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Institute
HESS J1943+213
(2018)
Archer, A. ; Benbow, Wystan ; Bird, Ralph ; Brose, Robert ; Buchovecky, M. ; Bugaev, V ; Cui, Wei ; Danie, M. K. ; Falcone, A. ; Feng, Qi ; Finley, John P. ; Flinders, A. ; Fortson, L. ; Furniss, Amy ; Gillanders, Gerard H. ; Huttens, M. ; Hanna, David ; Hervet, O. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Johnson, Caitlin A. ; Kaaret, Philip ; Kar, P. ; Kelley-Hoskins, N. ; Kieda, David ; Krause, Maria ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Lin, T. T. Y. ; McArthur, S. ; Moriarty, P. ; Mukherjee, Reshmi ; Nieto, Daniel ; Ong, R. A. ; Otte, A. N. ; Park, Nahee ; Petrashyk, A. ; Pohl, Martin ; Popkow, Alexis ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynold, P. T. ; Richards, Gregory T. ; Roache, E. ; Rulten, C. ; Sadeh, I ; Sembroski, G. H. ; Shahinyan, Karlen ; Tyler, J. ; Wakely, S. P. ; Weiner, O. M. ; Weinstein, A. ; Wells, R. M. ; Wilcox, P. ; Wilhelm, Alina ; Williams, David A. ; Brisken, W. F. ; Pontrelli, P.
HESS J1943+213 is a very high energy (VHE; > 100 GeV) gamma-ray source in the direction of the Galactic plane. Studies exploring the classification of the source are converging toward its identification as an extreme synchrotron BL Lac object. Here we present 38 hr of VERITAS observations of HESS J1943+213 taken over 2 yr. The source is detected with a significance of similar to 20 standard deviations, showing a remarkably stable flux and spectrum in VHE gamma-rays. Multifrequency Very Long Baseline Array (VLBA) observations of the source confirm the extended, jet-like structure previously found in the 1.6 GHz band with the European VLBI Network and detect this component in the 4.6 and 7.3 GHz bands. The radio spectral indices of the core and the jet and the level of polarization derived from the VLBA observations are in a range typical for blazars. Data from VERITAS, Fermi-LAT, Swift-XRT, the FLWO 48 ' telescope, and archival infrared and hard X-ray observations are used to construct and model the spectral energy distribution (SED) of the source with a synchrotron self-Compton model. The well-measured gamma-ray peak of the SED with VERITAS and Fermi-LAT provides constraining upper limits on the source redshift. Possible contribution of secondary gamma-rays from ultra-high-energy cosmic-ray-initiated electromagnetic cascades to the gamma-ray emission is explored, finding that only a segment of the VHE spectrum can be accommodated with this process. A variability search is performed across X-ray and gamma-ray bands. No statistically significant flux or spectral variability is detected.
Archer, A. ; Benbow, W. ; Bird, R. ; Brose, Robert ; Buchovecky, M. ; Bugaev, V. ; Connolly, M. P. ; Cui, W. ; Daniel, M. K. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Fortson, L. ; Furniss, A. ; Hanna, D. ; Hervet, O. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Hutten, M. ; Johnson, C. A. ; Kaaret, P. ; Kelley-Hoskins, N. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Maier, G. ; McArthur, S. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Park, N. ; Petrashyk, A. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rulten, C. ; Sadeh, I. ; Tyler, J. ; Wakely, S. P. ; Weiner, O. M. ; Wilcox, P. ; Wilhelm, Alina ; Williams, D. A. ; Wissel, S. A. ; Zitzer, B.
We present a new measurement of the energy spectrum of iron nuclei in cosmic rays from 20 TeV to 500 TeV; The measurement makes use of a template-based analysis method, which, for the first time, is applied to the energy reconstruction of iron-induced air showers recorded by the VERITAS array of imaging atmospheric Cherenkov telescopes. The event selection makes use of the direct Cherenkov light which is emitted by charged particles before the first interaction, as well as other parameters related to the shape of the recorded air shower images. The measured spectrum is well described by a power law dF/dE = f(0) center dot (E/E-0)(-gamma) over the full energy range, with gamma = 2.82 +/- 0.30(stat)(-0.27)(+0.24)(syst) and f(0) = (4.82 +/- 0.98(stat)(-2.70)(+2.12)(syst)) x 10(-7) m(-2) s(-1) TeV-1 sr(-1) at E-0 = 50 TeV, with no indication of a cutoff or spectral break. The measured differential flux is compatible with previous results, with improved statistical uncertainty at the highest energies.
Archer, A. ; Benbow, W. ; Bird, R. ; Brose, Robert ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Connolly, M. P. ; Cui, W. ; Daniel, M. K. ; Feng, Q. ; Finley, J. P. ; Fortson, L. ; Furniss, A. ; Gillanders, G. ; Huetten, M. ; Hanna, D. ; Hervet, O. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Lin, T. T. Y. ; Maier, G. ; McArthur, S. ; Moriarty, P. ; Mukherjee, R. ; Ong, R. A. ; Otte, A. N. ; Petrashyk, A. ; Pohl, M. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rulten, C. ; Sadeh, I. ; Santander, M. ; Sembroski, G. H. ; Staszak, D. ; Sushch, I. ; Wakely, S. P. ; Wells, R. M. ; Wilcox, P. ; Wilhelm, Alina ; Williams, D. A. ; Williamson, T. J. ; Zitzer, B.
Cosmic-ray electrons and positrons (CREs) at GeV-TeV energies are a unique probe of our local Galactic neighborhood. CREs lose energy rapidly via synchrotron radiation and inverse-Compton scattering processes while propagating within the Galaxy, and these losses limit their propagation distance. For electrons with TeV energies, the limit is on the order of a kiloparsec. Within that distance, there are only a few known astrophysical objects capable of accelerating electrons to such high energies. It is also possible that the CREs are the products of the annihilation or decay of heavy dark matter (DM) particles. VERITAS, an array of imaging air Cherenkov telescopes in southern Arizona, is primarily utilized for gamma-ray astronomy but also simultaneously collects CREs during all observations. We describe our methods of identifying CREs in VERITAS data and present an energy spectrum, extending from 300 GeV to 5 TeV, obtained from approximately 300 hours of observations. A single power-law fit is ruled out in VERITAS data. We find that the spectrum of CREs is consistent with a broken power law, with a break energy at 710 +/- 40(stat) +/- 140(syst) GeV.
VERITAS and Fermi-LAT Observations of TeV Gamma-Ray Sources Discovered by HAWC in the 2HWC Catalog
(2018)
Abeysekara, A. U. ; Archer, A. ; Benbow, Wystan ; Bird, Ralph ; Brose, Robert ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Chromey, A. J. ; Connolly, M. P. ; Cui, Wei ; Daniel, M. K. ; Falcone, A. ; Feng, Qi ; Finley, John P. ; Fortson, L. ; Furniss, Amy ; Huetten, M. ; Hanna, David ; Hervet, O. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Johnson, Caitlin A. ; Kaaret, Philip ; Kar, P. ; Kertzman, M. ; Kieda, David ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Lin, T. T. Y. ; McArthur, S. ; Moriarty, P. ; Mukherjee, Reshmi ; Ong, R. A. ; Otte, Adam Nepomuk ; Park, Nahee ; Petrashyk, A. ; Pohl, Martin ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, Gregory T. ; Roache, E. ; Rulten, C. ; Sadeh, I. ; Santander, Marcos ; Sembroski, G. H. ; Shahinyan, Karlen ; Sushch, I. ; Tyler, J. ; Wakely, S. P. ; Weinstein, A. ; Wells, R. M. ; Wilcox, P. ; Wilhelm, Alina ; Williams, D. A. ; Williamson, T. J. ; Zitzer, B. ; Abdollahi, S. ; Ajello, Marco ; Baldini, Luca ; Barbiellini, G. ; Bastieri, Denis ; Bellazzini, Ronaldo ; Berenji, B. ; Bissaldi, Elisabetta ; Blandford, R. D. ; Bonino, R. ; Bottacini, E. ; Brandt, Terri J. ; Bruel, P. ; Buehler, R. ; Cameron, R. A. ; Caputo, R. ; Caraveo, P. A. ; Castro, D. ; Cavazzuti, E. ; Charles, Eric ; Chiaro, G. ; Ciprini, S. ; Cohen-Tanugi, Johann ; Costantin, D. ; Cutini, S. ; de Palma, F. ; Di Lalla, N. ; Di Mauro, M. ; Di Venere, L. ; Dominguez, A. ; Favuzzi, C. ; Fegan, S. J. ; Franckowiak, Anna ; Fukazawa, Yasushi ; Funk, Stefan ; Fusco, Piergiorgio ; Gargano, Fabio ; Gasparrini, Dario ; Giglietto, Nicola ; Giordano, F. ; Giroletti, Marcello ; Green, D. ; Grenier, I. A. ; Guillemot, L. ; Guiriec, Sylvain ; Hays, Elizabeth ; Hewitt, John W. ; Horan, D. ; Johannesson, G. ; Kensei, S. ; Kuss, M. ; Larsson, Stefan ; Latronico, L. ; Lemoine-Goumard, Marianne ; Li, J. ; Longo, Francesco ; Loparco, Francesco ; Lovellette, M. N. ; Lubrano, Pasquale ; Magill, Jeffrey D. ; Maldera, Simone ; Mazziotta, Mario Nicola ; McEnery, J. E. ; Michelson, P. F. ; Mitthumsiri, W. ; Mizuno, Tsunefumi ; Monzani, Maria Elena ; Morselli, Aldo ; Moskalenko, Igor V. ; Negro, M. ; Nuss, E. ; Ojha, R. ; Omodei, Nicola ; Orienti, M. ; Orlando, E. ; Palatiello, M. ; Paliya, Vaidehi S. ; Paneque, D. ; Perkins, Jeremy S. ; Persic, M. ; Pesce-Rollins, Melissa ; Petrosian, Vahe' ; Piron, F. ; Porter, Troy A. ; Principe, G. ; Raino, S. ; Rando, Riccardo ; Rani, B. ; Razzano, Massimilano ; Razzaque, Soebur ; Reimer, A. ; Reimer, Olaf ; Reposeur, T. ; Sgro, C. ; Siskind, E. J. ; Spandre, Gloria ; Spinelli, P. ; Suson, D. J. ; Tajima, Hiroyasu ; Thayer, J. B. ; Thompson, David J. ; Torres, Diego F. ; Tosti, Gino ; Troja, Eleonora ; Valverde, J. ; Vianello, Giacomo ; Vogel, M. ; Wood, K. ; Yassine, M. ; Alfaro, R. ; Alvarez, C. ; Alvarez, J. D. ; Arceo, R. ; Arteaga-Velazquez, J. C. ; Rojas, D. Avila ; Ayala Solares, H. A. ; Becerril, A. ; Belmont-Moreno, E. ; BenZvi, S. Y. ; Bernal, A. ; Braun, J. ; Brisbois, C. ; Caballero-Mora, K. S. ; Capistran, T. ; Carraminana, A. ; Casanova, Sabrina ; Castillo, M. ; Cotti, U. ; Cotzomi, J. ; Coutino de Leon, S. ; De Leon, C. ; De la Fuente, E. ; Dichiara, S. ; Dingus, B. L. ; DuVernois, M. A. ; Diaz-Velez, J. C. ; Engel, K. ; Enriquez-Rivera, O. ; Fiorino, D. W. ; Fleischhack, H. ; Fraija, N. ; Garcia-Gonzalez, J. A. ; Garfias, F. ; Gonzalez Munoz, A. ; Gonzalez, M. M. ; Goodman, J. A. ; Hampel-Arias, Z. ; Harding, J. P. ; Hernandez, S. ; Hernandez-Almada, A. ; Hona, B. ; Hueyotl-Zahuantitla, F. ; Hui, C. M. ; Huntemeyer, P. ; Iriarte, A. ; Jardin-Blicq, A. ; Joshi, V. ; Kaufmann, S. ; Lara, A. ; Lauer, R. J. ; Lee, W. H. ; Lennarz, D. ; Leon Vargas, H. ; Linnemann, J. T. ; Longinotti, A. L. ; Luis-Raya, G. ; Luna-Garcia, R. ; Lopez-Coto, R. ; Malone, K. ; Marinelli, S. S. ; Martinez, O. ; Martinez-Castellanos, I. ; Martinez-Castro, J. ; Martinez-Huerta, H. ; Matthews, J. A. ; Miranda-Romagnoli, P. ; Moreno, E. ; Mostafa, M. ; Nayerhoda, A. ; Nellen, L. ; Newbold, M. ; Nisa, M. U. ; Noriega-Papaqui, R. ; Pelayo, R. ; Pretz, J. ; Perez-Perez, E. G. ; Ren, Z. ; Rho, C. D. ; Riviere, C. ; Rosa-Gonzalez, D. ; Rosenberg, M. ; Ruiz-Velasco, E. ; Salazar, H. ; Greus, F. Salesa ; Sandoval, A. ; Schneider, M. ; Arroyo, M. Seglar ; Sinnis, G. ; Smith, A. J. ; Springer, R. W. ; Surajbali, P. ; Taboada, Ignacio ; Tibolla, O. ; Tollefson, K. ; Torres, I. ; Ukwatta, Tilan N. ; Villasenor, L. ; Weisgarber, T. ; Westerhoff, Stefan ; Wisher, I. G. ; Wood, J. ; Yapici, Tolga ; Yodh, G. ; Zepeda, A. ; Zhou, H.
The High Altitude Water Cherenkov (HAWC) collaboration recently published their 2HWC catalog, listing 39 very high energy (VHE; >100 GeV) gamma-ray sources based on 507 days of observation. Among these, 19 sources are not associated with previously known teraelectronvolt (TeV) gamma-ray sources. We have studied 14 of these sources without known counterparts with VERITAS and Fermi-LAT. VERITAS detected weak gamma-ray emission in the 1 TeV-30 TeV band in the region of DA 495, a pulsar wind nebula coinciding with 2HWC J1953+294, confirming the discovery of the source by HAWC. We did not find any counterpart for the selected 14 new HAWC sources from our analysis of Fermi-LAT data for energies higher than 10 GeV. During the search, we detected gigaelectronvolt (GeV) gamma-ray emission coincident with a known TeV pulsar wind nebula, SNR G54.1+0.3 (VER J1930+188), and a 2HWC source, 2HWC J1930+188. The fluxes for isolated, steady sources in the 2HWC catalog are generally in good agreement with those measured by imaging atmospheric Cherenkov telescopes. However, the VERITAS fluxes for SNR G54.1+0.3, DA 495, and TeV J2032+4130 are lower than those measured by HAWC, and several new HAWC sources are not detected by VERITAS. This is likely due to a change in spectral shape, source extension, or the influence of diffuse emission in the source region.
Abeysekara, A. U. ; Benbow, Wystan ; Bird, Ralph ; Brill, A. ; Brose, Robert ; Buckley, J. H. ; Chromey, A. J. ; Daniel, M. K. ; Falcone, A. ; Finley, J. P. ; Fortson, L. ; Furniss, Amy ; Gent, A. ; Gillanders, Gerald H. ; Hanna, David ; Hassan, T. ; Hervet, O. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Kaaret, Philip ; Kar, P. ; Kertzman, M. ; Kieda, David ; Krause, Maria ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Lin, T. T. Y. ; Maier, Gernot ; Moriarty, P. ; Mukherjee, Reshmi ; Ong, R. A. ; Otte, Adam Nepomuk ; Park, Nahee ; Petrashyk, A. ; Pohl, Martin ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Richards, Gregory T. ; Roache, E. ; Sadeh, I. ; Santander, Marcos ; Schlenstedt, S. ; Sembroski, G. H. ; Sushch, Iurii ; Tyler, J. ; Vassiliev, V. V. ; Wakely, S. P. ; Weinstein, A. ; Wells, R. M. ; Wilcox, P. ; Wilhelm, Alina ; Williams, David A. ; Williamson, T. J. ; Zitzer, B. ; Acciari, V. A. ; Ansoldi, S. ; Antonelli, L. A. ; Engels, A. Arbet ; Baack, D. ; Babic, A. ; Banerjee, B. ; de Almeida, U. Barres ; Barrio, J. A. ; Becerra Gonzalez, Josefa ; Bednarek, Wlodek ; Bernardini, Elisa ; Berti, A. ; Besenrieder, J. ; Bhattacharyya, W. ; Bigongiari, C. ; Biland, A. ; Blanch, O. ; Bonnoli, G. ; Busetto, G. ; Carosi, R. ; Ceribella, G. ; Cikota, S. ; Colak, S. M. ; Colin, P. ; Colombo, E. ; Contreras, J. L. ; Cortina, J. ; Covino, S. ; Da Vela, P. ; Dazzi, F. ; De Angelis, A. ; De Lotto, B. ; Delfino, M. ; Delgado, J. ; Di Pierro, F. ; Do Souto Espinera, E. ; Dominguez, A. ; Prester, D. Dominis ; Dorner, D. ; Doro, M. ; Einecke, S. ; Elsaesser, D. ; Ramazani, V. Fallah ; Fattorini, A. ; Fernandez-Barral, A. ; Ferrara, G. ; Fidalgo, D. ; Foffano, L. ; Fonseca, M. V. ; Font, L. ; Fruck, C. ; Galindo, D. ; Gallozzi, S. ; Lopez, R. J. Garcia ; Garczarczyk, M. ; Gasparyan, S. ; Gaug, Markus ; Giammaria, P. ; Godinovic, N. ; Guberman, D. ; Hadasch, D. ; Hahn, A. ; Herrera, J. ; Hoang, J. ; Hrupec, D. ; Inoue, S. ; Ishio, K. ; Iwamura, Y. ; Kubo, H. ; Kushida, J. ; Kuvezdic, D. ; Lamastra, A. ; Lelas, D. ; Leone, Francesco ; Lindfors, E. ; Lombardi, S. ; Longo, Francesco ; Lopez, M. ; Lopez-Oramas, A. ; Machado de Oliveira Fraga, B. ; Maggio, C. ; Majumdar, P. ; Makariev, M. ; Mallamaci, M. ; Maneva, G. ; Manganaro, M. ; Mannheim, K. ; Maraschi, L. ; Mariotti, M. ; Martinez, M. ; Masuda, S. ; Mazin, D. ; Minev, M. ; Miranda, J. M. ; Mirzoyan, R. ; Molina, E. ; Moralejo, A. ; Moreno, V. ; Moretti, E. ; Munar-Adrover, Pere ; Neustroev, V. ; Niedzwiecki, Andrzej ; Rosillo, Mireia Nievas ; Nigro, C. ; Nilsson, Kari ; Ninci, D. ; Nishijima, K. ; Noda, K. ; Nogues, L. ; Noethe, M. ; Paiano, Simona ; Palacio, J. ; Paneque, D. ; Paoletti, R. ; Paredes, J. M. ; Pedaletti, G. ; Penil, P. ; Peresano, M. ; Persic, M. ; Moroni, P. G. Prada ; Prandini, E. ; Puljak, I. ; Garcia, J. R. ; Rhode, W. ; Ribo, Marc ; Rico, J. ; Righi, C. ; Rugliancich, A. ; Saha, Lab ; Sahakyan, Narek ; Saito, T. ; Satalecka, K. ; Schweizer, T. ; Sitarek, J. ; Snidaric, I. ; Sobczynska, D. ; Somero, A. ; Stamerra, A. ; Strzys, M. ; Suric, T. ; Tavecchio, Fabrizio ; Temnikov, P. ; Terzic, T. ; Teshima, M. ; Torres-Alba, N. ; Tsujimoto, S. ; van Scherpenberg, J. ; Vanzo, G. ; Vazquez Acosta, M. ; Vovk, I. ; Will, M. ; Zaric, D.
We report on observations of the pulsar/Be star binary system PSR J2032+4127/MT91 213 in the energy range between 100 GeV and 20 TeV with the Very Energetic Radiation Imaging Telescope Array and Major Atmospheric Gamma Imaging Cherenkov telescope arrays. The binary orbit has a period of approximately 50 years, with the most recent periastron occurring on 2017 November 13. Our observations span from 18 months prior to periastron to one month after. A new point-like gamma-ray source is detected, coincident with the location of PSR J2032+4127/MT91 213. The gamma-ray light curve and spectrum are well characterized over the periastron passage. The flux is variable over at least an order of magnitude, peaking at periastron, thus providing a firm association of the TeV source with the pulsar/Be star system. Observations prior to periastron show a cutoff in the spectrum at an energy around 0.5 TeV. This result adds a new member to the small population of known TeV binaries, and it identifies only the second source of this class in which the nature and properties of the compact object are firmly established. We compare the gamma-ray results with the light curve measured with the X-ray Telescope on board the Neil Gehrels Swift Observatory and with the predictions of recent theoretical models of the system. We conclude that significant revision of the models is required to explain the details of the emission that we have observed, and we discuss the relationship between the binary system and the overlapping steady extended source, TeV J2032+4130.
Benbow, W. ; Bird, R. ; Brill, A. ; Brose, Robert ; Chromey, A. J. ; Daniel, M. K. ; Feng, Q. ; Finley, J. P. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Giuri, C. ; Gueta, O. ; Hanna, D. ; Halpern, J. P. ; Hassan, Tarek ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Joyce, Amy M. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Lang, M. J. ; Lin, T. T. Y. ; Maier, Gernot ; Matthews, N. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Nievas-Rosillos, M. ; Ong, R. A. ; Park, N. ; Petrashyk, A. ; Pohl, Martin ; Pueschel, Elisa ; Quinn, John ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rulten, C. ; Sadeh, Iftach ; Santander, M. ; Sembroski, G. H. ; Shahinyan, K. ; Sushch, Iurii ; Wakely, S. P. ; Wells, R. M. ; Wilcox, P. ; Wilhelm, Alina ; Williams, David A. ; Williamson, T. J.
The angular size of a star is a critical factor in determining its basic properties1. Direct measurement of stellar angular diameters is difficult: at interstellar distances stars are generally too small to resolve by any individual imaging telescope. This fundamental limitation can be overcome by studying the diffraction pattern in the shadow cast when an asteroid occults a star2, but only when the photometric uncertainty is smaller than the noise added by atmospheric scintillation3. Atmospheric Cherenkov telescopes used for particle astrophysics observations have not generally been exploited for optical astronomy due to the modest optical quality of the mirror surface. However, their large mirror area makes them well suited for such high-time-resolution precision photometry measurements4. Here we report two occultations of stars observed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS)5 Cherenkov telescopes with millisecond sampling, from which we are able to provide a direct measurement of the occulted stars’ angular diameter at the ≤0.1 mas scale. This is a resolution never achieved before with optical measurements and represents an order of magnitude improvement over the equivalent lunar occultation method6. We compare the resulting stellar radius with empirically derived estimates from temperature and brightness measurements, confirming the latter can be biased for stars with ambiguous stellar classifications.
Allen, C. ; Archambault, S. ; Archer, A. ; Benbow, W. ; Bird, R. ; Bourbeau, E. ; Brose, Robert ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Cardenzana, J. V. ; Cerruti, M. ; Chen, Xuhui ; Christiansen, J. L. ; Connolly, M. P. ; Cui, W. ; Daniel, M. K. ; Eisch, J. D. ; Falcone, Abe ; Feng, Q. ; Fernandez-Alonso, M. ; Finley, J. P. ; Fleischhack, H. ; Flinders, A. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Huetten, M. ; Hakansson, N. ; Hanna, D. ; Hervet, O. ; Holder, J. ; Hughes, G. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Maier, G. ; McArthur, S. ; McCann, A. ; Meagher, K. ; Moriarty, P. ; Mukherjee, R. ; Nguyen, T. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Park, N. ; Petrashyk, A. ; Pichel, A. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rovero, A. C. ; Rulten, C. ; Sadeh, I. ; Santander, Marcos ; Sembroski, G. H. ; Shahinyan, K. ; Telezhinsky, Igor O. ; Tucci, J. V. ; Tyler, J. ; Wakely, S. P. ; Weinstein, A. ; Wilhelm, Alina ; Williams, D. A.
We present very-high-energy gamma-ray observations of the BL Lac object 1ES 2344+514 taken by the Very Energetic Radiation Imaging Telescope Array System between 2007 and 2015. 1ES 2344+514 is detected with a statistical significance above the background of 20.8 sigma in 47.2 h (livetime) of observations, making this the most comprehensive very-high-energy study of 1ES 2344+514 to date. Using these observations, the temporal properties of 1ES 2344+514 are studied on short and long times-scales. We fit a constant-flux model to nightly and seasonally binned light curves and apply a fractional variability test to determine the stability of the source on different time-scales. We reject the constant-flux model for the 2007-2008 and 2014-2015 nightly binned light curves and for the long-term seasonally binned light curve at the > 3 sigma level. The spectra of the time-averaged emission before and after correction for attenuation by the extragalactic background light are obtained. The observed time-averaged spectrum above 200 GeV is satisfactorily fitted (x(2)/NDF = 7.89/6) by a power-law function with an index Gamma = 2.46 +/- 0.06(stat) +/- 0.20(sys) and extends to at least 8 TeV. The extragalactic-backgroundlight-deabsorbed spectrum is adequately fit (x(2)/NDF = 6.73/6) by a power-law function with an index Gamma = 2.15 +/- 0.06(stat) +/- 0.20(sys) while an F-test indicates that the power law with an exponential cut-off function provides a marginally better fit (x(2)/NDF = 2.56/5) at the 2.1 sigma level. The source location is found to be consistent with the published radio location and its spatial extent is consistent with a point source.
Discovery of Very-high-energy Emission from RGB J2243+203 and Derivation of Its Redshift Upper Limit
(2017)
Abeysekara, A. U. ; Archambault, S. ; Archer, A. ; Benbow, W. ; Bird, R. ; Brose, Robert ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Cerruti, M. ; Connolly, M. P. ; Cui, W. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Huetten, M. ; Hanna, D. ; Hervet, O. ; Holder, J. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Maier, G. ; McArthur, S. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Park, N. ; Petrashyk, A. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rulten, C. ; Sadeh, I. ; Santander, M. ; Sembroski, G. H. ; Shahinyan, K. ; Staszak, D. ; Telezhinsky, Igor O. ; Tyler, J. ; Vassiliev, V. V. ; Wakely, S. P. ; Weiner, O. M. ; Weinstein, A. ; Wilcox, P. ; Wilhelm, Alina ; Williams, D. A. ; Zitzer, B.
Very-high-energy (VHE; > 100 GeV) gamma-ray emission from the blazar RGB J2243+203 was discovered with the VERITAS Cherenkov telescope array, during the period between 2014 December 21 and 24. The VERITAS energy spectrum from this source can be fitted by a power law with a photon index of 4.6 +/- 0.5, and a flux normalization at 0.15 TeV of (6.3 +/- 1.1) x 10(-10) cm(-2) s(-1) TeV-1. The integrated Fermi-LAT flux from 1 to 100 GeV during the VERITAS detection is (4.1 +/- 0.8) x 10(-8) cm(-2) s(-1), which is an order of magnitude larger than the four-year-averaged flux in the same energy range reported in the 3FGL catalog, (4.0 +/- 0.1 x 10(-9) cm(-2) s(-1)). The detection with VERITAS triggered observations in the X-ray band with the Swift-XRT. However, due to scheduling constraints Swift-XRT observations were performed 67 hr after the VERITAS detection, rather than simultaneously with the VERITAS observations. The observed X-ray energy spectrum between 2 and 10 keV can be fitted with a power law with a spectral index of 2.7 +/- 0.2, and the integrated photon flux in the same energy band is (3.6 +/- 0.6) x 10(-13) cm(-2) s(-1). EBL-model-dependent upper limits of the blazar redshift have been derived. Depending on the EBL model used, the upper limit varies in the range from z < 0.9 to z < 1.1.
Archambault, S. ; Archer, A. ; Aune, T. ; Barnacka, Anna ; Benbow, W. ; Bird, R. ; Buchovecky, M. ; Buckley, J. H. ; Bugaev, V. ; Byrum, K. ; Cardenzana, J. V. ; Cerruti, M. ; Chen, Xuhui ; Ciupik, L. ; Collins-Hughes, E. ; Connolly, M. P. ; Cui, W. ; Dickinson, H. J. ; Dumm, J. ; Eisch, J. D. ; Falcone, A. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Flinders, A. ; Fortin, P. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Gyuk, G. ; Huetten, M. ; Hakansson, Nils ; Hanna, D. ; Holder, J. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Maier, G. ; McArthur, S. ; McCann, A. ; Meagher, K. ; Millis, J. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Pandel, D. ; Park, N. ; Pelassa, V. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Rousselle, J. ; Rulten, C. ; Santander, M. ; Sembroski, G. H. ; Shahinyan, K. ; Smith, A. W. ; Staszak, D. ; Telezhinsky, Igor O. ; Tucci, J. V. ; Tyler, J. ; Vincent, S. ; Wakely, S. P. ; Weiner, O. M. ; Weinstein, A. ; Wilhelm, Alina ; Williams, D. A. ; Zitzer, B.
The TeV binary system LS I +61 degrees 303 is known for its regular, non-thermal emission pattern that traces the orbital period of the compact object in its 26.5 day orbit around its B0 Ve star companion. The system typically presents elevated TeV emission around apastron passage with flux levels between 5% and 15% of the steady flux from the Crab Nebula (> 300 GeV). In this article, VERITAS observations of LS I + 61 degrees. 303 taken in late 2014 are presented, during which bright TeV flares around apastron at flux levels peaking above 30% of the Crab Nebula flux were detected. This is the brightest such activity from this source ever seen in the TeV regime. The strong outbursts have rise and fall times of less than a day. The short timescale of the flares, in conjunction with the observation of 10 TeV photons from LS I + 61 degrees 303 during the flares, provides constraints on the properties of the accelerator in the source.
Abeysekara, A. U. ; Archambault, S. ; Archer, A. ; Benbow, W. ; Bird, R. ; Buchovecky, M. ; Buckley, J. H. ; Byrum, K. ; Cardenzana, J. V. ; Cerruti, M. ; Chen, Xuhui ; Christiansen, J. L. ; Ciupik, L. ; Cui, W. ; Dickinson, H. J. ; Eisch, J. D. ; Errando, M. ; Falcone, A. ; Fegan, D. J. ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Fortin, P. ; Fortson, L. ; Furniss, A. ; Gillanders, G. H. ; Griffin, S. ; Grube, J. ; Gyuk, G. ; Huetten, M. ; Hakansson, Nils ; Hanna, D. ; Holder, J. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kar, P. ; Kelley-Hoskins, N. ; Kertzman, M. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Kumar, S. ; Lang, M. J. ; Lin, T. T. Y. ; Maier, G. ; McArthur, S. ; McCann, A. ; Meagher, K. ; Moriarty, P. ; Mukherjee, R. ; Nieto, D. ; Ong, R. A. ; Otte, A. N. ; Park, N. ; Perkins, J. S. ; Petrashyk, A. ; Pohl, Martin ; Popkow, A. ; Pueschel, Elisa ; Quinn, J. ; Ragan, K. ; Ratliff, G. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Santander, M. ; Sembroski, G. H. ; Shahinyan, K. ; Staszak, D. ; Telezhinsky, Igor O. ; Tucci, J. V. ; Tyler, J. ; Vincent, S. ; Wakely, S. P. ; Weiner, O. M. ; Weinstein, A. ; Williams, D. A. ; Zitzer, B.
The F-type star KIC. 8462852 has recently been identified as an exceptional target for search for extraterrestrial intelligence (SETI) observations. We describe an analysis methodology for optical SETI, which we have used to analyze nine hours of serendipitous archival observations of KIC. 8462852 made with the VERITAS gamma-ray observatory between 2009 and 2015. No evidence of pulsed optical beacons, above a pulse intensity at the Earth of approximately 1 photon m(-2), is found. We also discuss the potential use of imaging atmospheric Cherenkov telescope arrays in searching for extremely short duration optical transients in general.