers. We find that this emission is strongly polarized, with a median degree of polarization of nearly 99%, and that the angle between the polarization direction of the electric field and the Lorentz force acting on the particles, depends on the observer location in the shower plane. This can be understood as a superposition of the radially polarized charge-excess emission mechanism, first proposed by Askaryan and the geomagnetic emission mechanism proposed by Kahn and Lerche. We calculate the relative strengths of both contributions, as quantified by the charge-excess fraction, for 163 individual air showers. We find that the measured charge-excess fraction is higher for air showers arriving from closer to the zenith. Furthermore, the measured charge-excess fraction also increases with increasing observer distance from the air shower symmetry axis. The measured values range from (3.3± 1.0)% for very inclined air showers at 25 m to (20.3± 1.3)% for almost vertical showers at 225 m. Both dependencies are in qualitative agreement with theoretical predictions., Published by IOP, London

21. The LOFAR radio telescope as a Cosmic Ray detector

Author

Hörandel, J. R., Buitink, S., Corstanje, A., Emilio Enriquez, J., Falcke, H., Frieswijk, W., Krause, M., Nelles, A., Satyendra Thoudam, Schellart, P., Scholten, O., Veen, S. T. E. R., and Den Akker, M.

22. Measuring air showers with the LOFAR radio telescope

Author

Nelles, A., Buitink, S., Corstanje, A., Emilio Enriquez, J., Falcke, H., Frieswijk, W., Hörandel, J. R., Krause, M., Satyendra Thoudam, Schellart, P., Scholten, O., Veen, S. T. E. R., and Den Akker, M.

24. HIGH-ENERGY COSMIC RAYS: GALACTIC OR EXTRAGALACTIC?

Author

Hörandel, J. R., Achterberg, A., Buitink, S., Corstanje, A., Falcke, H., Nelles, A., Rachen, J. P., Rossetto, L., Schellart, P., Scholten, O., Ter Veen, S., Satyendra Thoudam, Trinh, T. N. G., and Vliet, A.

25. Probing atmospheric electric fields in thunderstorms through radio emission from extensive air showers

Author

Trinh, T. N. G., Schellart, P., Buitink, S., Corstanje, A., Enriquez, J. E., Falcke, H., Hörandel, J. R., Nelles, A., Rachen, J. P., Rossetto, L., Scholten, O., Ter Veen, S., Thoudam, S., Den Berg, A. M., Ute Ebert, Rutjes, C., Multiscale Dynamics, Research unit Astroparticle Physics, and Elementary Processes in Gas Discharges

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Physics::Atmospheric and Oceanic Physics
Abstract

We present measurements of radio emission from extensive air showers taking place during thunderstorms. Their intensity and polarization patterns are different from those observed during fair-weather conditions. We introduce a simple two-layer model for atmospheric electric fields which can reproduce the main features of the intensity and polarization patterns of air shower during thunderstorms. This in turn provides a unique way to probe atmospheric electric fields.

26. A study of the radio frequency spectrum emitted by high-energy air showers with LOFAR

Author

Rossetto, L., Buitink, S., Corstanje, A., Enriquez, J. E., Falcke, H., Hörandel, J. R., Nelles, A., Jörg Paul Rachen, Schellart, P., Scholten, O., Ter Veen, S., Thoudam, S., Trinh, T. N. G., and Research unit Astroparticle Physics

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract

The LOw Frequency ARray (LOFAR) is a multipurpose radio antenna array aimed to detect radio signals in the frequency range 10 - 240 MHz, covering a large surface in Northern Europe with a higher density in the Northern Netherlands. The detection of the radio signal emitted by extensive air showers allows to reconstruct the geometry of the observed cascade. Thus, several properties of primary particles (e.g. arrival direction, mass composition) can be inferred. We describe a study of several geometrical parameters of the radio signal emitted by extensive air showers propagating in the atmosphere, and their correlation with the observed radio frequency spectrum. In order to find the best parameters that describe the correlation between primary cosmic ray information and the emitted radio signal, a preliminary study on simulated events has been done. Monte Carlo simulations of radio signals have been produced by using the CoREAS code, a plug-in of the CORSIKA particle simulation code. The final aim of this study is to find a method to infer information of primary cosmic rays in an independent way from the well-established fluorescence and surface detector techniques, in view of affirming the radio detection technique as reliable method for the study of high energy cosmic rays.

27. Radio emission from air showers measured with LOFAR

Author

Schellart, P., Nelles, A., Corstanje, A., Buitink, S., Enriquez, E., Falcke, H., Frieswijk, W., Hörandel, J. R., Krause, M., Satyendra Thoudam, Scholten, O., Ter Veen, S., and Den Akker, M.

28. First M87 Event Horizon Telescope Results. I. the Shadow of the Supermassive Black Hole

Author

Olivier Gentaz, David J. James, Hector Olivares, John E. Barrett, Alan P. Marscher, C. M. Violette Impellizzeri, Peter Oshiro, Peter Galison, Tyler Trent, Sang-Sung Lee, Arturo I. Gómez-Ruiz, Satoki Matsushita, Carsten Kramer, Scott Paine, Dimitrios Psaltis, Mareki Honma, Kazi L.J. Rygl, Shuo Zhang, Jan Wagner, Daniel P. Marrone, Ryan Chilson, Jorge A. Preciado-López, Christopher Beaudoin, Sara Issaoun, André Young, A. A. Stark, Jordy Davelaar, Hiroshi Nagai, Zhiqiang Shen, Pablo Torne, Chris Eckert, John Wardle, Ranjani Srinivasan, David M. Gale, David Ball, Alan L. Roy, Lupin C.C. Lin, Thomas Bronzwaer, Kazunori Akiyama, W. B. Everett, Li Ming Lu, Ta Shun Wei, Sheperd S. Doeleman, Shu Hao Chang, Roberto Garcia, Richard L. Plambeck, Maciek Wielgus, Iniyan Natarajan, Raquel Fraga-Encinas, Hiroaki Nishioka, Mark G. Rawlings, Tirupati K. Sridharan, Geoffrey B. Crew, Vernon Fath, Michael H. Hecht, Frederic Gueth, Jun Yi Koay, David Sánchez-Arguelles, Chih Chiang Han, Michael Kramer, Mariafelicia De Laurentis, Kuo Liu, Oliver Porth, Jae-Young Kim, Ilje Cho, Shan Shan Zhao, Hotaka Shiokawa, Martin P. McColl, Song Chu Chang, Lei Huang, William Stahm, Makoto Inoue, Svetlana G. Jorstad, Andrew Chael, Chih Cheng Chang, Thomas P. Krichbaum, Dominic W. Pesce, Chung Chen Chen, Laura Vertatschitsch, Jonathan Weintroub, Alejandro F. Sáez-Madain, Sera Markoff, Shuichiro Tsuda, Ryan Berthold, Chao-Te Li, M. C. H. Wright, Daniel R. van Rossum, J. Peñalver, Neal R. Erickson, Remo P. J. Tilanus, John E. Carlstrom, Roger Deane, Minfeng Gu, Michael Titus, Laurent Loinard, Lia Medeiros, C. Y. Kuo, Iain Coulson, Michael Janssen, Ben Prather, Katherine L. Bouman, Lucy M. Ziurys, Norbert Wex, Freek Roelofs, Feng Gao, Yau De Huang, Dan Bintley, N. W. Halverson, Benjamin R. Ryan, Nimesh A. Patel, Aaron Faber, Mansour Karami, Robert Freund, Ming-Tang Chen, K. T. Story, Gertie Geertsema, Daryl Haggard, Paul Shaw, Ronald Grosslein, S. A. Dzib, Joseph Crowley, Kuo Chang Han, Shoko Koyama, José L. Gómez, Chet Ruszczyk, David R. Smith, Michael Bremer, Daniel Michalik, James Hoge, Karl M. Menten, Juan-Carlos Algaba, Aristeidis Noutsos, William Snow, Thomas W. Folkers, Masanori Nakamura, Homin Jiang, James M. Cordes, Uwe Bach, Christopher Risacher, Rurik A. Primiani, Pierre Christian, David H. Hughes, Wen Ping Lo, Geoffrey C. Bower, James M. Moran, Ciriaco Goddi, Yi Chen, Christopher Greer, Roger J. Cappallo, Ilse van Bemmel, Andreas Eckart, Ziyan Zhu, Chi H. Nguyen, Rubén Herrero-Illana, Robert Wharton, Antonio Hernández-Gómez, Bart Ripperda, Dominique Broguiere, Pim Schellart, Mark Derome, Chih-Wei Locutus Huang, Chen Yu Yu, Kuan Yu Liu, Lijing Shao, Christiaan D. Brinkerink, Michael D. Johnson, Mark Kettenis, Michael Lindqvist, Frederick K. Baganoff, John Conway, Remi Sassella, Nathan Whitehorn, Eduardo Ros, David P. Woody, Jessica Dempsey, Gopal Narayanan, Elisabetta Liuzzo, Akihiko Hirota, D. A. Graham, Hiroki Okino, Vincent Piétu, Alexander W. Raymond, Gregory Desvignes, Anne Kathrin Baczko, Arash Roshanineshat, Kevin M. Silva, Timothy Norton, Heino Falcke, Aleksandar Popstefanija, Ken H. Young, Per Friberg, Paul Yamaguchi, Derek Kubo, E. Castillo-Domínguez, Jason W. Henning, R. Laing, Kimihiro Kimura, Rodrigo Córdova Rosado, Roman Gold, Helge Rottmann, Silke Britzen, J. Anton Zensus, Roger Brissenden, Ru-Sen Lu, Ye-Fei Yuan, F. Peter Schloerb, Stephen R. McWhirter, Joseph R. Farah, Ue-Li Pen, Yosuke Mizuno, Charles F. Gammie, Mel Rose, Harriet Parsons, Venkatessh Ramakrishnan, Philippe Raffin, Ignacio Ruiz, Mahito Sasada, Kamal Souccar, Joseph Neilsen, J. G. A. Wouterloot, Jirong Mao, Colin J. Lonsdale, Feng Yuan, Jadyn Anczarski, Lindy Blackburn, N. Phillips, Don Sousa, Ramesh Narayan, Alan R. Whitney, Paul T. P. Ho, Kyle D. Massingill, Patrick M. Koch, Taehyun Jung, Erik M. Leitch, Junhan Kim, Nicolas Pradel, Kevin A. Dudevoir, Britton Jeter, Jason SooHoo, Tomohisa Kawashima, T. M. Crawford, Mark Gurwell, A. Montaña, R. P. Eatough, Sascha Trippe, Ivan Marti-Vidal, Dirk Muders, Craig Walther, Atish Kamble, Qingwen Wu, Chunchong Ni, George Nystrom, Yusuke Kono, Ryan Keisler, Huib Jan van Langevelde, Stefan Heyminck, Kenji Toma, Do-Young Byun, Sjoerd T. Timmer, Antxon Alberdi, Hung Yi Pu, Hugo Messias, Feryal Özel, Kotaro Moriyama, John David, M. Poirier, Mislav Baloković, Fumie Tazaki, Keiichi Asada, S. Sánchez, Wu Jiang, Tomoaki Oyama, Shami Chatterjee, Des Small, Richard Lacasse, Ray Blundell, Motoki Kino, Michael A. Nowak, Jason Dexter, Walter Alef, Jinchi Hao, Zhiyuan Li, Garrett K. Keating, Christian M. Fromm, Cornelia Müller, Ching Tang Liu, Alexandra S. Rahlin, William Montgomerie, Andrei P. Lobanov, Bradford Benson, George N. Wong, Kazuhiro Hada, Sven Dornbusch, George Reiland, Boris Georgiev, Luciano Rezzolla, Jongsoo Kim, W. Boland, Ramprasad Rao, Guang-Yao Zhao, Buell T. Jannuzi, Sandra Bustamente, Daniel C. M. Palumbo, Tod R. Lauer, Karl Friedrich Schuster, Ronald Hesper, Zheng Meyer-Zhao, John Kuroda, Ramesh Karuppusamy, Pierre Martin-Cocher, Chi-kwan Chan, Timothy C. Chuter, Izumi Mizuno, Vincent L. Fish, Yutaka Hasegawa, Roberto Neri, Matthew R. Dexter, Paul Tiede, Rodrigo Amestica, S. Navarro, William T. Freeman, Callie Matulonis, Luis C. Ho, Hideo Ogawa, Shiro Ikeda, Ralph G. Marson, A. Nadolski, J. Blanchard, Ed Fomalont, Monika Moscibrodzka, Nicholas R. MacDonald, Gisela N. Ortiz-León, Bong Won Sohn, David C. Forbes, Lynn D. Matthews, Avery E. Broderick, Ziri Younsi, Tuomas Savolainen, Neil M. Nagar, Alexander Allardi, M. Mora-Klein, Yuzhu Cui, Yan-Rong Li, Koushik Chatterjee, Rebecca Azulay, M. Zeballos, Alan E. E. Rogers, Event Horizon Telescope Collaboration, T., Akiyama, K., Alberdi, A., Alef, W., Asada, K., Azulay, R., Baczko, A. -K., Ball, D., Balokovic, M., Barrett, J., Bintley, D., Blackburn, L., Boland, W., Bouman, K. L., Bower, G. C., 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., Cho, I., Christian, P., Conway, J. E., Cordes, J. M., Crew, G. B., Cui, Y., Davelaar, J., De Laurentis, M., Deane, R., Dempsey, J., Desvignes, G., Dexter, J., Doeleman, S. S., Eatough, R. P., Falcke, H., Fish, V. L., Fomalont, E., Fraga-Encinas, R., Freeman, W. T., Friberg, P., Fromm, C. M., Gomez, J. L., Galison, P., Gammie, C. F., Garcia, R., Gentaz, O., Georgiev, B., Goddi, C., Gold, R., Gu, M., Gurwell, M., Hada, K., 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., Johnson, M. D., Jorstad, S., Jung, T., Karami, M., Karuppusamy, R., Kawashima, T., Keating, G. K., Kettenis, M., Kim, J. -Y., Kim, J., Kino, M., Koay, J. Y., Koch, P. M., Koyama, S., Kramer, M., Kramer, C., Krichbaum, T. P., Kuo, C. -Y., Lauer, T. R., Lee, S. -S., Li, Y. -R., Li, Z., Lindqvist, M., Liu, K., Liuzzo, E., Lo, W. -P., Lobanov, A. P., Loinard, L., Lonsdale, C., Lu, R. -S., Macdonald, N. R., Mao, J., Markoff, S., Marrone, D. P., Marscher, A. P., Marti-Vidal, I., Matsushita, S., Matthews, L. D., Medeiros, L., Menten, K. M., Mizuno, Y., Mizuno, I., Moran, J. M., Moriyama, K., Moscibrodzka, M., Muller, C., Nagai, H., Nagar, N. M., Nakamura, M., Narayan, R., Narayanan, G., Natarajan, I., 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., Prather, B., Preciado-Lopez, J. A., Psaltis, D., Pu, H. -Y., Ramakrishnan, V., Rao, R., Rawlings, M. G., Raymond, A. W., Rezzolla, L., Ripperda, B., Roelofs, F., Rogers, A., Ros, E., Rose, M., Roshanineshat, A., Rottmann, H., Roy, A. L., Ruszczyk, C., Ryan, B. R., Rygl, K. L. J., Sanchez, S., Sanchez-Arguelles, D., Sasada, M., Savolainen, T., Schloerb, F. P., Schuster, K. -F., Shao, L., Shen, Z., Small, D., Sohn, B. W., Soohoo, J., Tazaki, F., Tiede, P., Tilanus, R. P. J., Titus, M., Toma, K., Torne, P., Trent, T., Trippe, S., Tsuda, S., Bemmel, I. V., Van Langevelde, H. J., Van Rossum, D. R., Wagner, J., Wardle, J., Weintroub, J., Wex, N., Wharton, R., Wielgus, M., Wong, G. N., Wu, Q., Young, K., Young, A., Younsi, Z., Yuan, F., Yuan, Y. -F., Zensus, J. A., Zhao, G., Zhao, S. -S., Zhu, Z., Algaba, J. -C., Allardi, A., Amestica, R., Anczarski, J., Bach, U., Baganoff, F. K., Beaudoin, C., Benson, B. A., Berthold, R., Blanchard, J. M., Blundell, R., Bustamente, S., Cappallo, R., Castillo-Dominguez, E., Chang, C. -C., Chang, S. -H., Chang, S. -C., Chen, C. -C., Chilson, R., Chuter, T. C., Rosado, R. C., Coulson, I. M., Crawford, T. M., Crowley, J., David, J., Derome, M., Dexter, M., Dornbusch, S., Dudevoir, K. A., Dzib, S. A., Eckart, A., Eckert, C., Erickson, N. R., Everett, W. B., Faber, A., Farah, J. R., Fath, V., Folkers, T. W., Forbes, D. C., Freund, R., Gomez-Ruiz, A. I., Gale, D. M., Gao, F., Geertsema, G., Graham, D. A., Greer, C. H., Grosslein, R., Gueth, F., Haggard, D., Halverson, N. W., Han, C. -C., Han, K. -C., Hao, J., Hasegawa, Y., Henning, J. W., Hernandez-Gomez, A., Herrero-Illana, R., Heyminck, S., Hirota, A., Hoge, J., Huang, Y. -D., Impellizzeri, C. M. V., Jiang, H., Kamble, A., Keisler, R., Kimura, K., Kono, Y., Kubo, D., Kuroda, J., Lacasse, R., Laing, R. A., Leitch, E. M., Li, C. -T., Lin, L. C. -C., Liu, C. -T., Liu, K. -Y., Lu, L. -M., Marson, R. G., Martin-Cocher, P. L., Massingill, K. D., Matulonis, C., Mccoll, M. P., Mcwhirter, S. R., Messias, H., Meyer-Zhao, Z., Michalik, D., Montana, A., Montgomerie, W., Mora-Klein, M., Muders, D., Nadolski, A., Navarro, S., Neilsen, J., Nguyen, C. H., Nishioka, H., Norton, T., Nowak, M. A., Nystrom, G., Ogawa, H., Oshiro, P., Parsons, H., Paine, S. N., Penalver, J., Phillips, N. M., Poirier, M., Pradel, N., Primiani, R. A., Raffin, P. A., Rahlin, A. S., Reiland, G., Risacher, C., Ruiz, I., Saez-Madain, A. F., Sassella, R., Schellart, P., Shaw, P., Silva, K. M., Shiokawa, H., Smith, D. R., Snow, W., Souccar, K., Sousa, D., Sridharan, T. K., Srinivasan, R., Stahm, W., Stark, A. A., Story, K., Timmer, S. T., Vertatschitsch, L., Walther, C., Wei, T. -S., Whitehorn, N., Whitney, A. R., Woody, D. P., Wouterloot, J. G. A., Wright, M., Yamaguchi, P., Yu, C. -Y., Zeballos, M., Zhang, S., Ziurys, L., Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Instituto de RadioAstronomía Milimétrica (IRAM), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Event Horizon Telescope, Academy of Finland, European Commission, Alexander von Humboldt Foundation, John Templeton Foundation, China Scholarship Council, Comisión Nacional de Investigación Científica y Tecnológica (Chile), Consejo Nacional de Ciencia y Tecnología (México), European Research Council, Generalitat Valenciana, Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Gordon and Betty Moore Foundation, Istituto Nazionale di Fisica Nucleare, Japanese Government, Japan Society for the Promotion of Science, Chinese Academy of Sciences, Max Planck Society, Ministry of Science and Technology (Taiwan), National Aeronautics and Space Administration (US), National Science Foundation (US), National Natural Science Foundation of China, Natural Sciences and Engineering Research Council of Canada, National Research Foundation of Korea, Netherlands Organization for Scientific Research, National Research Foundation (South Africa), Russian Science Foundation, Ministero dell'Istruzione, dell'Università e della Ricerca, Alberdi, Antxón, Gómez Fernández, J. L., Alberdi, Antxón [0000-0002-9371-1033], Gómez Fernández, J. L. [0000-0003-4190-7613], Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Anne Lähteenmäki Group, Department of Electronics and Nanoengineering, Aalto-yliopisto, Aalto University, Astronomy, High Energy Astrophys. & Astropart. Phys (API, FNWI), and Gravitation and Astroparticle Physics Amsterdam

Subjects
010504 meteorology & atmospheric sciences, individual (M87) [galaxies], Event horizon, Astronomy, black hole physics, jets [galaxies], galaxies: individual, Astrophysics, high-resolution, 7. Clean energy, 01 natural sciences, Photon sphere, General Relativity and Quantum Cosmology, accretion, sagittarius-a-asterisk, 010303 astronomy & astrophysics, galactic-center, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, radio-sources, accretion disks, Galactic Center, grmhd simulations, 3. Good health, energy-distributions, active [galaxies], Anatomy, Astrophysics - High Energy Astrophysical Phenomena, Active galactic nucleus, Astrophysics::High Energy Astrophysical Phenomena, galaxies: active, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), Astrophysics::Cosmology and Extragalactic Astrophysics, galaxies: individual: M87, galaxies: individual (M87), Cell and Developmental Biology, 0103 physical sciences, (M87), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Event Horizon Telescope, Supermassive black hole, ghz vlbi observations, faraday-rotation, Astronomy and Astrophysics, galaxies: jets, Astrophysics - Astrophysics of Galaxies, Black hole, Rotating black hole, Space and Planetary Science, gravitation, Astrophysics of Galaxies (astro-ph.GA), advection-dominated accretion, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], ionized-gas
Abstract

When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 ± 3 μas, which is circular and encompasses a central depression in brightness with a flux ratio 10:1. The emission ring is recovered using different calibration and imaging schemes, with its diameter and width remaining stable over four different observations carried out in different days. Overall, the observed image is consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity. The asymmetry in brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to the speed of light around a black hole. We compare our images to an extensive library of ray-traced general-relativistic magnetohydrodynamic simulations of black holes and derive a central mass of M = (6.5 ± 0.7) × 109 Me. Our radiowave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies and as the central engines of active galactic nuclei. They also present a new tool to explore gravity in its most extreme limit and on a mass scale that was so far not accessible.© 2019. The American Astronomical Society, The authors of this Letter thank the following organizations and programs: the Academy of Finland (projects 274477, 284495, 312496); the Advanced European Network of E-infrastructures for Astronomy with the SKA (AENEAS) project, supported by the European Commission Framework Programme Horizon 2020 Research and Innovation action under grant agreement 731016; the Alexander von Humboldt Stiftung; the Black Hole Initiative at Harvard University, through a grant (60477) from the John Templeton Foundation; the China Scholarship Council; Comisión Nacional de Investigación Científica y Tecnológica (CONICYT, Chile, via PIA ACT172033, Fondecyt 1171506, BASAL AFB170002, ALMA-conicyt 31140007); Consejo Nacional de Ciencia y Tecnología (CONACYT, Mexico, projects 104497, 275201, 279006, 281692); the Delaney Family via the Delaney Family John A. Wheeler Chair at Perimeter Institute; Dirección General de Asuntos del Personal Académico-Universidad Nacional 9 The Astrophysical Journal Letters, 875:L1 (17pp), 2019 April 10 The EHT Collaboration et al. Autónoma de México (DGAPA-UNAM, project IN112417); the European Research Council (ERC) Synergy Grant “BlackHoleCam: Imaging the Event Horizon of Black Holes” (grant 610058); the Generalitat Valenciana postdoctoral grant APOSTD/2018/177; the Gordon and Betty Moore Foundation (grants GBMF-3561, GBMF-5278); the Istituto Nazionale di Fisica Nucleare (INFN) sezione di Napoli, iniziative specifiche TEONGRAV; the International Max Planck Research School for Astronomy and Astrophysics at the Universities of Bonn and Cologne; the Jansky Fellowship program of the National Radio Astronomy Observatory (NRAO); the Japanese Government (Monbukagakusho: MEXT) Scholarship; the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for JSPS Research Fellowship (JP17J08829); JSPS Overseas Research Fellowships; the Key Research Program of Frontier Sciences, Chinese, Academy of Sciences (CAS, grants QYZDJ-SSW-SLH057, QYZDJ-SSW-SYS008); the Leverhulme Trust Early Career Research Fellowship; the Max-Planck-Gesellschaft (MPG); the Max Planck Partner Group of the MPG and the CAS; the MEXT/JSPS KAKENHI (grants 18KK0090, JP18K13594, JP18K03656, JP18H03721, 18K03709, 18H01245, 25120007); the MIT International Science and Technology Initiatives (MISTI) Funds; the Ministry of Science and Technology (MOST) of Taiwan (105-2112-M-001-025-MY3, 106-2112-M001-011, 106-2119-M-001-027, 107-2119-M-001-017, 107- 2119-M-001-020, and 107-2119-M-110-005); the National Aeronautics and Space Administration (NASA, Fermi Guest Investigator grant 80NSSC17K0649); the National Institute of Natural Sciences (NINS) of Japan; the National Key Research and Development Program of China (grant 2016YFA0400704, 2016YFA0400702); the National Science Foundation (NSF, grants AST-0096454, AST-0352953, AST-0521233, AST0705062, AST-0905844, AST-0922984, AST-1126433, AST1140030, DGE-1144085, AST-1207704, AST-1207730, AST1207752, MRI-1228509, OPP-1248097, AST-1310896, AST1312651, AST-1337663, AST-1440254, AST-1555365, AST1715061, AST-1615796, AST-1614868, AST-1716327, OISE1743747, AST-1816420); the Natural Science Foundation of China (grants 11573051, 11633006, 11650110427, 10625314, 11721303, 11725312, 11873028, 11873073, U1531245, 11473010); the Natural Sciences and Engineering Research Council of Canada (NSERC, including a Discovery Grant and the NSERC Alexander Graham Bell Canada Graduate Scholarships-Doctoral Program); the National Youth Thousand Talents Program of China; the National Research Foundation of Korea (grant 2015-R1D1A1A01056807, the Global PhD Fellowship Grant: NRF-2015H1A2A1033752, and the Korea Research Fellowship Program: NRF-2015H1D3A1066561); the Netherlands Organization for Scientific Research (NWO) VICI award (grant 639.043.513) and Spinoza Prize (SPI 78-409); the New Scientific Frontiers with Precision, Radio Interferometry Fellowship awarded by the South African Radio Astronomy Observatory (SARAO), which is a facility of the National Research Foundation (NRF), an agency of the Department of Science and Technology (DST) of South Africa; the Onsala Space Observatory (OSO) national infrastructure, for the provisioning of its facilities/observational support (OSO receives funding through the Swedish Research Council under grant 2017-00648); the Perimeter Institute for Theoretical Physics (research at Perimeter Institute is supported by the Government of Canada through the Department of Innovation, Science and Economic Development Canada and by the Province of Ontario through the Ministry of Economic Development, Job Creation and Trade); the Russian Science Foundation (grant 17-12-01029); the Spanish Ministerio de Economía y Competitividad (grants AYA2015-63939-C2-1-P, AYA2016-80889-P); the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709); the Toray Science Foundation; the US Department of Energy (USDOE) through the Los Alamos National Laboratory (operated by Triad National Security, LLC, for the National Nuclear Security Administration of the USDOE (Contract 89233218CNA000001)); the Italian Ministero dell’Istruzione Università e Ricerca through the grant Progetti Premiali 2012-iALMA (CUP C52I13000140001); the European Unionʼs Horizon 2020 research and innovation programme under grant agreement No 730562 RadioNet; ALMA North America Development Fund; Chandra TM6-17006X

Published
2019
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29. First M87 Event Horizon Telescope Results. II. Array and Instrumentation

Author

Monika Moscibrodzka, Elisabetta Liuzzo, F. Peter Schloerb, John Conway, Remi Sassella, Eduardo Ros, Kevin M. Silva, Christopher Beaudoin, Minfeng Gu, Stephen R. McWhirter, Nicholas R. MacDonald, Derek Kubo, E. Castillo-Domínguez, Iain Coulson, Katherine L. Bouman, John E. Barrett, Peter Oshiro, Peter Galison, Walter Alef, Ignacio Ruiz, N. Phillips, Gisela N. Ortiz-León, Ye-Fei Yuan, Arturo I. Gómez-Ruiz, Scott Paine, Dimitrios Psaltis, Mareki Honma, Juan-Carlos Algaba, Daniel P. Marrone, Alexandra S. Rahlin, Li Ming Lu, Iniyan Natarajan, Thomas W. Folkers, Zhiqiang Shen, Mariafelicia De Laurentis, Kuo Liu, Chao-Te Li, M. C. H. Wright, Mansour Karami, José L. Gómez, Roger J. Cappallo, Roger Deane, Lucy M. Ziurys, Yi Chen, Christopher Greer, William Montgomerie, Andrei P. Lobanov, George N. Wong, Bong Won Sohn, Huib Jan van Langevelde, Mark Gurwell, Ivan Marti-Vidal, Ilje Cho, Hotaka Shiokawa, Martin P. McColl, Makoto Inoue, Shu Hao Chang, K. T. Story, Joseph Crowley, C. M.Violette Impellizzeri, Kazuhiro Hada, Michael Kramer, Ranjani Srinivasan, David Ball, Keiichi Asada, Des Small, Hung Yi Pu, John David, Tomoaki Oyama, Svetlana G. Jorstad, Boris Georgiev, Sheperd S. Doeleman, Oliver Porth, Nathan Whitehorn, Alan L. Roy, Kazunori Akiyama, W. B. Everett, Maciek Wielgus, Don Sousa, J. Blanchard, Ray Blundell, Motoki Kino, Karl Friedrich Schuster, Ronald Hesper, Zheng Meyer-Zhao, John Kuroda, Heino Falcke, Chung Chen Chen, Carsten Kramer, Thomas P. Krichbaum, R. P. Eatough, S. Sánchez, Roberto Garcia, Jan Wagner, Ramesh Karuppusamy, Raquel Fraga-Encinas, Hiroaki Nishioka, Mark G. Rawlings, Ed Fomalont, W. Boland, Ramprasad Rao, Timothy Norton, Ching Tang Liu, James M. Cordes, Bradford Benson, Dominic W. Pesce, Yan-Rong Li, Geoffrey B. Crew, Vernon Fath, Frederic Gueth, David Sánchez-Arguelles, Roger Brissenden, Chi-kwan Chan, Timothy C. Chuter, Qingwen Wu, Chunchong Ni, Yuzhu Cui, Guang-Yao Zhao, Harriet Parsons, Ken H. Young, Paul Yamaguchi, Mahito Sasada, Daniel R. van Rossum, Yusuke Kono, Ryan Keisler, Masanori Nakamura, Patrick M. Koch, Nicolas Pradel, Ramesh Narayan, Rodrigo Córdova Rosado, Jordy Davelaar, Hiroshi Nagai, Chih Cheng Chang, Joseph R. Farah, Ben Prather, Laura Vertatschitsch, Britton Jeter, Kuo Chang Han, Shoko Koyama, William Snow, Lindy Blackburn, Erik M. Leitch, Rurik A. Primiani, Pierre Christian, Kyle D. Massingill, Shiro Ikeda, Remo P. J. Tilanus, S. A. Dzib, Charles F. Gammie, Ziyan Zhu, Ralph G. Marson, Aleksandar Popstefanija, Helge Rottmann, Chris Eckert, Lupin C.C. Lin, Michael H. Hecht, Silke Britzen, J. Anton Zensus, Christian M. Fromm, Sera Markoff, Wu Jiang, Cornelia Müller, A. Nadolski, David H. Hughes, Zhiyuan Li, Ue-Li Pen, Yosuke Mizuno, Sascha Trippe, Jinchi Hao, Gertie Geertsema, Garrett K. Keating, Lei Huang, Chi H. Nguyen, Koushik Chatterjee, Andrew Chael, Norbert Wex, Ronald Grosslein, Nimesh A. Patel, Aaron Faber, Rebecca Azulay, Stefan Heyminck, Kenji Toma, Do-Young Byun, Christopher Risacher, Wen Ping Lo, Geoffrey C. Bower, James M. Moran, Tyler Trent, Satoki Matsushita, Bart Ripperda, Dominique Broguiere, Antxon Alberdi, Kazi L.J. Rygl, Chet Ruszczyk, T. K. Sridharan, Antony A. Stark, Michael Bremer, James Hoge, M. Zeballos, Kamal Souccar, Paul T. P. Ho, Atish Kamble, Ciriaco Goddi, Feng Gao, Yau De Huang, Dan Bintley, Alan E. E. Rogers, Ryan Chilson, Jorge A. Preciado-López, A. Montaña, Hector Olivares, Mark Derome, Michael Janssen, Robert Freund, Thomas Bronzwaer, Jun Yi Koay, Kevin A. Dudevoir, Roberto Neri, Buell T. Jannuzi, Sandra Bustamente, Mislav Baloković, S. Navarro, Shami Chatterjee, Tod R. Lauer, Alejandro F. Sáez-Madain, Sjoerd T. Timmer, Chih Chiang Han, John E. Carlstrom, Luis C. Ho, Hugo Messias, Feryal Özel, Shuichiro Tsuda, Ryan Berthold, Taehyun Jung, Akihiko Hirota, Richard Lacasse, D. A. Graham, Vincent Piétu, Homin Jiang, Shan Shan Zhao, Lia Medeiros, Song Chu Chang, Jae-Young Kim, Hideo Ogawa, Sara Issaoun, Kotaro Moriyama, Stephen Padin, Roman Gold, N. W. Halverson, Venkatessh Ramakrishnan, C. Y. Kuo, Benjamin R. Ryan, Jason Dexter, Paul Shaw, Alan R. Whitney, Karl M. Menten, Aristeidis Noutsos, Kimihiro Kimura, Mark Kettenis, Ming-Tang Chen, Jonathan Weintroub, Neal R. Erickson, Chen Yu Yu, David R. Smith, André Young, Luciano Rezzolla, Jongsoo Kim, M. Poirier, Robert Wharton, Daniel C. M. Palumbo, Pierre Martin-Cocher, Hiroki Okino, Yutaka Hasegawa, Kuan Yu Liu, David P. Woody, Sven Dornbusch, George Reiland, Arash Roshanineshat, Pablo Torne, Daniel Michalik, John Wardle, David M. Gale, Ta Shun Wei, Uwe Bach, Ilse van Bemmel, Izumi Mizuno, Vincent L. Fish, Antonio Hernández-Gómez, Matthew R. Dexter, Paul Tiede, Rodrigo Amestica, Pim Schellart, Michael D. Johnson, Mel Rose, Callie Matulonis, J. G. A. Wouterloot, Jason SooHoo, Tomohisa Kawashima, T. M. Crawford, Dirk Muders, Craig Walther, Richard L. Plambeck, William Stahm, George Nystrom, David C. Forbes, Lynn D. Matthews, Avery E. Broderick, Ziri Younsi, Tuomas Savolainen, Neil M. Nagar, Alexander Allardi, M. Mora-Klein, Fumie Tazaki, Michael Lindqvist, Per Friberg, Olivier Gentaz, David J. James, Alan P. Marscher, Sang-Sung Lee, Chih-Wei Locutus Huang, Lijing Shao, Christiaan D. Brinkerink, Jason W. Henning, R. Laing, Feng Yuan, Junhan Kim, J. Peñalver, Michael Titus, Freek Roelofs, Laurent Loinard, Rubén Herrero-Illana, Gopal Narayanan, Alexander W. Raymond, Gregory Desvignes, Anne Kathrin Baczko, Ru-Sen Lu, Philippe Raffin, Jirong Mao, Colin J. Lonsdale, Jessica Dempsey, Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Instituto de RadioAstronomía Milimétrica (IRAM), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Event Horizon Telescope, Astronomy, Anne Lähteenmäki Group, Department of Electronics and Nanoengineering, Aalto-yliopisto, Aalto University, Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Academy of Finland, European Commission, Alexander von Humboldt Foundation, John Templeton Foundation, China Scholarship Council, Comisión Nacional de Investigación Científica y Tecnológica (Chile), Consejo Nacional de Ciencia y Tecnología (México), European Research Council, Generalitat Valenciana, Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Gordon and Betty Moore Foundation, Istituto Nazionale di Fisica Nucleare, Japanese Government, Japan Society for the Promotion of Science, Chinese Academy of Sciences, Max Planck Society, Ministry of Science and Technology (Taiwan), National Aeronautics and Space Administration (US), National Science Foundation (US), National Natural Science Foundation of China, Natural Sciences and Engineering Research Council of Canada, National Research Foundation of Korea, Netherlands Organization for Scientific Research, National Research Foundation (South Africa), Russian Science Foundation, Ministero dell'Istruzione, dell'Università e della Ricerca, Alberdi, Antxón [0000-0002-9371-1033], Gómez Fernández, J. L. [0000-0003-4190-7613], Event Horizon Telescope Collaboration, T., Akiyama, K., Alberdi, A., Alef, W., Asada, K., Azulay, R., Baczko, A. -K., Ball, D., Balokovic, M., Barrett, J., Bintley, D., Blackburn, L., Boland, W., Bouman, K. L., Bower, G. C., 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., Cho, I., Christian, P., Conway, J. E., Cordes, J. M., Crew, G. B., Cui, Y., Davelaar, J., De Laurentis, M., Deane, R., Dempsey, J., Desvignes, G., Dexter, J., Doeleman, S. S., Eatough, R. P., Falcke, H., Fish, V. L., Fomalont, E., Fraga-Encinas, R., Friberg, P., Fromm, C. M., Gomez, J. L., Galison, P., Gammie, C. F., Garcia, R., Gentaz, O., Georgiev, B., Goddi, C., Gold, R., Gu, M., Gurwell, M., Hada, K., 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., Johnson, M. D., Jorstad, S., Jung, T., Karami, M., Karuppusamy, R., Kawashima, T., Keating, G. K., Kettenis, M., Kim, J. -Y., Kim, J., Kino, M., Koay, J. Y., Koch, P. M., Koyama, S., Kramer, M., Kramer, C., Krichbaum, T. P., Kuo, C. -Y., Lauer, T. R., Lee, S. -S., Li, Y. -R., Li, Z., Lindqvist, M., Liu, K., Liuzzo, E., Lo, W. -P., Lobanov, A. P., Loinard, L., Lonsdale, C., Lu, R. -S., Macdonald, N. R., Mao, J., Markoff, S., Marrone, D. P., Marscher, A. P., Marti-Vidal, I., Matsushita, S., Matthews, L. D., Medeiros, L., Menten, K. M., Mizuno, Y., Mizuno, I., Moran, J. M., Moriyama, K., Moscibrodzka, M., Muller, C., Nagai, H., Nagar, N. M., Nakamura, M., Narayan, R., Narayanan, G., Natarajan, I., 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., Prather, B., Preciado-Lopez, J. A., Psaltis, D., Pu, H. -Y., Ramakrishnan, V., Rao, R., Rawlings, M. G., Raymond, A. W., Rezzolla, L., Ripperda, B., Roelofs, F., Rogers, A., Ros, E., Rose, M., Roshanineshat, A., Rottmann, H., Roy, A. L., Ruszczyk, C., Ryan, B. R., Rygl, K. L. J., Sanchez, S., Sanchez-Arguelles, D., Sasada, M., Savolainen, T., Schloerb, F. P., Schuster, K. -F., Shao, L., Shen, Z., Small, D., Sohn, B. W., Soohoo, J., Tazaki, F., Tiede, P., Tilanus, R. P. J., Titus, M., Toma, K., Torne, P., Trent, T., Trippe, S., Tsuda, S., Van Bemmel, I., Van Langevelde, H. J., Van Rossum, D. R., Wagner, J., Wardle, J., Weintroub, J., Wex, N., Wharton, R., Wielgus, M., Wong, G. N., Wu, Q., Young, A., Young, K., Younsi, Z., Yuan, F., Yuan, Y. -F., Zensus, J. A., Zhao, G., Zhao, S. -S., Zhu, Z., Algaba, J. -C., Allardi, A., Amestica, R., Bach, U., Beaudoin, C., Benson, B. A., Berthold, R., Blanchard, J. M., Blundell, R., Bustamente, S., Cappallo, R., Castillo-Dominguez, E., Chang, C. -C., Chang, S. -H., Chang, S. -C., Chen, C. -C., Chilson, R., Chuter, T. C., Rosado, R. C., Coulson, I. M., Crawford, T. M., Crowley, J., David, J., Derome, M., Dexter, M., Dornbusch, S., Dudevoir, K. A., Dzib, S. A., Eckert, C., Erickson, N. R., Everett, W. B., Faber, A., Farah, J. R., Fath, V., Folkers, T. W., Forbes, D. C., Freund, R., Gomez-Ruiz, A. I., Gale, D. M., Gao, F., Geertsema, G., Graham, D. A., Greer, C. H., Grosslein, R., Gueth, F., Halverson, N. W., Han, C. -C., Han, K. -C., Hao, J., Hasegawa, Y., Henning, J. W., Hernandez-Gomez, A., Herrero-Illana, R., Heyminck, S., Hirota, A., Hoge, J., Huang, Y. -D., Impellizzeri, C. M. V., Jiang, H., Kamble, A., Keisler, R., Kimura, K., Kono, Y., Kubo, D., Kuroda, J., Lacasse, R., Laing, R. A., Leitch, E. M., Li, C. -T., Lin, L. C. -C., Liu, C. -T., Liu, K. -Y., Lu, L. -M., Marson, R. G., Martin-Cocher, P. L., Massingill, K. D., Matulonis, C., Mccoll, M. P., Mcwhirter, S. R., Messias, H., Meyer-Zhao, Z., Michalik, D., Montana, A., Montgomerie, W., Mora-Klein, M., Muders, D., Nadolski, A., Navarro, S., Nguyen, C. H., Nishioka, H., Norton, T., Nystrom, G., Ogawa, H., Oshiro, P., Padin, S., Parsons, H., Paine, S. N., Penalver, J., Phillips, N. M., Poirier, M., Pradel, N., Primiani, R. A., Raffin, P. A., Rahlin, A. S., Reiland, G., Risacher, C., Ruiz, I., Saez-Madain, A. F., Sassella, R., Schellart, P., Shaw, P., Silva, K. M., Shiokawa, H., Smith, D. R., Snow, W., Souccar, K., Sousa, D., Sridharan, T. K., Srinivasan, R., Stahm, W., Stark, A. A., Story, K., Timmer, S. T., Vertatschitsch, L., Walther, C., Wei, T. -S., Whitehorn, N., Whitney, A. R., Woody, D. P., Wouterloot, J. G. A., Wright, M., Yamaguchi, P., Yu, C. -Y., Zeballos, M., Ziurys, L., Alberdi, Antxón, Gómez Fernández, J. L., High Energy Astrophys. & Astropart. Phys (API, FNWI), and Gravitation and Astroparticle Physics Amsterdam

Subjects
010504 meteorology & atmospheric sciences, individual (M87) [galaxies], Event horizon, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, interferometers [instrumentation], black hole physics, FOS: Physical sciences, galaxies: individual, General Relativity and Quantum Cosmology (gr-qc), galaxies: individual: M87, 01 natural sciences, General Relativity and Quantum Cosmology, galaxies: individual (M87), instrumentation: interferometer, 0103 physical sciences, Very-long-baseline interferometry, Angular resolution, Instrumentation (computer programming), instrumentation: interferometers, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, high angular resolution [echniques], Event Horizon Telescope, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Supermassive black hole, Galaxy: center, high angular resolution [techniques], techniques: high angular resolution, gravitational lensing: strong, Astronomy and Astrophysics, center [Galaxy], Hydrogen maser, black hole physic, Astrophysics - Astrophysics of Galaxies, echniques: high angular resolution, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), strong [gravitational lensing], Millimeter, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

The Event Horizon Telescope (EHT) is a very long baseline interferometry (VLBI) array that comprises millimeter- and submillimeter-wavelength telescopes separated by distances comparable to the diameter of the Earth. At a nominal operating wavelength of ~1.3 mm, EHT angular resolution (λ/D) is ~25 μas, which is sufficient to resolve nearby supermassive black hole candidates on spatial and temporal scales that correspond to their event horizons. With this capability, the EHT scientific goals are to probe general relativistic effects in the strong-field regime and to study accretion and relativistic jet formation near the black hole boundary. In this Letter we describe the system design of the EHT, detail the technology and instrumentation that enable observations, and provide measures of its performance. Meeting the EHT science objectives has required several key developments that have facilitated the robust extension of the VLBI technique to EHT observing wavelengths and the production of instrumentation that can be deployed on a heterogeneous array of existing telescopes and facilities. To meet sensitivity requirements, high-bandwidth digital systems were developed that process data at rates of 64 gigabit s−1, exceeding those of currently operating cm-wavelength VLBI arrays by more than an order of magnitude. Associated improvements include the development of phasing systems at array facilities, new receiver installation at several sites, and the deployment of hydrogen maser frequency standards to ensure coherent data capture across the array. These efforts led to the coordination and execution of the first Global EHT observations in 2017 April, and to event-horizon-scale imaging of the supermassive black hole candidate in M87.© 2019. The American Astronomical Society, The authors of this Letter thank the following organizations and programs: the Academy of Finland (projects 274477, 284495, 312496); the Advanced European Network of E-infrastructures for Astronomy with the SKA (AENEAS) project, supported by the European Commission Framework Programme Horizon 2020 Research and Innovation action under grant agreement 731016; the Alexander von Humboldt Stiftung; the Black Hole Initiative at Harvard University, through a grant (60477) from the John Templeton Foundation; the China Scholarship Council; Comisión Nacional de Investigación Científica y Tecnológica (CONICYT, Chile, via PIA ACT172033, Fondecyt 1171506, BASAL AFB170002, ALMA-conicyt 31140007); Consejo Nacional de Ciencia y Tecnología (CONACYT, Mexico, projects 104497, 275201, 279006, 281692); the Delaney Family via the Delaney Family John A. Wheeler Chair at Perimeter Institute; Dirección General de Asuntos del Personal Académico-Universidad Nacional 9 The Astrophysical Journal Letters, 875:L1 (17pp), 2019 April 10 The EHT Collaboration et al. Autónoma de México (DGAPA-UNAM, project IN112417); the European Research Council (ERC) Synergy Grant “BlackHoleCam: Imaging the Event Horizon of Black Holes” (grant 610058); the Generalitat Valenciana postdoctoral grant APOSTD/2018/177; the Gordon and Betty Moore Foundation (grants GBMF-3561, GBMF-5278); the Istituto Nazionale di Fisica Nucleare (INFN) sezione di Napoli, iniziative specifiche TEONGRAV; the International Max Planck Research School for Astronomy and Astrophysics at the Universities of Bonn and Cologne; the Jansky Fellowship program of the National Radio Astronomy Observatory (NRAO); the Japanese Government (Monbukagakusho: MEXT) Scholarship; the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for JSPS Research Fellowship (JP17J08829); JSPS Overseas Research Fellowships; the Key Research Program of Frontier Sciences, Chinese, Academy of Sciences (CAS, grants QYZDJ-SSW-SLH057, QYZDJ-SSW-SYS008); the Leverhulme Trust Early Career Research Fellowship; the Max-Planck-Gesellschaft (MPG); the Max Planck Partner Group of the MPG and the CAS; the MEXT/JSPS KAKENHI (grants 18KK0090, JP18K13594, JP18K03656, JP18H03721, 18K03709, 18H01245, 25120007); the MIT International Science and Technology Initiatives (MISTI) Funds; the Ministry of Science and Technology (MOST) of Taiwan (105-2112-M-001-025-MY3, 106-2112-M001-011, 106-2119-M-001-027, 107-2119-M-001-017, 107- 2119-M-001-020, and 107-2119-M-110-005); the National Aeronautics and Space Administration (NASA, Fermi Guest Investigator grant 80NSSC17K0649); the National Institute of Natural Sciences (NINS) of Japan; the National Key Research and Development Program of China (grant 2016YFA0400704, 2016YFA0400702); the National Science Foundation (NSF, grants AST-0096454, AST-0352953, AST-0521233, AST0705062, AST-0905844, AST-0922984, AST-1126433, AST1140030, DGE-1144085, AST-1207704, AST-1207730, AST1207752, MRI-1228509, OPP-1248097, AST-1310896, AST1312651, AST-1337663, AST-1440254, AST-1555365, AST1715061, AST-1615796, AST-1614868, AST-1716327, OISE1743747, AST-1816420); the Natural Science Foundation of China (grants 11573051, 11633006, 11650110427, 10625314, 11721303, 11725312, 11873028, 11873073, U1531245, 11473010); the Natural Sciences and Engineering Research Council of Canada (NSERC, including a Discovery Grant and the NSERC Alexander Graham Bell Canada Graduate Scholarships-Doctoral Program); the National Youth Thousand Talents Program of China; the National Research Foundation of Korea (grant 2015-R1D1A1A01056807, the Global PhD Fellowship Grant: NRF-2015H1A2A1033752, and the Korea Research Fellowship Program: NRF-2015H1D3A1066561); the Netherlands Organization for Scientific Research (NWO) VICI award (grant 639.043.513) and Spinoza Prize (SPI 78-409); the New Scientific Frontiers with Precision, Radio Interferometry Fellowship awarded by the South African Radio Astronomy Observatory (SARAO), which is a facility of the National Research Foundation (NRF), an agency of the Department of Science and Technology (DST) of South Africa; the Onsala Space Observatory (OSO) national infrastructure, for the provisioning of its facilities/observational support (OSO receives funding through the Swedish Research Council under grant 2017-00648); the Perimeter Institute for Theoretical Physics (research at Perimeter Institute is supported by the Government of Canada through the Department of Innovation, Science and Economic Development Canada and by the Province of Ontario through the Ministry of Economic Development, Job Creation and Trade); the Russian Science Foundation (grant 17-12-01029); the Spanish Ministerio de Economía y Competitividad (grants AYA2015-63939-C2-1-P, AYA2016-80889-P); the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709); the Toray Science Foundation; the US Department of Energy (USDOE) through the Los Alamos National Laboratory (operated by Triad National Security, LLC, for the National Nuclear Security Administration of the USDOE (Contract 89233218CNA000001)); the Italian Ministero dell’Istruzione Università e Ricerca through the grant Progetti Premiali 2012-iALMA (CUP C52I13000140001); the European Unionʼs Horizon 2020 research and innovation programme under grant agreement No 730562 RadioNet; ALMA North America Development Fund; Chandra TM6-17006X

Published
2019
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30. Probing Atmospheric Electric Fields in Thunderstorms through Radio Emission from Cosmic-Ray-Induced Air Showers

Author

A. Alexov, M. Serylak, M. A. Garrett, E. Juette, B. Ciardi, C. Tasse, C. Koehn, M. Kuniyoshi, Dominik J. Schwarz, M. C. Toribio, A. Nelles, F. Breitling, Jean-Mathias Grießmeier, John McKean, John D. Swinbank, Jochen Eislöffel, W. Reich, J. Moldon, Maaijke Mevius, Marcus Brüggen, Casper Rutjes, R. J. van Weeren, Emanuela Orrú, J. W. Broderick, A. G. Polatidis, Rebecca McFadden, D. McKay-Bukowski, E. de Geus, Heino Falcke, M. J. Norden, V. I. Kondratiev, Harvey Butcher, M. Pandey-Pommier, Philip Best, Pim Schellart, Jason W. T. Hessels, Philippe Zarka, S. Duscha, Richard Fallows, Arthur Corstanje, Matthias Steinmetz, H. Paas, Ute Ebert, G. Kuper, Olaf Scholten, H. J. A. Röttgering, Oleg Smirnov, R. Vermeulen, Annalisa Bonafede, Mark J. Bentum, Michel Tagger, Michael W. Wise, Jörg P. Rachen, Gianni Bernardi, Jörg R. Hörandel, H. A. Holties, Olaf Wucknitz, T. N. G. Trinh, J. E. Enriquez, S. ter Veen, A. W. Gunst, M. de Vos, I. M. Avruch, Laura Rossetto, James M. Anderson, Gottfried Mann, Stijn Buitink, Roberto Pizzo, Wilfred Frieswijk, Christian Vocks, Satyendra Thoudam, Anna M. M. Scaife, Matthias Hoeft, George Heald, Department of Astrophysics [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen]-Radboud University [Nijmegen], KVI Center for Advanced Radiation Technology, University of Groningen [Groningen], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), National Institute for Subatomic Physics [Amsterdam] (NIKHEF), Vrije Universiteit Brussel (VUB), Centrum Wiskunde & Informatica (CWI), Space Telescope Science Institute (STSci), GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), SRON Netherlands Institute for Space Research (SRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Institute for Astronomy [Edinburgh] (IfA), University of Edinburgh, University of Hamburg, Leibniz-Institut für Astrophysik Potsdam (AIP), Oxford Astrophysics, University of Oxford, University of Southampton, Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Thüringer Landessternwarte Tautenburg (TLS), Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], National Astronomical Observatory of Japan (NAOJ), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden, Universität Bielefeld = Bielefeld University, SKA South Africa, Ska South Africa, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, 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), NOVA, SNN and FOM as well as from NWO, VENI Grant No. 639-041-130, European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), High Energy Astrophys. & Astropart. Phys (API, FNWI), Schellart, P., Trinh, T.N.G., Buitink, S., Corstanje, A., Enriquez, J.E., Falcke, H., Hörandel, J.R., Nelles, A., Rachen, J.P., Rossetto, L., Scholten, O., Ter Veen, S., Thoudam, S., Ebert, U., Koehn, C., Rutjes, C., Alexov, A., Anderson, J.M., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J.W., Brüggen, M., Butcher, H.R., Ciardi, B., De Geus, E., De Vos, M., Duscha, S., Eislöffel, J., Fallows, R.A., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Heald, G., Hessels, J.W.T., Hoeft, M., Holties, H.A., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Mann, G., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mevius, M., Moldon, J., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scaife, A.M.M., Schwarz, D.J., Serylak, M., Smirnov, O., Steinmetz, M., Swinbank, J., Tagger, M., Tasse, C., Toribio, M.C., Van Weeren, R.J., Vermeulen, R., Vocks, C., Wise, M.W., Wucknitz, O., Zarka, P., Kapteyn Astronomical Institute, Elementary Processes in Gas Discharges, Center for Wireless Technology Eindhoven, Physics, Astronomy and Astrophysics Research Group, Elementary Particle Physics, Multiscale Dynamics, Radboud university [Nijmegen]-Radboud university [Nijmegen], Harvard University [Cambridge]-Smithsonian Institution, University of Oxford [Oxford], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Universiteit Leiden [Leiden], Fakultät für Physik, Universität Bielefeld, Universität Bielefeld, ITA, GBR, FRA, DEU, and NLD

Subjects
Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, General Physics and Astronomy, Cosmic ray, Astrophysics, Neutrino muon pion and other elementary particles, Physics and Astronomy (all), cosmic rays, IR-99169, Atmospheric electricity lightning, Electric field, Extensive air showers, Instrumentation and Methods for Astrophysics (astro-ph.IM), METIS-315601, Physics::Atmospheric and Oceanic Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Earth and Planetary Astrophysics (astro-ph.EP), Astroparticle physics, Physics, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, EWI-26542, LOFAR, Polarization (waves), SIMULATIONS, COREAS, 13. Climate action, Experimental High Energy Physics, Thunderstorm, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, ARRAY, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

We present measurements of radio emission from cosmic ray air showers that took place during thunderstorms. The intensity and polarization patterns of these air showers are radically different from those measured during fair-weather conditions. With the use of a simple two-layer model for the atmospheric electric field, these patterns can be well reproduced by state-of-the-art simulation codes. This in turn provides a novel way to study atmospheric electric fields., 6 pages, 3 figures, accepted for publication in Physical Review Letters

Published
2015
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31. The shape of the radio wavefront of extensive air showers as measured with LOFAR

Author

J. E. Enriquez, Wilfred Frieswijk, Y. Tang, Anna M. M. Scaife, Emanuela Orrú, Gottfried Mann, M. van den Akker, H. J. A. Röttgering, Stefan J. Wijnholds, W. Reich, Mark J. Bentum, Olaf Wucknitz, Sarod Yatawatta, Heino Falcke, Frank Breitling, Chiara Ferrari, D. Engels, Adam Stewart, Aris Karastergiou, Richard Fallows, Maria Krause, P. Maat, A. Horneffer, C. Toribio, Michel Tagger, M. A. Garrett, Jörg P. Rachen, Gianni Bernardi, Jörg R. Hörandel, M. J. Norden, Vishambhar Pandey, Matthias Hoeft, R. J. van Weeren, Jochen Eislöffel, V. I. Kondratiev, D. McKay-Bukowski, Marco Iacobelli, F. de Gasperin, A. Alexov, J.-M. Grießmeier, Maaijke Mevius, T. N. G. Trinh, G. Kuper, A. G. Polatidis, Arthur Corstanje, A. Nelles, E. Juette, I. M. Avruch, Roberto Pizzo, Olaf Scholten, Oleg Smirnov, J. Kohler, H. Paas, Satyendra Thoudam, M. de Vos, Dominik J. Schwarz, Rene C. Vermeulen, P. Zarka, Annalisa Bonafede, J. P. Hamaker, Martin Bell, J. Anderson, Matthias Steinmetz, S. ter Veen, Rebecca McFadden, A. W. Gunst, Stijn Buitink, Christian Vocks, J. W. Broderick, E. de Geus, John D. Swinbank, Harvey Butcher, M. Pandey-Pommier, S. Duscha, B. Ciardi, C. Tasse, M. Kuniyoshi, H. Munk, Marcus Brüggen, Philip Best, Pim Schellart, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Extraterrestrische Physik (MPE), Leibniz-Institut für Astrophysik Potsdam (AIP), SRON Netherlands Institute for Space Research (SRON), Delft University of Technology (TU Delft), University of Edinburgh, University of Southampton, Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Department of Astrophysical Sciences [Princeton], Princeton University, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Netherlands Research School for Astronomy (NOVA), the Samenwerkingsverband Noord-Nederland (SNN) and the Foundation for Fundamental Research on Matter (FOM) as well as support from the Netherlands Organization for Scientific Research (NWO), VENI grant 639-041-130, European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), ITA, GBR, FRA, DEU, NLD, Corstanje, A., Schellart, P., Nelles, A., Buitink, S., Enriquez, J.E., Falcke, H., Frieswijk, W., Hörandel, J.R., Krause, M., Rachen, J.P., Scholten, O., Ter Veen, S., Thoudam, S., Trinh, T.N.G., Van Den Akker, M., Alexov, A., Anderson, J., Avruch, I.M., Bell, M.E., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., De Gasperin, F., De Geus, E., De Vos, M., Duscha, S., Eislöffel, J., Engels, D., Fallows, R.A., Ferrari, C., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hoeft, M., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Maat, P., Mann, G., McFadden, R., McKay-Bukowski, D., Mevius, M., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scaife, A.M.M., Schwarz, D., Smirnov, O., Stewart, A., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Toribio, C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijnholds, S.J., Wucknitz, O., Yatawatta, S., Zarka, P., Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Universiteit Leiden [Leiden], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Astronomy, Research unit Astroparticle Physics, and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Physics::Instrumentation and Detectors, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Extensive air shower, FOS: Physical sciences, Cosmic ray, Astrophysics, 01 natural sciences, Radio telescope, Optics, 0103 physical sciences, Extensive air showers, Ultra-high-energy cosmic ray, Radio emission, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Cosmic rays, Wavefront, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, business.industry, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Air shower, Wavefront shape, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Hyperboloid, business, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Shape analysis (digital geometry)
Abstract

Extensive air showers, induced by high energy cosmic rays impinging on the Earth's atmosphere, produce radio emission that is measured with the LOFAR radio telescope. As the emission comes from a finite distance of a few kilometers, the incident wavefront is non-planar. A spherical, conical or hyperbolic shape of the wavefront has been proposed, but measurements of individual air showers have been inconclusive so far. For a selected high-quality sample of 161 measured extensive air showers, we have reconstructed the wavefront by measuring pulse arrival times to sub-nanosecond precision in 200 to 350 individual antennas. For each measured air shower, we have fitted a conical, spherical, and hyperboloid shape to the arrival times. The fit quality and a likelihood analysis show that a hyperboloid is the best parametrization. Using a non-planar wavefront shape gives an improved angular resolution, when reconstructing the shower arrival direction. Furthermore, a dependence of the wavefront shape on the shower geometry can be seen. This suggests that it will be possible to use a wavefront shape analysis to get an additional handle on the atmospheric depth of the shower maximum, which is sensitive to the mass of the primary particle., Accepted for publication in Astroparticle Physics

Published
2014
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32. LOFAR: The LOw-Frequency ARray

Author

M. P. van Haarlem, M. W. Wise, A. W. Gunst, G. Heald, J. P. McKean, J. W. T. Hessels, A. G. de Bruyn, R. Nijboer, J. Swinbank, R. Fallows, M. Brentjens, A. Nelles, R. Beck, H. Falcke, R. Fender, J. Hörandel, L. V. E. Koopmans, G. Mann, G. Miley, H. Röttgering, B. W. Stappers, R. A. M. J. Wijers, S. Zaroubi, M. van den Akker, A. Alexov, J. Anderson, K. Anderson, A. van Ardenne, M. Arts, A. Asgekar, I. M. Avruch, F. Batejat, L. Bähren, M. E. Bell, M. R. Bell, I. van Bemmel, P. Bennema, M. J. Bentum, G. Bernardi, P. Best, L. Bîrzan, A. Bonafede, A.-J. Boonstra, R. Braun, J. Bregman, F. Breitling, R. H. van de Brink, J. Broderick, P. C. Broekema, W. N. Brouw, M. Brüggen, H. R. Butcher, W. van Cappellen, B. Ciardi, T. Coenen, J. Conway, A. Coolen, A. Corstanje, S. Damstra, O. Davies, A. T. Deller, R.-J. Dettmar, G. van Diepen, K. Dijkstra, P. Donker, A. Doorduin, J. Dromer, M. Drost, A. van Duin, J. Eislöffel, J. van Enst, C. Ferrari, W. Frieswijk, H. Gankema, M. A. Garrett, F. de Gasperin, M. Gerbers, E. de Geus, J.-M. Grießmeier, T. Grit, P. Gruppen, J. P. Hamaker, T. Hassall, M. Hoeft, H. A. Holties, A. Horneffer, A. van der Horst, A. van Houwelingen, A. Huijgen, M. Iacobelli, H. Intema, N. Jackson, V. Jelic, A. de Jong, E. Juette, D. Kant, A. Karastergiou, A. Koers, H. Kollen, V. I. Kondratiev, E. Kooistra, Y. Koopman, A. Koster, M. Kuniyoshi, M. Kramer, G. Kuper, P. Lambropoulos, C. Law, J. van Leeuwen, J. Lemaitre, M. Loose, P. Maat, G. Macario, S. Markoff, J. Masters, R. A. McFadden, D. McKay-Bukowski, H. Meijering, H. Meulman, M. Mevius, E. Middelberg, R. Millenaar, J. C. A. Miller-Jones, R. N. Mohan, J. D. Mol, J. Morawietz, R. Morganti, D. D. Mulcahy, E. Mulder, H. Munk, L. Nieuwenhuis, R. van Nieuwpoort, J. E. Noordam, M. Norden, A. Noutsos, A. R. Offringa, H. Olofsson, A. Omar, E. Orrú, R. Overeem, H. Paas, M. Pandey-Pommier, V. N. Pandey, R. Pizzo, A. Polatidis, D. Rafferty, S. Rawlings, W. Reich, J.-P. de Reijer, J. Reitsma, G. A. Renting, P. Riemers, E. Rol, J. W. Romein, J. Roosjen, M. Ruiter, A. Scaife, K. van der Schaaf, B. Scheers, P. Schellart, A. Schoenmakers, G. Schoonderbeek, M. Serylak, A. Shulevski, J. Sluman, O. Smirnov, C. Sobey, H. Spreeuw, M. Steinmetz, C. G. M. Sterks, H.-J. Stiepel, K. Stuurwold, M. Tagger, Y. Tang, C. Tasse, I. Thomas, S. Thoudam, M. C. Toribio, B. van der Tol, O. Usov, M. van Veelen, A.-J. van der Veen, S. ter Veen, J. P. W. Verbiest, R. Vermeulen, N. Vermaas, C. Vocks, C. Vogt, M. de Vos, E. van der Wal, R. van Weeren, H. Weggemans, P. Weltevrede, S. White, S. J. Wijnholds, T. Wilhelmsson, O. Wucknitz, S. Yatawatta, P. Zarka, A. Zensus, J. van Zwieten, Netherlands Institute for Radio Astronomy (ASTRON), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Institute of Mathematical and Physical Sciences, Radboud university [Nijmegen], Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Max-Planck-Institut für Radioastronomie (MPIFR), University of Southampton, Leibniz-Institut für Astrophysik Potsdam (AIP), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Medical Center Haaglanden, SRON Netherlands Institute for Space Research (SRON), University of Edinburgh, Jacobs University [Bremen], Technische Universität Dresden = Dresden University of Technology (TU Dresden), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Department of Reproduction and Development, Erasmus University Rotterdam, London Institute for Mathematical Sciences, Netherlands Centre for Biodiversity, Leiden, The Netherlands, Thüringer Landessternwarte Tautenburg (TLS), Laboratoire Réactions et Génie des Procédés (LRGP), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Medstar Research Institute, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Plant Research International, Business Unit Bioscience, Wageningen University and Research [Wageningen] (WUR), Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Centre de Mathématiques Laurent Schwartz (CMLS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université de La Réunion (UR), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], Amsterdam Center for Multiscale Modeling, Vrije Universiteit Amsterdam [Amsterdam] (VU), Vrije Universiteit Medical Centre (VUMC), Queen's Medical Centre, National Radio Astronomy Observatory (NRAO), University of Oulu, Department of Economics, Bryant University, Center for Agricultural Research in Suriname CELOS and Department of Biology, Anton de Kom Universiteit van Suriname - Anton de Kom University of Suriname [Paramaribo] (UVS), DLR Institute of Aerospace Medicine, Deutsches Zentrum für Luft- und Raumfahrt [Köln] (DLR), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Geophysical Institute [Bergen] (GFI / BiU), University of Bergen (UiB), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, Academic Medical Center - Academisch Medisch Centrum [Amsterdam] (AMC), School of Physics and Astronomy [Southampton], Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Rhodes University, Grahamstown, Center for Information Technology CIT, Université de Groningen, Processus d'Activation Sélective par Transfert d'Energie Uni-électronique ou Radiatif (UMR 8640) (PASTEUR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Département de Chimie - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, 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), Center for Operations and Econometrics, Center of Operation Research and Econometrics [Louvain] (CORE), Université Catholique de Louvain = Catholic University of Louvain (UCL)-Université Catholique de Louvain = Catholic University of Louvain (UCL), Finca El Encin, Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario (IMIDRA), Department of Surgery (EINDHOVEN - Surgery), Catharina Hospital, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Astronomy, KVI - Center for Advanced Radiation Technology, Radboud University [Nijmegen], Universiteit Leiden, Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Harvard University-Smithsonian Institution, UMR Peuplement Végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT - INRA), Institut National de la Recherche Agronomique (INRA), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Technische Universität Dresden (TUD), university Rotterdam, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Wageningen University and Research Centre [Wageningen] (WUR), Università degli Studi di Roma 'La Sapienza' [Rome], Department of Physics, University of Crete [Heraklion] (UOC), Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas (FORTH), Anton de Kom University of Suriname, Geophysical Institute [Bergen], University of Bergen (UIB), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS), SKA South Africa, Ska South Africa, Center for Operations and Econometrics, Universit´e catholique de Louvain and Fonds National de la Recherche Scientifique, Harvard University [Cambridge]-Smithsonian Institution, Observatoire de Paris - Site de Paris (OP), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009), High Energy Astrophys. & Astropart. Phys (API, FNWI), Van Haarlem, M.P., Wise, M.W., Gunst, A.W., Heald, G., McKean, J.P., Hessels, J.W.T., De Bruyn, A.G., Nijboer, R., Swinbank, J., Fallows, R., Brentjens, M., Nelles, A., Beck, R., Falcke, H., Fender, R., Hörandel, J., Koopmans, L.V.E., Mann, G., Miley, G., Röttgering, H., Stappers, B.W., Wijers, R.A.M.J., Zaroubi, S., Van Den Akker, M., Alexov, A., Anderson, J., Anderson, K., Van Ardenne, A., Arts, M., Asgekar, A., Avruch, I.M., Batejat, F., Bähren, L., Bell, M.E., Bell, M.R., Van Bemmel, I., Bennema, P., Bentum, M.J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Boonstra, A.-J., Braun, R., Bregman, J., Breitling, F., Van De Brink, R.H., Broderick, J., Broekema, P.C., Brouw, W.N., Brüggen, M., Butcher, H.R., Van Cappellen, W., Ciardi, B., Coenen, T., Conway, J., Coolen, A., Corstanje, A., Damstra, S., Davies, O., Deller, A.T., Dettmar, R.-J., Van Diepen, G., Dijkstra, K., Donker, P., Doorduin, A., Dromer, J., Drost, M., Van Duin, A., Eislöffel, J., Van Enst, J., Ferrari, C., Frieswijk, W., Gankema, H., Garrett, M.A., De Gasperin, F., Gerbers, M., De Geus, E., Grießmeier, J.-M., Grit, T., Gruppen, P., Hamaker, J.P., Hassall, T., Hoeft, M., Holties, H.A., Horneffer, A., Van Der Horst, A., Van Houwelingen, A., Huijgen, A., Iacobelli, M., Intema, H., Jackson, N., Jelic, V., De Jong, A., Juette, E., Kant, D., Karastergiou, A., Koers, A., Kollen, H., Kondratiev, V.I., Kooistra, E., Koopman, Y., Koster, A., Kuniyoshi, M., Kramer, M., Kuper, G., Lambropoulos, P., Law, C., Van Leeuwen, J., Lemaitre, J., Loose, M., Maat, P., Macario, G., Markoff, S., Masters, J., McFadden, R.A., McKay-Bukowski, D., Meijering, H., Meulman, H., Mevius, M., Middelberg, E., Millenaar, R., Miller-Jones, J.C.A., Mohan, R.N., Mol, J.D., Morawietz, J., Morganti, R., Mulcahy, D.D., Mulder, E., Munk, H., Nieuwenhuis, L., Van Nieuwpoort, R., Noordam, J.E., Norden, M., Noutsos, A., Offringa, A.R., Olofsson, H., Omar, A., Orrú, E., Overeem, R., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A., Rafferty, D., Rawlings, S., Reich, W., De Reijer, J.-P., Reitsma, J., Renting, G.A., Riemers, P., Rol, E., Romein, J.W., Roosjen, J., Ruiter, M., Scaife, A., Van Der Schaaf, K., Scheers, B., Schellart, P., Schoenmakers, A., Schoonderbeek, G., Serylak, M., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Spreeuw, H., Steinmetz, M., Sterks, C.G.M., Stiepel, H.-J., Stuurwold, K., Tagger, M., Tang, Y., Tasse, C., Thomas, I., Thoudam, S., Toribio, M.C., Van Der Tol, B., Usov, O., Van Veelen, M., Van Der Veen, A.-J., Ter Veen, S., Verbiest, J.P.W., Vermeulen, R., Vermaas, N., Vocks, C., Vogt, C., De Vos, M., Van Der Wal, E., Van Weeren, R., Weggemans, H., Weltevrede, P., White, S., Wijnholds, S.J., Wilhelmsson, T., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., and Van Zwieten, J.

Subjects
instrumentation: interferometers -radio continuum: general -radio lines: general -dark ages, Computer science, Astronomy, INTERPLANETARY SCINTILLATION, radio continuum: general, 7. Clean energy, 01 natural sciences, Precision Array for Probing the Epoch of Reionization, law.invention, Observatory, law, first stars - telescopes, dark ages, instrumentation: interferometers, 010303 astronomy & astrophysics, Telescope, UNDERSTANDING RADIO POLARIMETRY, Instrumentation: Interferometer, SELF-CALIBRATION, Interferometry, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, reionization, Astrophysics - Instrumentation and Methods for Astrophysics, radio lines: general, first stars, Z-GREATER-THAN-5.7 QUASARS, FOS: Physical sciences, Murchison Widefield Array, 0103 physical sciences, RAY AIR-SHOWERS, Angular resolution, dark ages, reionization, first stars, Instrumentation and Methods for Astrophysics (astro-ph.IM), Remote sensing, 010308 nuclear & particles physics, telescopes, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Sextant (astronomical), Dark ages, reionization, first star, Space and Planetary Science, [SDU]Sciences of the Universe [physics], PROBE WMAP OBSERVATIONS, DIGITAL SKY SURVEY, HIGH-REDSHIFT, MONTE-CARLO SIMULATIONS, INTERGALACTIC MEDIUM
Abstract

LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR covers the largely unexplored low-frequency range from 10-240 MHz and provides a number of unique observing capabilities. Spreading out from a core located near the village of Exloo in the northeast of the Netherlands, a total of 40 LOFAR stations are nearing completion. A further five stations have been deployed throughout Germany, and one station has been built in each of France, Sweden, and the UK. Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR achieves unparalleled sensitivity and angular resolution in the low-frequency radio regime. The LOFAR facilities are jointly operated by the International LOFAR Telescope (ILT) foundation, as an observatory open to the global astronomical community. LOFAR is one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community. LOFAR's new capabilities, techniques and modus operandi make it an important pathfinder for the Square Kilometre Array (SKA). We give an overview of the LOFAR instrument, its major hardware and software components, and the core science objectives that have driven its design. In addition, we present a selection of new results from the commissioning phase of this new radio observatory., Comment: 56 pages, 34 figures, accepted for publication by A&A

Published
2013
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33. Wide-band simultaneous observations of pulsars: disentangling dispersion measure and profile variations

Author

P. Maat, Benjamin Stappers, Heino Falcke, Charlotte Sobey, Emanuela Orrú, Jason W. T. Hessels, E. Rol, L. Bähren, H. Meulman, Joris P. W. Verbiest, C. Tasse, A. Alexov, Matthias Hoeft, M. A. Garrett, Sarod Yatawatta, James Miller-Jones, Evan Keane, Michael Kramer, S. ter Veen, J. Masters, A. W. Gunst, Casey J. Law, Jochen Eislöffel, B. Scheers, Maaijke Mevius, T. E. Hassall, J. W. Broderick, R. C. Vermeulen, B. Ciardi, Martin Bell, John McKean, Luitje Koopmans, J. E. Noordam, Gerard H. Kuper, Annalisa Bonafede, Harvey Butcher, Sera Markoff, M. P. van Haarlem, E. J. Daw, Rudy Wijnands, M. Kuniyoshi, V. I. Kondratiev, M. Pandey-Pommier, A. Noutsos, K. Zagkouris, Michael R. Bell, H. Paas, J. Sluman, Michiel A. Brentjens, Ashish Asgekar, Roberto Pizzo, Marcus Brüggen, C. G. M. Sterks, W. Reich, R. A. Osten, Albert-Jan Boonstra, Michel Tagger, Stephane Corbel, A. G. Polatidis, P.G. Jonker, M. Gerbers, Stefan J. Wijnholds, J. van Leeuwen, H. Spreeuw, A. de Jong, Matthias Steinmetz, R. J. van Weeren, P. Zarka, K. Lazaridis, George Heald, Mark J. Bentum, G. M. Loose, W. N. Brouw, Patrick Weltevrede, V. S. Dhillon, Aris Karastergiou, Michael W. Wise, Gianni Bernardi, M. Serylak, Rob Fender, Ralph A. M. J. Wijers, H. J. A. Röttgering, H. A. Holties, Y. Tang, Anna M. M. Scaife, Olaf Wucknitz, H. Munk, John D. Swinbank, Jean-Mathias Griessmeier, Vishambhar Pandey, Philip Best, Pim Schellart, T. Coenen, Kenneth C. Anderson, Kapteyn Astronomical Institute, Astronomy, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), Oxford Astrophysics, University of Oxford [Oxford], Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Southampton, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), University of Sheffield [Sheffield], Thüringer Landessternwarte Tautenburg (TLS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen], Space Telescope Science Institute (STSci), School of Physics and Astronomy [Southampton], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, 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), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, University of Edinburgh, Jacobs University [Bremen], Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], National Radio Astronomy Observatory (NRAO), Applied Stochastics (IMAPP), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Center for Information Technology CIT, Université de Groningen, Netherlands Foundation for Scientific Research. Joeri van Leeuwen and ThijsCoenen are supported by the Netherlands Research School for Astronomy (GrantNOVA3-NW3-2.3.1), European Project: 224838,EC:FP7:PEOPLE,FP7-PEOPLE-2007-4-3-IRG,PULSARS WITH LOFAR(2008), European Project: 236394,EC:FP7:PEOPLE,FP7-PEOPLE-IEF-2008,PULSAR SURVEY(2010), Hassall, T.E., Stappers, B.W., Hessels, J.W.T., Kramer, M., Alexov, A., Anderson, K., Coenen, T., Karastergiou, A., Keane, E.F., Kondratiev, V.I., Lazaridis, K., Van Leeuwen, J., Noutsos, A., Serylak, M., Sobey, C., Verbiest, J.P.W., Weltevrede, P., Zagkouris, K., Fender, R., Wijers, R.A.M.J., Bähren, L., Bell, M.E., Broderick, J.W., Corbel, S., Daw, E.J., Dhillon, V.S., Eislöffel, J., Falcke, H., Grießmeier, J.-M., Jonker, P., Law, C., Markoff, S., Miller-Jones, J.C.A., Osten, R., Rol, E., Scaife, A.M.M., Scheers, B., Schellart, P., Spreeuw, H., Swinbank, J., Ter Veen, S., Wise, M.W., Wijnands, R., Wucknitz, O., Zarka, P., Asgekar, A., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Boonstra, A.J., Brentjens, M., Brouw, W.N., Brüggen, M., Butcher, H.R., Ciardi, B., Garrett, M.A., Gerbers, M., Gunst, A.W., Van Haarlem, M.P., Heald, G., Hoeft, M., Holties, H., De Jong, A., Koopmans, L.V.E., Kuniyoshi, M., Kuper, G., Loose, G.M., Maat, P., Masters, J., McKean, J.P., Meulman, H., Mevius, M., Munk, H., Noordam, J.E., Orrú, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A., Reich, W., Röttgering, H., Sluman, J., Steinmetz, M., Sterks, C.G.M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Van Weeren, R.J., Wijnholds, S.J., Yatawatta, S., University of Oxford, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen], Harvard University-Smithsonian Institution, Universiteit Leiden, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), High Energy Astrophys. & Astropart. Phys (API, FNWI), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Rhodes University, SKA South Africa, and Ska South Africa

Subjects
010504 meteorology & atmospheric sciences, Astronomy, Magnetosphere, Astrophysics, magnetic fields, 01 natural sciences, law.invention, law, Dispersion (optics), 010303 astronomy & astrophysics, Telescope, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, [PHYS]Physics [physics], Astrophysics::Instrumentation and Methods for Astrophysics, SPECTRAL BEHAVIOR, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Astrophysics - High Energy Astrophysical Phenomena, ARRIVAL-TIME DELAY, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, SUPERDISPERSION DELAY, EMPIRICAL-THEORY, Pulsar, pulsars: general, 0103 physical sciences, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, ISM: general, METIS-287956, Gravitational wave, Astronomy and Astrophysics, telescopes, LOFAR, Astronomy and Astrophysic, EWI-22107, Pulse (physics), PULSES, Interstellar medium, PSR 0809&74, FREQUENCY-DEPENDENCE, Magnetic field, Space and Planetary Science, [SDU]Sciences of the Universe [physics], RADIO-EMISSION, IR-80985, REFRACTION, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], INTERSTELLAR SCATTERING
Abstract

Dispersion in the interstellar medium is a well known phenomenon that follows a simple relationship, which has been used to predict the time delay of dispersed radio pulses since the late 1960s. We performed wide-band simultaneous observations of four pulsars with LOFAR (at 40-190 MHz), the 76-m Lovell Telescope (at 1400 MHz) and the Effelsberg 100-m Telescope (at 8000 MHz) to test the accuracy of the dispersion law over a broad frequency range. In this paper we present the results of these observations which show that the dispersion law is accurate to better than 1 part in 100000 across our observing band. We use this fact to constrain some of the properties of the ISM along the line-of-sight and use the lack of any aberration or retardation effects to determine upper limits on emission heights in the pulsar magnetosphere. We also discuss the effect of pulse profile evolution on our observations, and the implications that it could have for precision pulsar timing projects such as the detection of gravitational waves with pulsar timing arrays., 20 Pages, 14 Figures, Accepted for publication in Astronomy & Astrophysics

Published
2012
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