Author: "Zitzer, B" - Searchworks@Jio Institute Digital Library Search Results

Your search keyword '"Zitzer, B"' showing total 555 results

Start Over Author "Zitzer, B"

555 results on '"Zitzer, B"'

1. Evidence for proton acceleration up to TeV energies based on VERITAS and Fermi-LAT observations of the Cas A SNR

Author: Abeysekara, A. U., Archer, A., Benbow, W., Bird, R., Brose, R., Buchovecky, M., Buckley, J. H., Chromey, A. J., Cui, W., Daniel, M. K., Das, S., Dwarkadas, V. V., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Maier, G., Moriarty, P., Mukherjee, R., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Park, N., Petrashyk, A., Pfrang, K., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Sushch, I., Weinstein, A., Wilcox, P., Wilhelm, A., Williams, D. A., Williamson, T. J, Zitzer, B., and Ghiotto, A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present a study of $\gamma$-ray emission from the core-collapse supernova remnant Cas~A in the energy range from 0.1GeV to 10TeV. We used 65 hours of VERITAS data to cover 200 GeV - 10 TeV, and 10.8 years of \textit{Fermi}-LAT data to cover 0.1-500 GeV. The spectral analysis of \textit{Fermi}-LAT data shows a significant spectral curvature around $1.3 \pm 0.4_{stat}$ GeV that is consistent with the expected spectrum from pion decay. Above this energy, the joint spectrum from \textit{Fermi}-LAT and VERITAS deviates significantly from a simple power-law, and is best described by a power-law with spectral index of $2.17\pm 0.02_{stat}$ with a cut-off energy of $2.3 \pm 0.5_{stat}$ TeV. These results, along with radio, X-ray and $\gamma$-ray data, are interpreted in the context of leptonic and hadronic models. Assuming a one-zone model, we exclude a purely leptonic scenario and conclude that proton acceleration up to at least 6 TeV is required to explain the observed $\gamma$-ray spectrum. From modeling of the entire multi-wavelength spectrum, a minimum magnetic field inside the remnant of $B_{\mathrm{min}}\approx150\,\mathrm{\mu G}$ is deduced., Comment: 33 pages, 9 Figures, 6 Tables
Published: 2020
Full Text: View/download PDF

2. The Great Markarian 421 Flare of February 2010: Multiwavelength variability and correlation studies

Author: Abeysekara, A. U., Benbow, W., Bird, R., Brill, A., Brose, R., Buchovecky, M., Buckley, J. H., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Dumm, J., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Galante, N., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hassan, T., 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., Moriarty, P., Mukherjee, R., Nelson, T., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pichel, A., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Stevenson, B., Sushch, I., Tyler, J., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Zitzer, B., Acciari, V. A., Ansoldi, S., Antonelli, L. A., Engels, A. Arbet, Baack, D., Babić, A., Banerjee, B., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Bellizzi, L., Bernardini, E., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Busetto, G., Carosi, R., Ceribella, G., Chai, Y., Cikota, S., Colak, S. M., Colin, U., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Di Pierro, F., Espiñera, E. Do Souto, Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Elsaesser, D., Ramazani, V. Fallah, Fattorini, A., Fernández-Barral, A., Ferrara, G., Fidalgo, D., Foffano, L., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., Gallozzi, S., López, R. J. García, Garczarczyk, M., Gasparyan, S., Gaug, M., Godinović, N., Green, D., Guberman, D., Hadasch, D., Hahn, A., Herrera, J., Hoang, J., Hrupec, D., Inoue, S., Ishio, K., Iwamura, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., López, M., López-Coto, R., López-Oramas, A., Fraga, B. Machado de Oliveira, Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Masuda, S., Mazin, D., Miceli, D., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Munar-Adrover, P., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogués, L., Nöthe, M., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Peñil, P., Peresano, M., Persic, M., Moroni, P. G. Prada, Prandini, E., Puljak, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Satalecka, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Somero, A., Stamerra, A., Strom, D., Strzys, M., Sun, S., Surić, T., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Torres-Albà, N., Tsujimoto, S., van Scherpenberg, J., Vanzo, G., Acosta, M. Vazquez, Vovk, I., Will, M., Zarić, D., Aller, H. D., Aller, M. F., Carini, M. T., Horan, D., Jordan, B., Jorstad, Svetlana G., Kurtanidze, O. M., Kurtanidze, S. O., Lähteenmäki, A., Larionov, V. M., Larionova, E. G., Madejski, G., Marscher, Alan P., Max-Moerbeck, W., Moody, J. Ward, Morozova, D. A., Nikolashvili, M. G., Raiteri, C. M., Readhead, A. C. S., Richards, J. L., Sadun, Alberto C., Sakamoto, T., Sigua, L. A., Smith, P. S., Talvikki, H., Tammi, J., Tornikoski, M., Troitsky, I. S., and Villata, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during the month of February, 2010 when an extraordinary flare reaching a level of $\sim$27~Crab Units above 1~TeV was measured in very-high-energy (VHE) $\gamma$-rays with the VERITAS observatory. This is the highest flux state for Mrk 421 ever observed in VHE $\gamma$-rays. Data are analyzed from a coordinated campaign across multiple instruments including VHE $\gamma$-ray (VERITAS, MAGIC), high-energy (HE) $\gamma$-ray (Fermi-LAT), X-ray (Swift}, RXTE, MAXI), optical (including the GASP-WEBT collaboration and polarization data) and radio (Mets\"ahovi, OVRO, UMRAO). Light curves are produced spanning multiple days before and after the peak of the VHE flare, including over several flare `decline' epochs. The main flare statistics allow 2-minute time bins to be constructed in both the VHE and optical bands enabling a cross-correlation analysis that shows evidence for an optical lag of $\sim$25-55 minutes, the first time-lagged correlation between these bands reported on such short timescales. Limits on the Doppler factor ($\delta \gtrsim 33$) and the size of the emission region ($ \delta^{-1}R_B \lesssim 3.8\times 10^{13}\,\,\mbox{cm}$) are obtained from the fast variability observed by VERITAS during the main flare. Analysis of 10-minute-binned VHE and X-ray data over the decline epochs shows an extraordinary range of behavior in the flux-flux relationship: from linear to quadratic to lack of correlation to anti-correlation. Taken together, these detailed observations of an unprecedented flare seen in Mrk 421 are difficult to explain by the classic single-zone synchrotron self-Compton model., Comment: 41 pages including 3 appendices, 13 figures; version accepted to Astrophysical Journal
Published: 2020
Full Text: View/download PDF

3. Measurement of the extragalactic background light spectral energy distribution with VERITAS

Author: VERITAS collaboration, Abeysekara, A. U., Archer, A., Benbow, W., Bird, R., Brill, A., Brose, R., Buchovecky, M., Christiansen, J. L., Cui, W., Daniel, M. K., Falcone, A., Feng, Q., Fernandez-Alonso, M., Finley, J. P., Fortson, L., Furniss, A., Gent, A., Giuri, C., Gueta, O., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Maier, G., Moriarty, P., Mukherjee, R., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Ragan, K., Reynolds, P. T., Ribeiro, D., Richards, G. T., Roache, E., Rovero, A. C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Sushch, I., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Williamson, T. J, and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The extragalactic background light (EBL), a diffuse photon field in the optical and infrared range, is a record of radiative processes over the Universe's history. Spectral measurements of blazars at very high energies ($>$100 GeV) enable the reconstruction of the spectral energy distribution (SED) of the EBL, as the blazar spectra are modified by redshift- and energy-dependent interactions of the gamma-ray photons with the EBL. The spectra of 14 VERITAS-detected blazars are included in a new measurement of the EBL SED that is independent of EBL SED models. The resulting SED covers an EBL wavelength range of 0.56--56 $\mu$m, and is in good agreement with lower limits obtained by assuming that the EBL is entirely due to radiation from cataloged galaxies., Comment: Accepted for publication in The Astrophysical Journal
Published: 2019
Full Text: View/download PDF

4. Long-term gamma-ray observations of the binary HESS J0632+057 with H.E.S.S., MAGIC and VERITAS

Author: Maier, G., Blanch, O., Hadasch, D., López-Oramas, A., Komin, N., Lundy, M., Malyshev, D., Moepi, J., Ohm, S., Pühlhofer, G., Prado, R., Schlenstedt, S., Torres, D. F., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The gamma-ray binary HESS J0632+057 has been observed at very-high energies (E $>$ 100 GeV) for more than ten years by the major systems of imaging atmospheric Cherenkov telescopes. We present a summary of results obtained with the H.E.S.S., MAGIC, and VERITAS experiments based on roughly 440 h of observations in total. This includes a discussion of an unusually bright TeV outburst of HESS J0632+057 in January 2018. The updated gamma-ray light curve now covers all phases of the orbital period with significant detections in almost all orbital phases. Results are discussed in context with simultaneous observations with the X-ray Telescope onboard the Neil Gehrels Swift Observatory., Comment: Proceedings of the 36th International Cosmic Ray Conference (ICRC2019) Madison, WI July 24-Aug 1, 2019
Published: 2019

5. A Search for Pulsed Very High-Energy Gamma Rays from Thirteen Young Pulsars in Archival VERITAS Data

Author: Archer, A., Benbow, W., Bird, R., Brose, R., Buchovecky, M., Buckley, J. H., Chromey, A. J., Cui, W., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gent, A., Gueta, O., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krennrich, F., Kumar, S., Lang, M. J., Lin, T. T. Y., McCann, A., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Otte, A. N., Pandel, D., Park, N., Petrashyk, A., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Richards, G. T., Roache, E., Sadeh, I., Santander, M., Scott, S. S., Sembroski, G. H., Shahinyan, K., Sushch, I., Tyler, J., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Williamson, T. J, and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We conduct a search for periodic emission in the very high-energy gamma-ray band (VHE; E > 100 GeV) from a total of 13 pulsars in an archival VERITAS data set with a total exposure of over 450 hours. The set of pulsars includes many of the brightest young gamma-ray pulsars visible in the Northern Hemisphere. The data analysis resulted in non-detections of pulsed VHE gamma rays from each pulsar. Upper limits on a potential VHE gamma-ray flux are derived at the 95% confidence level above three energy thresholds using two methods. These are the first such searches for pulsed VHE emission from each of the pulsars, and the obtained limits constrain a possible flux component manifesting at VHEs as is seen for the Crab pulsar., Comment: 32 pages, 20 figures, accepted for publication in ApJ
Published: 2019
Full Text: View/download PDF

6. Periastron Observations of TeV Gamma-Ray Emission from a Binary System with a 50-year Period

Author: The VERITAS Collaboration, Abeysekara, A. U., Benbow, W., Bird, R., Brill, A., Brose, R., Buckley, J. H., Chromey, A. J., Daniel, M. K., Falcone, A., Finley, J. P., Fortson, L., Furniss, A., Gent, A., Gillanders, G. H., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Kaaret, P., Kar, P., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Lin, T. T. Y., Maier, G., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Richards, G. T., Roache, E., Sadeh, I., Santander, M., Schlenstedt, S., Sembroski, G. H., Sushch, I., Tyler, J., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Williamson, T. J, Zitzer, B., Collaboration, MAGIC, Acciari, V. A., Ansoldi, S., Antonelli, L. A., Engels, A. Arbet, Baack, D., Babić, A., Banerjee, B., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Bernardini, E., 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., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Di Pierro, F., Espiñera, E. Do Souto, Domínguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Elsaesser, D., Ramazani, V. Fallah, Fattorini, A., Fernández-Barral, A., Ferrara, G., Fidalgo, D., Foffano, L., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., Gallozzi, S., López, R. J. García, Garczarczyk, M., Gasparyan, S., Gaug, M., Giammaria, P., Godinović, N., Guberman, D., Hadasch, D., Hahn, A., Herrera, J., Hoang, J., Hrupec, D., Inoue, S., Ishio, K., Iwamura, Y., Kubo, H., Kushida, J., Kuveždić, D., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Lombardi, S., Longo, F., López, M., López-Oramas, A., Fraga, B. Machado de Oliveira, Maggio, C., Majumdar, P., Makariev, M., Mallamaci, M., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Masuda, S., Mazin, D., Minev, M., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Moreno, V., Moretti, E., Munar-Adrover, P., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogués, L., Nöthe, M., Paiano, S., Palacio, J., Paneque, D., Paoletti, R., Paredes, J. M., Pedaletti, G., Peñil, P., Peresano, M., Persic, M., Moroni, P. G. Prada, Prandini, E., Puljak, I., Garcia, J. R., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Satalecka, K., Schweizer, T., Sitarek, J., Šnidarić, I., Sobczynska, D., Somero, A., Stamerra, A., Strzys, M., Surić, T., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Torres-Albà, N., Tsujimoto, S., van Scherpenberg, J., Vanzo, G., Acosta, M. Vazquez, Vovk, I., Will, M., and Zarić, D.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: 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 VERITAS and MAGIC imaging atmospheric 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 (XRT) on board the Neil Gehrels \textit{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 we have observed, and we discuss the relationship between the binary system and the overlapping steady extended source, TeV J2032+4130., Comment: 12 pages, 3 figures, 1 table. Accepted for publication in ApJL
Published: 2018
Full Text: View/download PDF

7. VERITAS and Fermi-LAT observations of new HAWC sources

Author: VERITAS Collaboration, Abeysekara, A. U., Archer, A., Benbow, W., Bird, R., Brose, R., Buchovecky, M., Buckley, J. H., Bugaev, V., Chromey, A. J., Connolly, M. P., Cui, W., Daniel, M. K., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Hutten, M., Hanna, D., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Lin, T. T. Y., McArthur, S., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Sushch, I., Tyler, J., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Williamson, T. J., Zitzer, B., Collaboration, Fermi-LAT, Abdollahi, S., Ajello, M., Baldini, L., Barbiellini, G., Bastieri, D., Bellazzini, R., Berenji, B., Bissaldi, E., Blandford, R. D., Bonino, R., Bottacini, E., Brandt, T. J., Bruel, P., Buehler, R., Cameron, R. A., Caputo, R., Caraveo, P. A., Castro, D., Cavazzuti, E., Charles, E., Chiaro, G., Ciprini, S., Cohen-Tanugi, J., Costantin, D., Cutini, S., D'Ammando, F., de Palma, F., Di Lalla, N., Di Mauro, M., Di Venere, L., Dominguez, A., Favuzzi, C., Fegan, S. J., Franckowiak, A., Fukazawa, Y., Funk, S., Fusco, P., Gargano, F., Gasparrini, D., Giglietto, N., Giordano, F., Giroletti, M., Green, D., Grenier, I. A., Guillemot, L., Guiriec, S., Hays, E., Hewitt, J. W., Horan, D., Johannesson, G., Kensei, S., Kuss, M., Larsson, S., Latronico, L., Lemoine-Goumard, M., Li, J., Longo, F., Loparco, F., Lovellette, M. N., Lubrano, P., Magill, J. D., Maldera, S., Mazziotta, M. N., McEnery, J. E., Michelson, P. F., Mitthumsiri, W., Mizuno, T., Monzani, M. E., Morselli, A., Moskalenko, I. V., Negro, M., Nuss, E., Ojha, R., Omodei, N., Orienti, M., Orlando, E., Palatiello, M., Paliya, V. S., Paneque, D., Perkins, J. S., Persic, M., Pesce-Rollins, M., Petrosian, V., Piron, F., Porter, T. A., Principe, G., Raino, S., Rando, R., Rani, B., Razzano, M., Razzaque, S., Reimer, A., Reimer, O., Reposeur, T., Sgro, C., Siskind, E. J., Spandre, G., Spinelli, P., Suson, D. J., Tajima, H., Thayer, J. B., Thompson, D. J., Torres, D. F., Tosti, G., Troja, E., Valverde, J., Vianello, G., Vogel, M., Wood, K., Yassine, M., Collaboration, HAWC, Alfaro, R., Alvarez, C., Alvarez, J. D., Arceo, R., Arteaga-Velazquez, J. C., Rojas, D. Avila, Solares, H. A. Ayala, Becerril, A., Belmont-Moreno, E., BenZvi, S. Y., Bernal, A., Braun, J., Brisbois, C., Caballero-Mora, K. S., Capistran, T., Carraminana, A., Casanova, S., Castillo, M., Cotti, U., Cotzomi, J., de Leon, S. Coutino, 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., Munoz, A. Gonzalez, 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., Vargas, H. Leon, 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, I., Tibolla, O., Tollefson, K., Torres, I., Ukwatta, T. N., Villasenor, L., Weisgarber, T., Westerhoff, S., Wisher, I. G., Wood, J., Yapici, T., Yodh, G., Zepeda, A., and Zhou, H.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The HAWC (High Altitude Water Cherenkov) 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, there are nineteen sources that are not associated with previously known TeV sources. We have studied fourteen 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 fourteen new HAWC sources from our analysis of Fermi-LAT data for energies higher than 10 GeV. During the search, we detected 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., Comment: Accepted for publication in the ApJ, Corresponding author: Nahee Park (VERITAS Collaboration), John W. Hewitt (Fermi-LAT Collaboration), Ignacio Taboada (HAWC Collaboration), 30 pages, 12 figures
Published: 2018
Full Text: View/download PDF

8. Measurement of Cosmic-ray Electrons at TeV Energies by VERITAS

Author: VERITAS Collaboration, Archer, A., Benbow, W., Bird, R., Brose, R., Buchovecky, M., Buckley, J. H., Bugaev, V., Connolly, M. P., Cui, W., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gillanders, G., Hütten, 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., O'Brien, S., Ong, R. A., Otte, A. N., Petrashyk, A., Pohl, M., Pueschel, E., 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., Tyler, J., Wakely, S. P., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Williamson, T. J, and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: 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, USA, 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 $\pm$ 40$_{stat}$ $\pm$ 140$_{syst}$ GeV., Comment: 17 pages, 2 figures, accepted for publication in PRD
Published: 2018
Full Text: View/download PDF

9. The extreme HBL behaviour of Markarian 501 during 2012

Author: Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Arcaro, C., Babić, A., Banerjee, B., Bangale, P., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Bernardini, E., Berti, A., Bhattacharyya, W., Blanch, O., Bonnoli, G., Carosi, R., Carosi, A., Chatterjee, A., Colak, S. M., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Cumani, P., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Di Pierro, F., Doert, M., Domínguez, A., Prester, D. Dominis, Doro, M., Glawion, D. Eisenacher, Engelkemeier, M., Ramazani, V. Fallah, Fernández-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Fruck, C., Galindo, D., López, R. J. García, Garczarczyk, M., Gaug, M., Giammaria, P., Godinović, N., Gora, D., Guberman, D., Hadasch, D., Hahn, A., Hassan, T., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Ishio, K., Konno, Y., Kubo, H., Kushida, J., Kuveždić, D., Lelas, D., Lindfors, E., Lombardi, S., Longo, F., López, M., Maggio, C., Majumdar, P., Makariev, M., Maneva, G., Manganaro, M., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Minev, M., Miranda, J. M., Mirzoyan, R., Moralejo, A., Moreno, V., Moretti, E., Nagayoshi, T., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nigro, C., Nilsson, K., Ninci, D., Nishijima, K., Noda, K., Nogués, L., Paiano, S., Palacio, J., Paneque, D., Paoletti, R., Paredes, J. M., Pedaletti, G., Peresano, M., Perri, L., Persic, M., Moroni, P. G. Prada, Prandini, E., Puljak, I., Garcia, J. R., Reichardt, I., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saito, T., Satalecka, K., Schroeder, S., Schweizer, T., Shore, S. N., Sitarek, J., Šnidarić, I., Sobczynska, D., Stamerra, A., Strzys, M., Surić, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Torres-Albà, N., Treves, A., Tsujimoto, S., Vanzo, G., Acosta, M. Vazquez, Vovk, I., Ward, J. E., Will, M., Zarić, D., Arbet-Engels, A., Baack, D., Balbo, M., Biland, A., Blank, M., Bretz, T., Bruegge, K., Bulinski, M., Buss, J., Dmytriiev, A., Dorner, D., Einecke, S., Elsaesser, D., Herbst, T., Hildebrand, D., Kortmann, L., Linhoff, L., Mahlke, M., Mannheim, K., Mueller, S. A., Neise, D., Neronov, A., Noethe, M., Oberkirch, J., Paravac, A., Rhode, W., Schleicher, B., Schulz, F., Sedlaczek, K., Shukla, A., Sliusar, V., Walter, R., Archer, A., Benbow, W., Bird, R., Brose, R., Buckley, J. H., Bugaev, V., Christiansen, J. L., Cui, W., Daniel, M. K., Falcone, A., Feng, Q., Finley, J. P., Gillanders, G. H., Gueta, O., Hanna, D., Hervet, O., Holder, J., Hughes, G., Hütten, M., 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., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pichel, A., Pohl, M., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Sushch, I., Tyler, J., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhel, A., Williams, D. A., Williamson, T. J, Zitzer, B., Perri, M., Verrecchia, F., Leto, C., Villata, M., Raiteri, C. M., Jorstad, S. G., Larionov, V. M., Blinov, D. A., Grishina, T. S., Kopatskaya, E. N., Larionova, E. G., Nikiforova, A. A., Morozova, D. A., Troitskaya, Yu. V., Troitsky, I. S., Kurtanidze, O. M., Nikolashvili, M. G., Kurtanidze, S. O., Kimeridze, G. N., Chigladze, R. A., Strigachev, A., Sadun, A. C., Moody, J. W., Chen, W. P., Lin, H. C., Acosta-Pulido, J. A., Arévalo, M. J., Carnerero, M. I., González-Morales, P. A., Manilla-Robles, A., Jermak, H., Steele, I., Mundel, C., Benítez, E., Hiriart, D., Smith, P. S., Max-Moerbeck, W., Readhead, A. C. S., Richards, J. L., Hovatta, T., Lähteenmäki, A., Tornikoski, M., Tammi, J., Georganopoulos, M., and Baring, M. G.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: A multiwavelength campaign was organized to take place between March and July of 2012. Excellent temporal coverage was obtained with more than 25 instruments, including the MAGIC, FACT and VERITAS Cherenkov telescopes, the instruments on board the Swift and Fermi spacecraft, and the telescopes operated by the GASP-WEBT collaboration. Mrk 501 showed a very high energy (VHE) gamma-ray flux above 0.2 TeV of $\sim$0.5 times the Crab Nebula flux (CU) for most of the campaign. The highest activity occurred on 2012 June 9, when the VHE flux was $\sim$3 CU, and the peak of the high-energy spectral component was found to be at $\sim$2 TeV. This study reports very hard X-ray spectra, and the hardest VHE spectra measured to date for Mrk 501. The fractional variability was found to increase with energy, with the highest variability occurring at VHE, and a significant correlation between the X-ray and VHE bands. The unprecedentedly hard X-ray and VHE spectra measured imply that their low- and high-energy components peaked above 5 keV and 0.5 TeV, respectively, during a large fraction of the observing campaign, and hence that Mrk 501 behaved like an extreme high-frequency- peaked blazar (EHBL) throughout the 2012 observing season. This suggests that being an EHBL may not be a permanent characteristic of a blazar, but rather a state which may change over time. The one-zone synchrotron self-Compton (SSC) scenario can successfully describe the segments of the SED where most energy is emitted, with a significant correlation between the electron energy density and the VHE gamma-ray activity, suggesting that most of the variability may be explained by the injection of high-energy electrons. The one-zone SSC scenario used reproduces the behaviour seen between the measured X-ray and VHE gamma-ray fluxes, and predicts that the correlation becomes stronger with increasing energy of the X-rays., Comment: 25 pages, 9 figures, accepted for publication in A&A. Corresponding authors: Gareth Hughes (gareth.hughes@cfa.harvard.edu), David Paneque (dpaneque@mppmu.mpg.de), Amit Shukla (amit.shukla@astro.uni-wuerzburg.de)
Published: 2018
Full Text: View/download PDF

10. Measurement of the Iron Spectrum in Cosmic Rays by VERITAS

Author: The VERITAS collaboration, Archer, A., Benbow, W., Bird, R., Brose, R., 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., Hütten, 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., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pohl, M., Popkow, A., Pueschel, E., 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, A., Williams, D. A., Wissel, S. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present a new measurement of the energy spectrum of iron nuclei in cosmic rays from 20 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 $\frac{\mathrm{d} F}{\mathrm{d} E}=f_0\cdot \left(\frac{E}{E_0}\right)^{-\gamma}$ over the full energy range, with $\gamma = 2.82 \pm 0.30 \mathrm{(stat.)} ^{+0.24}_{-0.27} \mathrm{(syst.)}$ and $f_0 = \left( 4.82 \pm 0.98 \mathrm{(stat.)}^{+2.12}_{-2.70} \mathrm{(syst.)} \right)\cdot 10^{-7}$m$^{-2}$s$^{-1}$sr$^{-1}$TeV$^{-1}$ 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., Comment: 16 pages, 5 figures, submitted to Phys. Rev. D
Published: 2018
Full Text: View/download PDF

11. VERITAS observations of the BL Lac object TXS 0506+056

Author: Abeysekara, A. U., Archer, A., Benbow, W., Bird, R., Brill, A., Brose, R., Buckley, J. H., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gillanders, G. H., Gueta, O., 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., Lang, M. J., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rulten, C., Sadeh, I., Santander, M., Scott, S. S., Sembroski, G. H., Shahinyan, K., Tyler, J., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Williamson, T. J, and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: On 2017 September 22, the IceCube Neutrino Observatory reported the detection of the high-energy neutrino event \icnu, of potential astrophysical origin. It was soon determined that the neutrino direction was consistent with the location of the gamma-ray blazar \txs~(3FGL J0509.4+0541), which was in an elevated gamma-ray emission state as measured by the \emph{Fermi} satellite. VERITAS observations of the neutrino/blazar region started on 2017 September 23 in response to the neutrino alert and continued through 2018 February 6. While no significant very-high-energy (VHE; E $>$ 100 GeV) emission was observed from the blazar by VERITAS in the two-week period immediately following the IceCube alert, TXS 0506+056 was detected by VERITAS with a significance of 5.8 standard deviations ($\sigma$) in the full 35-hour data set. The average photon flux of the source during this period was $(8.9 \pm 1.6) \times 10^{-12} \; \mathrm{cm}^{-2} \, \mathrm{s}^{-1}$, or 1.6\% of the Crab Nebula flux, above an energy threshold of 110 GeV, with a soft spectral index of $4.8 \pm 1.3$.
Published: 2018
Full Text: View/download PDF

12. A Very High Energy $\gamma$-Ray Survey towards the Cygnus Region of the Galaxy

Author: The VERITAS Collaboration, Abeysekara, A. U., Archer, A., Aune, T., Benbow, W., Bird, R., Brose, R., Buchovecky, M., Bugaev, V., Cui, W., Daniel, M. K., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Flinders, A., Fortson, L., Furniss, A., Gotthelf, E. V., Grube, J., Hanna, D., Hervet, O., Holder, J., Huang, K., Hughes, G., Humensky, T. B., Hütten, M., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Kumar, S., Lang, M. J., Lin, T. T. Y., Maier, G., McArthur, S., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Otte, A. N., Pandel, D., Park, N., Petrashyk, A., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rousselle, J., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Tyler, J., Vassiliev, V. V., Wakely, S. P., Ward, J. E., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present results from deep observations towards the Cygnus region using 300 hours of very-high-energy (VHE) $\gamma$-ray data taken with the VERITAS Cherenkov telescope array and over seven years of high-energy $\gamma$-ray data taken with the Fermi satellite at an energy above 1 GeV. As the brightest region of diffuse $\gamma$-ray emission in the northern sky, the Cygnus region provides a promising area to probe the origins of cosmic rays. We report the identification of a potential Fermi-LAT counterpart to VER J2031+415 (TeV J2032+4130), and resolve the extended VHE source VER J2019+368 into two source candidates (VER J2018+367* and VER J2020+368*) and characterize their energy spectra. The Fermi-LAT morphology of 3FGL 2021.0+4031e (the Gamma-Cygni supernova remnant) was examined and a region of enhanced emission coincident with VER J2019+407 was identified and jointly fit with the VERITAS data. By modeling 3FGL J2015.6+3709 as two sources, one located at the location of the pulsar wind nebula CTB 87 and one at the quasar QSO J2015+371, a continuous spectrum from 1 GeV to 10 TeV was extracted for VER J2016+371 (CTB 87). An additional 71 locations coincident with Fermi-LAT sources and other potential objects of interest were tested for VHE $\gamma$-ray emission, with no emission detected and upper limits on the differential flux placed at an average of 2.3% of the Crab Nebula ux. We interpret these observations in a multiwavelength context and present the most detailed $\gamma$-ray view of the region to date., Comment: 49 Pages, 22 Figures, 13 Tables, Accepted to ApJ
Published: 2018
Full Text: View/download PDF

13. A strong limit on the very-high-energy emission from GRB 150323A

Author: Abeysekara, A. U., Archer, A., Benbow, W., Bird, R., Brose, R., Buchovecky, M., Bugaev, V., Connolly, M. P., Cui, W., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Flinders, A., Fortson, L., Furniss, A., Gillanders, G. H., Hütten, 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., Lang, M. J., Lin, T. T. Y., Maier, G., McArthur, S., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Park, N., Perkins, J. S., Petrashyk, A., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Tyler, J., Wakely, S. P., Weiner, O. M., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Zitzer, B., Vurm, Indrek, and Beloborodov, Andrei
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: On 2015 March 23, VERITAS responded to a $Swift$-BAT detection of a gamma-ray burst, with observations beginning 270 seconds after the onset of BAT emission, and only 135 seconds after the main BAT emission peak. No statistically significant signal is detected above 140 GeV. The VERITAS upper limit on the fluence in a 40 minute integration corresponds to about 1% of the prompt fluence. Our limit is particularly significant since the very-high-energy (VHE) observation started only $\sim$2 minutes after the prompt emission peaked, and $Fermi$-LAT observations of numerous other bursts have revealed that the high-energy emission is typically delayed relative to the prompt radiation and lasts significantly longer. Also, the proximity of GRB~150323A ($z=0.593$) limits the attenuation by the extragalactic background light to $\sim 50$ % at 100-200 GeV. We conclude that GRB 150323A had an intrinsically very weak high-energy afterglow, or that the GeV spectrum had a turnover below $\sim100$ GeV. If the GRB exploded into the stellar wind of a massive progenitor, the VHE non-detection constrains the wind density parameter to be $A\gtrsim 3\times 10^{11}$ g cm$^{-1}$, consistent with a standard Wolf-Rayet progenitor. Alternatively, the VHE emission from the blast wave would be weak in a very tenuous medium such as the ISM, which therefore cannot be ruled out as the environment of GRB 150323A., Comment: 6 pages, 1 figure. Accepted for publication in The Astrophysical Journal
Published: 2018
Full Text: View/download PDF

14. Multiwavelength observations of the blazar BL Lacertae: a new fast TeV gamma-ray flare

Author: Abeysekara, A. U., Benbow, W., Bird, R., Brantseg, T., Brose, R., Buchovecky, M., Buckley, J. H., Bugaev, V., Connolly, M. P., Cui, W., Daniel, M. K., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gillanders, G. H., Gunawardhana, I., Hütten, M., Hanna, D., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kertzman, M., Krennrich, F., Lang, M. J., Lin, T. T. Y., McArthur, S., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Williams, D. A., Zitzer, B., Jorstad, S. G., Marscher, A. P., Lister, M. L., Kovalev, Y. Y., Pushkarev, A. B., Savolainen, T., Agudo, I., Molina, S. N., Gómez, J. L., Larionov, V. M., Borman, G. A., Mokrushina, A. A., Tornikoski, M., Lähteenmäki, A., Chamani, W., Enestam, S., Kiehlmann, S., Hovatta, T., Smith, P. S., and Pontrelli, P.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Combined with very-long-baseline interferometry measurements, the observations of fast TeV gamma-ray flares probe the structure and emission mechanism of blazar jets. However, only a handful of such flares have been detected to date, and only within the last few years have these flares been observed from lower-frequency-peaked BL~Lac objects and flat-spectrum radio quasars. We report on a fast TeV gamma-ray flare from the blazar BL~Lacertae observed by VERITAS, with a rise time of $\sim$2.3~hr and a decay time of $\sim$36~min. The peak flux above 200 GeV is $(4.2 \pm 0.6) \times 10^{-6} \;\text{photon} \;\text{m}^{-2}\; \text{s}^{-1}$ measured with a 4-minute-binned light curve, corresponding to $\sim$180\% of the flux which is observed from the Crab Nebula above the same energy threshold. Variability contemporaneous with the TeV gamma-ray flare was observed in GeV gamma-ray, X-ray, and optical flux, as well as in optical and radio polarization. Additionally, a possible moving emission feature with superluminal apparent velocity was identified in VLBA observations at 43 GHz, potentially passing the radio core of the jet around the time of the gamma-ray flare. We discuss the constraints on the size, Lorentz factor, and location of the emitting region of the flare, and the interpretations with several theoretical models which invoke relativistic plasma passing stationary shocks., Comment: 23 pages, 9 figures
Published: 2018
Full Text: View/download PDF

15. VERITAS contributions to the 35th International Cosmic Ray Conference

Author: Abeysekara, A. U., Archambault, S., Archer, A., Benbow, W., Bird, R., Brose, R., Buchovecky, M., Christiansen, J. L., Connolly, M. P., Cui, W., Daniel, M. K., Falcone, A., Feng, Q., Fernandez-Alonso, M., Finley, J. P., Fleischhack, H., Fortson, L., Furniss, A., Gillanders, G. H., Hütten, M., Hanna, D., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Maier, G., McArthur, S., Moriarty, P., Mukherjee, R., Nieto, D., O'Brien, S., Ong, R. A., Otte, A. N., Pandel, D., Park, N., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Roache, E., Rovero, A. C., Sadeh, I., Santander, M., Schlenstedt, S., Sembroski, G. H., Shahinyan, K., Tyler, J., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Williamson, T. J, and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Compilation of papers presented by the VERITAS Collaboration at the 35th International Cosmic Ray Conference (ICRC), held July 12 through July 20, 2017 in Busan, South Korea., Comment: html page. 2017 ICRC, Busan, South Korea. A full list of author affiliations can be found at this link: https://veritas.sao.arizona.edu/conferences/ICRC2017_AuthList.html
Published: 2017

16. Discovery of very-high-energy emission from RGB J2243+203 and derivation of its redshift upper limit

Author: Abeysekara, A. U., Archambault, S., Archer, A., Benbow, W., Bird, R., Brose, R., 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., Hutten, 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., OBrien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Poh, M., Popkow, A., Puesche, E., 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, I., Tyler, J., Vassiliev, V. V., Wakely, S. P., Weiner, O. M., Weinstein, A., Wilcox, P., Wilhelm, A., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Very-high-energy (VHE; $>$ 100 GeV) gamma-ray emission from the blazar RGB J2243+203 was discovered with the VERITAS Cherenkov telescope array, during the period between 21 and 24 December 2014. The VERITAS energy spectrum from this source can be fit by a power law with a photon index of $4.6 \pm 0.5$, and a flux normalization at 0.15 TeV of $(6.3 \pm 1.1) \times 10^{-10} ~ \textrm{cm}^{-2} \textrm{s}^{-1} \textrm{TeV}^{-1}$. The integrated \textit{Fermi}-LAT flux from 1 GeV to 100 GeV during the VERITAS detection is $(4.1 \pm 0.8) \times 10^{\textrm{-8}} ~\textrm{cm}^{\textrm{-2}}\textrm{s}^{\textrm{-1}}$, which is an order of magnitude larger than the four-year-averaged flux in the same energy range reported in the 3FGL catalog, ($4.0 \pm 0.1 \times 10^{\textrm{-9}} ~ \textrm{cm}^{\textrm{-2}}\textrm{s}^{\textrm{-1}}$). The detection with VERITAS triggered observations in the X-ray band with the \textit{Swift}-XRT. However, due to scheduling constraints \textit{Swift}-XRT observations were performed 67 hours after the VERITAS detection, not simultaneous with the VERITAS observations. The observed X-ray energy spectrum between 2 keV and 10 keV can be fitted with a power-law with a spectral index of $2.7 \pm 0.2$, and the integrated photon flux in the same energy band is $(3.6 \pm 0.6) \times 10^{-13} ~\textrm{cm}^{-2} \textrm{s}^{-1}$. EBL model-dependent upper limits of the blazar redshift have been derived. Depending on the EBL model used, the upper limit varies in the range from z $<~0.9$ to z $<~1.1$.
Published: 2017
Full Text: View/download PDF

17. Dark Matter Constraints from a Joint Analysis of Dwarf Spheroidal Galaxy Observations with VERITAS

Author: VERITAS Collaboration, Archambault, S., Archer, A., Benbow, W., Bird, R., Bourbeau, E., Brantseg, T., Buchovecky, M., Buckley, J. H., Bugaev, V., Byrum, K., Cerruti, M., Christiansen, J. L., Connolly, M. P., Cui, W., Daniel, M. K., Feng, Q., Finley, J. P., Fleischhack, H., Fortson, L., Furniss, A., Geringer-Sameth, A., Griffin, S., Grube, J., Hütten, M., Håkansson, N., Hanna, D., Hervet, O., Holder, J., Hughes, G., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Koushiappas, S., Krause, M., Kumar, S., Lang, M. J., Lin, T. T. Y., McArthur, S., Moriarty, P., Nieto, D., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Trépanier, S., Tucci, J. V., Tyler, J., Wakely, S. P., Weinstein, A., Wilcox, P., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present constraints on the annihilation cross section of WIMP dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of $\sim$230 hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is $1.35\times 10^{-23} {\mathrm{ cm^3s^{-1}}}$ at 1 TeV for the bottom quark ($b\bar{b}$) final state, $2.85\times 10^{-24}{\mathrm{ cm^3s^{-1}}}$ at 1 TeV for the tau lepton ($\tau^{+}\tau^{-}$) final state and $1.32\times 10^{-25}{\mathrm{ cm^3s^{-1}}}$ at 1 TeV for the gauge boson ($\gamma\gamma$) final state., Comment: 14 pages, 9 figures, published in PRD, Ascii tables containing annihilation cross sections limits are available for download as ancillary files with readme.txt file description of limits
Published: 2017
Full Text: View/download PDF

18. Gamma-ray Observations Under Bright Moonlight with VERITAS

Author: Archambault, S., Archer, A., Benbow, W., Bird, R., Bourbeau, E., Bouvier, A., Buchovecky, M., Bugaev, V., Cardenzana, J. V, Cerruti, M., Ciupik, L., Connolly, M. P., Cui, W., Daniel, M. K., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Fortson, L., Furniss, A., Gillanders, G. H., Griffin, S., Hanna, D., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Hütten, M., Johnson, C. A., Kaaret, P., Kar, P., Kertzman, M., Kieda, D., Krause, M., Lang, M. J., Maier, G., McArthur, S., Moriarty, P., Mukherjee, R., Nieto, D., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rulten, C., Sadeh, I., Sembroski, G. H., Shahinyan, K., Staszak, D., Telezhinsky, I., Trepanier, S., Wakely, S. P., Weinstein, A., Wilcox, P., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: Imaging atmospheric Cherenkov telescopes (IACTs) are equipped with sensitive photomultiplier tube (PMT) cameras. Exposure to high levels of background illumination degrades the efficiency of and potentially destroys these photo-detectors over time, so IACTs cannot be operated in the same configuration in the presence of bright moonlight as under dark skies. Since September 2012, observations have been carried out with the VERITAS IACTs under bright moonlight (defined as about three times the night-sky-background (NSB) of a dark extragalactic field, typically occurring when Moon illumination > 35%) in two observing modes, firstly by reducing the voltage applied to the PMTs and, secondly, with the addition of ultra-violet (UV) bandpass filters to the cameras. This has allowed observations at up to about 30 times previous NSB levels (around 80% Moon illumination), resulting in 30% more observing time between the two modes over the course of a year. These additional observations have already allowed for the detection of a flare from the 1ES 1727+502 and for an observing program targeting a measurement of the cosmic-ray positron fraction. We provide details of these new observing modes and their performance relative to the standard VERITAS observations.
Published: 2017
Full Text: View/download PDF

19. Multiwavelength follow-up of a rare IceCube neutrino multiplet

Author: Aartsen, M. G., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., Ahrens, M., Samarai, I. Al, Altmann, D., Andeen, K., Anderson, T., Ansseau, I., Anton, G., Archinger, M., Argüelles, C., Auffenberg, J., Axani, S., Bai, X., Barwick, S. W., Baum, V., Bay, R., Beatty, J. J., Tjus, J. Becker, Becker, K. -H., BenZvi, S., Berley, D., Bernardini, E., Bernhard, A., Besson, D. Z., Binder, G., Bindig, D., Blaufuss, E., Blot, S., Bohm, C., Börner, M., Bos, F., Bose, D., Böser, S., Botner, O., Braun, J., Brayeur, L., Bretz, H. -P., Bron, S., Burgman, A., Carver, T., Casier, M., Cheung, E., Chirkin, D., Christov, A., Clark, K., Classen, L., Coenders, S., Collin, G. H., Conrad, J. M., Cowen, D. F., Cross, R., Day, M., de, J. P. A. M., ré, De Clercq, C., Rosendo, E. del Pino, Dembinski, H., De Ridder, S., Desiati, P., de Vries, K. D., de Wasseige, G., de With, M., DeYoung, T., di Lorenzo, V., Dujmovic, H., Dumm, J. P., Dunkman, M., Eberhardt, B., Ehrhardt, T., Eichmann, B., Eller, P., Euler, S., Evenson, P. A., Fahey, S., Fazely, A. R., Feintzeig, J., Felde, J., Filimonov, K., Finley, C., Flis, S., Fösig, C. -C., Franckowiak, A., Friedman, E., Fuchs, T., Gaisser, T. K., Gallagher, J., Gerhardt, L., Ghorbani, K., Giang, W., Gladstone, L., Glauch, T., Glüsenkamp, T., Goldschmidt, A., Gonzalez, J. G., Grant, D., Griffith, Z., Haack, C., Hallgren, A., Halzen, F., Hansen, E., Hansmann, T., Hanson, K., Hebecker, D., Heereman, D., Helbing, K., Hellauer, R., Hickford, S., Hignight, J., Hill, G. C., Hoffman, K. D., Hoffmann, R., Hoshina, K., Huang, F., Huber, M., Hultqvist, K., In, S., Ishihara, A., Jacobi, E., Japaridze, G. S., Jeong, M., Jero, K., Jones, B. J. P., Kang, W., Kappes, A., Karg, T., Karle, A., Katz, U., Kauer, M., Keivani, A., Kelley, J. L., Kheirandish, A., Kim, J., Kim, M., Kintscher, T., Kiryluk, J., Kittler, T., Klein, S. R., Kohnen, G., Koirala, R., Kolanoski, H., Konietz, R., Köpke, L., Kopper, C., Kopper, S., Koskinen, D. J., Kowalski, M., Krings, K., Kroll, M., Krückl, G., Krüger, C., Kunnen, J., Kunwar, S., Kurahashi, N., Kuwabara, T., Kyriacou, A., Labare, M., Lanfranchi, J. L., Larson, M. J., Lauber, F., Lesiak-Bzdak, M., Leuermann, M., Lu, L., Lünemann, J., Madsen, J., Maggi, G., Mahn, K. B. M., Mancina, S., Mandelartz, M., Maruyama, R., Mase, K., Maunu, R., McNally, F., Meagher, K., Medici, M., Meier, M., Menne, T., Merino, G., Meures, T., Miarecki, S., Micallef, J., Momenté, G., Montaruli, T., Moulai, M., Nahnhauer, R., Naumann, U., Neer, G., Niederhausen, H., Nowicki, S. C., Nygren, D. R., Pollmann, A. Obertacke, Olivas, A., O'Murchadha, A., Palczewski, T., Pandya, H., Pankova, D. V., Peiffer, P., Penek, Ö., Pepper, J. A., Heros, C. Pérez de los, Pieloth, D., Pinat, E., Price, P. B., Przybylski, G. T., Quinnan, M., Raab, C., Rädel, L., Rameez, M., Rawlins, K., Reimann, R., Relethford, B., Relich, M., Resconi, E., Rhode, W., Richman, M., Riedel, B., Robertson, S., Rongen, M., Rott, C., Ruhe, T., Ryckbosch, D., Rysewyk, D., Sabbatini, L., Herrera, S. E. Sanchez, Sandrock, A., Sandroos, J., Sarkar, S., Satalecka, K., Schlunder, P., Schmidt, T., Schoenen, S., Schöneberg, S., Schumacher, L., Seckel, D., Seunarine, S., Soldin, D., Song, M., Spiczak, G. M., Spiering, C., Stachurska, J., Stanev, T., Stasik, A., Stettner, J., Steuer, A., Stezelberger, T., Stokstad, R. G., Stößl, A., Ström, R., Strotjohann, N. L., Sullivan, G. W., Sutherland, M., Taavola, H., Taboada, I., Tatar, J., Tenholt, F., Ter-Antonyan, S., Terliuk, A., Tešić, G., Tilav, S., Toale, P. A., Tobin, M. N., Toscano, S., Tosi, D., Tselengidou, M., Tung, C. F., Turcati, A., Unger, E., Usner, M., Vandenbroucke, J., van Eijndhoven, N., Vanheule, S., van Rossem, M., van Santen, J., Vehring, M., Voge, M., Vogel, E., Vraeghe, M., Walck, C., Wallace, A., Wallraff, M., Wandkowsky, N., Waza, A., Weaver, Ch., Weiss, M. J., Wendt, C., Westerhoff, S., Whelan, B. J., Wickmann, S., Wiebe, K., Wiebusch, C. H., Wille, L., Williams, D. R., Wills, L., Wolf, M., Wood, T. R., Woolsey, E., Woschnagg, K., Xu, D. L., Xu, X. W., Xu, Y., Yanez, J. P., Yodh, G., Yoshida, S., Zoll, M., Stanek, K. Z., Shappee, B. J., Kochanek, C. S., Holoien, T. W. -S., Prieto, J. L., Fox, D. B., DeLaunay, J. J., Turley, C. F., Barthelmy, S. D., Lien, A. Y., Mészáros, P., Murase, K., Kocevski, D., Buehler, R., Giomi, M., Racusin, J. L., Albert, A., Alfaro, R., Alvarez, C., Álvarez, J. D., Arceo, R., Arteaga-Velázquez, J. C., Solares, H. A. Ayala, Barber, A. S., Becerril, N. Baustista-Elivar A., Belmont-Moreno, E., Bernal, A., Brisbois, C., Caballero-Mora, K. S., Capistrán, T., Carramiñana, A., Casanova, S., Castillo, M., Cotti, U., de León, S. Coutiño, de la Fuente, E., De León, C., Hernandez, R. Diaz, Díaz-Vélez, J. C., Dingus, B. L., DuVernois, M. A., Ellsworth, R. W., Engel, K., Fiorino, D. W., Fraija, N., García-González, J. A., Gerhardt, M., Muñoz, A. González, González, M. M., Goodman, J. A., Hampel-Arias, Z., Harding, J. P., Hernandez, S., Hui, C. M., Hüntemeyer, P., Iriarte, A., Jardin-Blicq, A., Joshi, V., Kaufmann, S., Lara, A., Lauer, R. J., Lee, W. H., Lennarz, D., Vargas, H. León, Linnemann, J. T., Raya, G. Luis, Luna-García, R., López-Coto, R., Malone, K., Marinelli, S. S., Martinez, O., Martinez-Castellanos, I., Martínez-Castro, J., Martínez-Huerta, H., Matthews, J. A., Miranda-Romagnoli, P., Moreno, E., Mostafá, M., Nellen, L., Newbold, M., Nisa, M. U., Noriega-Papaqui, R., Pelayo, R., Pretz, J., Pérez-Pérez, E. G., Ren, Z., Rho, C. D., Rivière, C., Rosa-González, D., Rosenberg, M., Greus, F. Salesa, Sandoval, A., Schneider, M., Schoorlemmer, H., Sinnis, G., Smith, A. J., Springer, R. W., Surajbali, P., Tibolla, O., Tollefson, K., Torres, I., Ukwatta, T. N., Villaseñor, L., Weisgarber, T., Wisher, I. G., Wood, J., Yapici, T., Zepeda, A., Zhou, H., Arcavi, I., Hosseinzadeh, G., Howell, D. A., Valenti, S., McCully, C., Lipunov, V. M., Gorbovskoy, E. S., Tiurina, N. V., Balanutsa, P. V., Kuznetsov, A. S., Kornilov, V. G., Chazov, V., Budnev, N. M., Gress, O. A., Ivanov, K. I., Tlatov, A. G., Lopez, R. Rebolo, Serra-Ricart, M., Evans, P. A., Kennea, J. A., Gehrels, N., Osborne, J. P., Page, K. L., Abeysekara, A. U., Archer, A., Benbow, W., Bird, R., Brantseg, T., Bugaev, V., Cardenzana, J. V, Connolly, M. P., Cui, W., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Fortson, L., Furniss, A., Griffin, S., Grube, J., Hütten, M., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Krause, M., Kumar, S., Lang, M. J., Lin, T. T. Y., McArthur, S., Moriarty, P., Mukherjee, R., Nieto, D., Ong, R. A., Otte, A. N., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Staszak, D., Trépanier, S., Tyler, J., Wakely, S. P., Weinstein, A., Wilcox, P., Wilhelm, A., Williams, D. A., Zitzer, B., Bellm, E., Cano, Z., Gal-Yam, A., Kann, D. A., Ofek, E. O., Rigault, M., and Soumagnac, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: On February 17 2016, the IceCube real-time neutrino search identified, for the first time, three muon neutrino candidates arriving within 100 s of one another, consistent with coming from the same point in the sky. Such a triplet is expected once every 13.7 years as a random coincidence of background events. However, considering the lifetime of the follow-up program the probability of detecting at least one triplet from atmospheric background is 32%. Follow-up observatories were notified in order to search for an electromagnetic counterpart. Observations were obtained by Swift's X-ray telescope, by ASAS-SN, LCO and MASTER at optical wavelengths, and by VERITAS in the very-high-energy gamma-ray regime. Moreover, the Swift BAT serendipitously observed the location 100 s after the first neutrino was detected, and data from the Fermi LAT and HAWC observatory were analyzed. We present details of the neutrino triplet and the follow-up observations. No likely electromagnetic counterpart was detected, and we discuss the implications of these constraints on candidate neutrino sources such as gamma-ray bursts, core-collapse supernovae and active galactic nucleus flares. This study illustrates the potential of and challenges for future follow-up campaigns., Comment: 23 pages, 13 figures, accepted by A&A on July 30 2017
Published: 2017
Full Text: View/download PDF

20. Gamma-ray observations of Tycho's SNR with VERITAS and Fermi

Author: VERITAS Collaboration, Archambault, S., Archer, A., Benbow, W., Bird, R., Bourbeau, E., Buchovecky, M., Buckley, J. H., Bugaev, V., Cerruti, M., Connolly, M. P., Cui, W., Dwarkadas, V. V., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Fortson, L., Furniss, A., Griffin, S., Hutten, M., Hanna, D., Holder, J., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Kumar, S., Lang, M. J., Maier, G., McArthur, S., McCann, A., Moriarty, P., Mukherjee, R., Nieto, D., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Slane, P., Staszak, D., Telezhinsky, I., Trepanier, S., Tyler, J., Wakely, S. P., Weinstein, A., Weisgarber, T., Wilcox, P., Wilhelm, A., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: High-energy gamma-ray emission from supernova remnants (SNRs) has provided a unique perspective for studies of Galactic cosmic-ray acceleration. Tycho's SNR is a particularly good target because it is a young, type Ia SNR that is well-studied over a wide range of energies and located in a relatively clean environment. Since the detection of gamma-ray emission from Tycho's SNR by VERITAS and Fermi-LAT, there have been several theoretical models proposed to explain its broadband emission and high-energy morphology. We report on an update to the gamma-ray measurements of Tycho's SNR with 147 hours of VERITAS and 84 months of Fermi-LAT observations, which represents about a factor of two increase in exposure over previously published data. About half of the VERITAS data benefited from a camera upgrade, which has made it possible to extend the TeV measurements toward lower energies. The TeV spectral index measured by VERITAS is consistent with previous results, but the expanded energy range softens a straight power-law fit. At energies higher than 400 GeV, the power-law index is $2.92 \pm 0.42_{\mathrm{stat}} \pm 0.20_{\mathrm{sys}}$. It is also softer than the spectral index in the GeV energy range, $2.14 \pm 0.09_{\mathrm{stat}} \pm 0.02_{\mathrm{sys}}$, measured by this study using Fermi--LAT data. The centroid position of the gamma-ray emission is coincident with the center of the remnant, as well as with the centroid measurement of Fermi--LAT above 1 GeV. The results are consistent with an SNR shell origin of the emission, as many models assume. The updated spectrum points to a lower maximum particle energy than has been suggested previously., Comment: Accepted for publication in The Astrophysical Journal
Published: 2017
Full Text: View/download PDF

21. Search for Magnetically Broadened Cascade Emission From Blazars with VERITAS

Author: VERITAS Collaboration, Archambault, S., Archer, A., Benbow, W., Buchovecky, M., Bugaev, V., Cerruti, M., Connolly, M. P., Cui, W., Falcone, A., Alonso, M. Fernández, Finley, J. P., Fleischhack, H., Fortson, L., Furniss, A., Griffin, S., Hütten, M., Hervet, O., Holder, J., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kieda, D., Krause, M., Krennrich, F., Lang, M. J., Lin, T. T. Y., Maier, G., McArthur, S., Moriarty, P., Nieto, D., O'Brien, S., Ong, R. A., Otte, A. N., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Sadeh, I., Shahinyan, K., Staszak, D., Telezhinsky, I., Tyler, J., Wakely, S. P., Weinstein, A., Weisgarber, T., Wilcox, P., Wilhelm, A., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present a search for magnetically broadened gamma-ray emission around active galactic nuclei (AGN), using VERITAS observations of seven hard-spectrum blazars. A cascade process occurs when multi-TeV gamma rays from AGN interact with extragalactic background light (EBL) photons to produce electron-positron pairs, which then interact with cosmic microwave background (CMB) photons via inverse-Compton scattering to produce gamma rays. Due to the deflection of the electron-positron pairs, a non-zero intergalactic magnetic field (IGMF) would potentially produce detectable effects on the angular distribution of the cascade emission. In particular, an angular broadening compared to the unscattered emission could occur. Through non-detection of angularly broadened emission from 1ES 1218+304, the source with the largest predicted cascade fraction, we exclude a range of IGMF strengths around $10^{-14}$G at the 95% confidence level. The extent of the exclusion range varies with the assumptions made about the intrinsic spectrum of 1ES 1218+304 and the EBL model used in the simulation of the cascade process. All of the sources are used to set limits on the flux due to extended emission., Comment: Accepted for publication in The Astrophysical Journal
Published: 2017
Full Text: View/download PDF

22. Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009

Author: Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Banerjee, B., Bangale, P., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Bernardini, E., Berti, A., Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Buson, S., Carosi, A., Chatterjee, A., Clavero, R., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Wilhelmi, E. de Ona, Di Pierro, F., Doert, M., Domínguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Glawion, D. Eisenacher, Elsaesser, D., Engelkemeier, M., Ramazani, V. Fallah, Fernández-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., Galindo, D., López, R. J. García, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Giammaria, P., Godinović, N., Munoz, A. González, Gora, D., Guberman, D., Hadasch, D., Hahn, A., Hanabata, Y., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Hughes, G., Idec, W., Kodani, K., Konno, Y., Kubo, H., Kushida, J., La Barbera, A., Lelas, D., Lindfors, E., Lombardi, S., Longo, F., López, M., López-Coto, R., Majumdar, P., Makariev, M., Mallot, K., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Miranda, J. M., Mirzoyan, R., Moralejo, A., Moretti, E., Nakajima, D., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nilsson, K., Nishijima, K., Noda, K., Nogués, L., Overkemping, A., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Pedaletti, G., Peresano, M., Perri, L., Persic, M., Poutanen, J., Moroni, P. G. Prada, Prandini, E., Puljak, I., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Garcia, J. Rodriguez, Saito, T., Satalecka, K., Schröder, S., Schultz, C., Schweizer, T., Shore, S. N., Sillanpää, A., Sitarek, J., Snidaric, I., Sobczynska, D., Stamerra, A., Steinbring, T., Strzys, M., Surić, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thaele, J., Torres, D. F., Toyama, T., Treves, A., Vanzo, G., Verguilov, V., Vovk, I., Ward, J. E., Will, M., Wu, M. H., Zanin, R., Abeysekara, A. U., Archambault, S., Archer, A., Benbow, W., Bird, R., Buchovecky, M., Buckley, J. H., Bugaev, V., Connolly, M. P., Cui, W., Dickinson, H. J., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Flinders, A., Fortson, L., Gillanders, G. H., Griffin, S., Grube, J., Hütten, M., Hanna, D., Holder, J., Humensky, T. B., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Lang, M. J., Maier, G., McCann, A., Moriarty, P., Mukherjee, R., Nieto, D., O'Brien, S., Ong, R. A., Otte, N., Park, N., Perkins, J., Pichel, A., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Rulten, C., Sadeh, I., Santander, M., Sembroski, G. H., Shahinyan, K., Telezhinsky, I., Tucci, J. V., Tyler, J., Wakely, S. P., Weinstein, A., Wilcox, P., Wilhelm, A., Williams, D. A., Zitzer, B., Razzaque, S., Villata, M., Raiteri, C. M., Aller, H. D., Aller, M. F., Larionov, V. M., Arkharov, A. A., Blinov, D. A., Efimova, N. V., Grishina, T. S., Hagen-Thorn, V. A., Kopatskaya, E. N., Larionova, L. V., Larionova, E. G., Morozova, D. A., Troitsky, I. S., Ligustri, R., Calcidese, P., Berdyugin, A., Kurtanidze, O. M., Nikolashvili, M. G., Kimeridze, G. N., Sigua, L. A., Kurtanidze, S. O., Chigladze, R. A., Chen, W. P., Koptelova, E., Sakamoto, T., Sadun, A. C., Moody, J. W., Pace, C., Pearson III, R., Yatsu, Y., Mori, Y., Carraminyana, A., Carrasco, L., de la Fuente, E., Norris, J. P., Smith, P. S., Wehrle, A., Gurwell, M. A., Zook, Alma, Pagani, C., Perri, M., Capalbi, M., Cesarini, A., Krimm, H. A., Kovalev, Y. Y., Kovalev, Yu. A., Ros, E., Pushkarev, A. B., Lister, M. L., Sokolovsky, K. V., Kadler, M., Piner, G., Lähteenmäki, A., Tornikoski, M., Angelakis, E., Krichbaum, T. P., Nestoras, I., Fuhrmann, L, Zensus, J. A., Cassaro, P., Orlati, A., Maccaferri, G., Leto, P., Giroletti, M., Richards, J. L., Max-Moerbeck, W., and Readhead, A. C. S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1 which includes, among other instruments, MAGIC, VERITAS, Whipple 10-m, Fermi-LAT, RXTE, Swift, GASP-WEBT and VLBA. We find an increase in the fractional variability with energy, while no significant interband correlations of flux changes are found in the acquired data set. The higher variability in the very high energy (>100 GeV, VHE) gamma-ray emission and the lack of correlation with the X-ray emission indicate that the highest-energy electrons that are responsible for the VHE gamma-rays do not make a dominant contribution to the ~1 keV emission. Alternatively, there could be a very variable component contributing to the VHE gamma-ray emission in addition to that coming from the synchrotron self-Compton (SSC) scenarios. The space of SSC model parameters is probed following a dedicated grid-scan strategy, allowing for a wide range of models to be tested and offering a study of the degeneracy of model-to-data agreement in the individual model parameters. We find that there is some degeneracy in both the one-zone and the two-zone SSC scenarios that were probed, with several combinations of model parameters yielding a similar model-to-data agreement, and some parameters better constrained than others. The SSC model grid-scan shows that the flaring activity around 2009 May 22 cannot be modeled adequately with a one-zone SSC scenario, while it can be suitably described within a two-independent-zone SSC scenario. The observation of an electric vector polarization angle rotation coincident with the gamma-ray flare from 2009 May 1 resembles those reported previously for low frequency peaked blazars, hence suggesting that there are many similarities in the flaring mechanisms of blazars with different jet properties., Comment: 33 pages, 15 figures, accepted for publication in A&A. Corresponding authors: Marlene Doert (marlene.doert@tu-dortmund.de) and David Paneque (dpaneque@mppmu.mpg.de)
Published: 2016
Full Text: View/download PDF

23. Very High-Energy Gamma-Ray Follow-Up Program Using Neutrino Triggers from IceCube

Author: IceCube Collaboration, Aartsen, M. G., Abraham, K., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., Ahrens, M., Altmann, D., Andeen, K., Anderson, T., Ansseau, I., Anton, G., Archinger, M., Arguelles, C., Auffenberg, J., Axani, S., Bai, X., Barwick, S. W., Baum, V., Bay, R., Beatty, J. J., Becker-Tjus, J., Becker, K. -H., BenZvi, S., Berley, D., Bernardini, E., Bernhard, A., Besson, D. Z., Binder, G., Bindig, D., Bissok, M., Blaufuss, E., Blot, S., Bohm, C., Borner, M., Bos, F., Bose, D., Boser, S., Botner, O., Braun, J., Brayeur, L., Bretz, H. -P., Bron, S., Burgman, A., Carver, T., Casier, M., Cheung, E., Chirkin, D., Christov, A., Clark, K., Classen, L., Coenders, S., Collin, G. H., Conrad, J. M., Cross, D. F. Cowen R., Day, M., de Andre, J. P. A. M., De Clercq, C., Rosendo, E. del Pino, Dembinski, H., De Ridder, S., Desiati, P., de Vries, K. D., de Wasseige, G., de With, M., DeYoung, T., Diaz-Velez, J. C., di Lorenzo, V., Dujmovic, H., Dumm, J. P., Dunkman, M., Eberhardt, B., Ehrhardt, T., Eichmann, B., Eller, P., Euler, S., Evenson, P. A., Fahey, S., Fazely, A. R., Feintzeig, J., Felde, J., Filimonov, K., Finley, C., Flis, S., Fosig, C. -C., Franckowiak, A., Franke, R., Friedman, E., Fuchs, T., Gaisser, T. K., Gallagher, J., Gerhardt, L., Ghorbani, K., Giang, W., Gladstone, L., Glauch, T., Glusenkamp, T., Goldschmidt, A., Golup, G., Gonzalez, J. G., Grant, D., Griffith, Z., Haack, C., Ismail, A. Haj, Hallgren, A., Halzen, F., Hansen, E., Hansmann, T., Hanson, K., Hebecker, D., Heereman, D., Helbing, K., Hellauer, R., Hickford, S., Hignight, J., Hill, G. C., Hoffman, K. D., Hoffmann, R., Holzapfel, K., Hoshina, K., Huang, F., Huber, M., Hultqvist, K., In, S., Ishihara, A., Jacobi, E., Japaridze, G. S., Jeong, M., Jero, K., Jones, B. J. P., Jurkovic, M., Kappes, A., Karg, T., Karle, A., Katz, U., Kauer, M., Keivani, A., Kelley, J. L., Kheirandish, A., Kim, M., Kintscher, T., Kiryluk, J., Kittler, T., Klein, S. R., Kohnen, G., Koirala, R., Kolanoski, H., Konietz, R., Kopke, L., Kopper, C., Kopper, S., Koskinen, D. J., Kowalski, M., Krings, K., Kroll, M., Kruckl, G., Kruger, C., Kunnen, J., Kunwar, S., Kurahashi, N., Kuwabara, T., Labare, M., Lanfranchi, J. L., Larson, M. J., Lauber, F., Lennarz, D., Lesiak-Bzdak, M., Leuermann, M., Lu, L., Lunemann, J., Madsen, J., Maggi, G., Mahn, K. B. M., Mancina, S., Mandelartz, M., Maruyama, R., Mase, K., Maunu, R., McNally, F., Meagher, K., Medici, M., Meier, M., Meli, A., Menne, T., Merino, G., Meures, T., Miarecki, S., Mohrmann, L., Montaruli, T., Moulai, M., Nahnhauer, R., Naumann, U., Neer, G., Niederhausen, H., Nowicki, S. C., Nygren, D. R., Pollmann, A. Obertacke, Olivas, A., O'Murchadha, A., Palczewski, T., Pandya, H., Pankova, D. V., Peiffer, P., Penek, O., Pepper, J. A., Heros, C. Perez de los, Pieloth, D., Pinat, E., Price, P. B., Przybylski, G. T., Quinnan, M., Raab, C., Radel, L., Rameez, M., Rawlins, K., Reimann, R., Relethford, B., Relich, M., Resconi, E., Rhode, W., Richman, M., Riedel, B., Robertson, S., Rongen, M., Rott, C., Ruhe, T., Ryckbosch, D., Rysewyk, D., Sabbatini, L., Sanchez-Herrera, S. E., Sandrock, A., Sandroos, J., Sarkar, S., Satalecka, K., Schlunder, P., Schmidt, T., Schoenen, S., Schoneberg, S., Schumacher, L., Seckel, D., Seunarine, S., Soldin, D., Song, M., Spiczak, G. M., Spiering, C., Stanev, T., Stasik, A., Stettner, J., Steuer, A., Stezelberger, T., Stokstad, R. G., Stossl, A., Strom, R., Strotjohann, N. L., Sullivan, G. W., Sutherland, M., Taavola, H., Taboada, I., Tatar, J., Tenholt, F., Ter-Antonyan, S., Terliuk, A., Tevsic, G., Tilav, S., Toale, P. A., Tobin, M. N., Toscano, S., Tosi, D., Tselengidou, M., Turcati, A., Unger, E., Usner, M., Vandenbroucke, J., van Eijndhoven, N., Vanheule, S., van Rossem, M., van Santen, J., Veenkamp, J., Vehring, M., Voge, M., Vogel, E., Vraeghe, M., Walck, C., Wallace, A., Wallraff, M., Wandkowsky, N., Weaver, Ch., Weiss, M. J., Wendt, C., Westerhoff, S., Whelan, B. J., Wickmann, S., Wiebe, K., Wiebusch, C. H., Wille, L., Williams, D. R., Wills, L., Wolf, M., Wood, T. R., Woolsey, E., Woschnagg, K., Xu, D. L., Xu, X. W., Xu, Y., Yanez, J. P., Yodh, G., Yoshida, S., Collaboration, M. Zoll MAGIC, Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Banerjee, B., Bangale, P., de Almeida, U. Barres, Barrio, J. A., Gonzalez, J. Becerra, Bednarek, W., Berti, A., Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Buson, S., Carosi, A., Chatterjee, A., Clavero, R., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Wilhelmi, E. de Ona, Di Pierro, F., Doert, M., Dominguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Glawion, D. Eisenacher, Elsaesser, D., Engelkemeier, M., Ramazani, V. Fallah, Fernandez-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., Galindo, D., Lopez, R. J. Garcia, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Giammaria, P., Godinovic, N., Munoz, A. Gonzalez, Gora, D., Guberman, D., Hadasch, D., Hahn, A., Hanabata, Y., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Hughes, G., Idec, W., Kodani, K., Konno, Y., Kubo, H., Kushida, J., La Barbera, A., Lelas, D., Lindfors, E., Lombardi, S., Longo, F., Lopez, M., Lopez-Coto, R., Majumdar, P., Makariev, M., Mallot, K., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martinez, M., Mazin, D., Menzel, U., Miranda, J. M., Mirzoyan, R., Moralejo, A., Moretti, E., Nakajima, D., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nilsson, K., Nishijima, K., Noda, K., Nogues, L., Overkemping, A., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Pedaletti, G., Peresano, M., Perri, L., Persic, M., Poutanen, J., Moroni, P. G. Prada, Prandini, E., Puljak, I., Reichardt, I., Ribo, M., Rico, J., Garcia, J. Rodriguez, Saito, T., Schroeder, S., Schultz, C., Schweizer, T., Sillanpaa, A., Sitarek, J., Snidaric, I., Sobczynska, D., Stamerra, A., Steinbring, T., Strzys, M., Suric, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzic, T., Tescaro, D., Teshima, M., Thaele, J., Torres, D. F., Toyama, T., Treves, A., Vanzo, G., Verguilov, V., Vovk, I., Ward, J. E., Will, M., Wu, M. H., Collaboration, R. Zanin VERITAS, Abeysekara, A. U., Archambault, S., Archer, A., Benbow, W., Bird, R., Bourbeau, E., Buchovecky, M., Bugaev, V., Byrum, K., Cardenzana, J. V, Cerruti, M., Ciupik, L., Connolly, M. P., Cui, W., Dickinson, H. J., Dumm, J., Eisch, J. D., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Flinders, A., Fortson, L., Furniss, A., Gillanders, G. H., Griffin, S., Grube, J., Hutten, M., Haakansson, N., 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., McCann, A., Moriarty, P., Mukherjee, R., Nguyen, T., Nieto, D., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Pohl, M., Popkow, A., Pueschel, E., 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, I., Tucci, J. V., Tyler, J., Wakely, S. P., Weinstein, A., Wilcox, P., Wilhelm, A., Williams, D. A., and Zitzer, B.
Subjects: High Energy Physics - Experiment, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Instrumentation and Detectors
Abstract: We describe and report the status of a neutrino-triggered program in IceCube that generates real-time alerts for gamma-ray follow-up observations by atmospheric-Cherenkov telescopes (MAGIC and VERITAS). While IceCube is capable of monitoring the whole sky continuously, high-energy gamma-ray telescopes have restricted fields of view and in general are unlikely to be observing a potential neutrino-flaring source at the time such neutrinos are recorded. The use of neutrino-triggered alerts thus aims at increasing the availability of simultaneous multi-messenger data during potential neutrino flaring activity, which can increase the discovery potential and constrain the phenomenological interpretation of the high-energy emission of selected source classes (e.g. blazars). The requirements of a fast and stable online analysis of potential neutrino signals and its operation are presented, along with first results of the program operating between 14 March 2012 and 31 December 2015., Comment: accepted for publication in JINST
Published: 2016
Full Text: View/download PDF

24. A Search for Very High-Energy Gamma Rays from the Missing Link Binary Pulsar J1023+0038 with VERITAS

Author: Aliu, E., Archambault, S., Archer, A., Benbow, W., Bird, R., Biteau, J., Buchovecky, M., Buckley, J. H., Bugaev, V., Byrum, K., Cardenzana, J. V, Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Dickinson, H. 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., Hütten, M., Håkansson, N., Holder, J., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Lang, M. J., Loo, A., Maier, G., McArthur, S., McCann, A., Meagher, K., Moriarty, P., Mukherjee, R., Nguyen, T., Nieto, D., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Pandel, D., Park, N., Pelassa, V., Petrashyk, A., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rulten, C., Santander, M., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Varlotta, A., Vincent, S., Wakely, S. P., Weiner, O. M., Weinstein, A., Wilhelm, A., Williams, D. A., Zitzer, B., Chernyakova, M., and Roberts, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259--63/LS 2883, making it an ideal candidate for the study of high-energy non-thermal emission. It has been the subject of multi-wavelength campaigns following the disappearance of the pulsed radio emission in 2013 June, which revealed the appearance of an accretion disk around the neutron star. We present the results of very high-energy gamma-ray observations carried out by VERITAS before and after this change of state. Searches for steady and pulsed emission of both data sets yield no significant gamma-ray signal above 100 GeV, and upper limits are given for both a steady and pulsed gamma-ray flux. These upper limits are used to constrain the magnetic field strength in the shock region of the PSR J1023+0038 system. Assuming that very high-energy gamma rays are produced via an inverse-Compton mechanism in the shock region, we constrain the shock magnetic field to be greater than $\sim$2 G before the disappearance of the radio pulsar and greater than $\sim$10 G afterwards., Comment: 7 pages, 3 figures, accepted for publication in ApJ
Published: 2016
Full Text: View/download PDF

25. Discovery of Very High Energy Gamma Rays from 1ES 1440+122

Author: VERITAS Collaboration, Archambault, S., Archer, A., Barnacka, A., Behera, B., Beilicke, M., Benbow, W., Berger, K., Bird, R., Boettcher, M., Buckley, J. H., Bugaev, V., Cardenzana, J. V, Cerruti, M., Chen, X., Christiansen, J. L., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Cui, W., Dickinson, H. J., Dumm, J., Eisch, J. D., Errando, M., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fleischhack, H., Fortson, L., Furniss, A., Gillanders, G. H., Godambe, S., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Haakansson, N., Hanna, D., Holder, J., Hughes, G., Johnson, C. A., Kaaret, P., Kar, P., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Kumar, S., Lang, M. J., Madhavan, A. S, Maier, G., McArthur, S., McCann, A., Meagher, K., Millis, J., Moriarty, P., Nelson, T., Nieto, D., de Bhroithe, A. O'Faolain, Ong, R. A., Otte, A. N., Park, N., Perkins, J. S., Pohl, M., Popkow, A., Prokoph, H., Pueschel, E., Quinn, J., Ragan, K., Rajotte, J., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Sweeney, K, Telezhinsky, I., Tucci, J. V., Tyler, J., Varlotta, A., Vassiliev, V. V., Wakely, S. P., Welsing, R., Wilhelm, A., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The BL Lacertae object 1ES 1440+122 was observed in the energy range from 85 GeV to 30 TeV by the VERITAS array of imaging atmospheric Cherenkov telescopes. The observations, taken between 2008 May and 2010 June and totalling 53 hours, resulted in the discovery of $\gamma$-ray emission from the blazar, which has a redshift $z$=0.163. 1ES 1440+122 is detected at a statistical significance of 5.5 standard deviations above the background with an integral flux of (2.8$\pm0.7_{\mathrm{stat}}\pm0.8_{\mathrm{sys}}$) $\times$ 10$^{-12}$ cm$^{-2}$ s$^{-1}$ (1.2\% of the Crab Nebula's flux) above 200 GeV. The measured spectrum is described well by a power law from 0.2 TeV to 1.3 TeV with a photon index of 3.1 $\pm$ 0.4$_{\mathrm{stat}}$ $\pm$ 0.2$_{\mathrm{sys}}$. Quasi-simultaneous multi-wavelength data from the Fermi Large Area Telescope (0.3--300 GeV) and the Swift X-ray Telescope (0.2--10 keV) are additionally used to model the properties of the emission region. A synchrotron self-Compton model produces a good representation of the multi-wavelength data. Adding an external-Compton or a hadronic component also adequately describes the data., Comment: 8 pages, 4 figures. Accepted for publication in MNRAS
Published: 2016
Full Text: View/download PDF

26. Very High Energy outburst of Markarian 501 in May 2009

Author: Aliu, E., Archambault, S., Archer, A., Arlen, T., Aune, T., Barnacka, A., Behera, B., Beilicke, M., Benbow, W., Berger, K., Bird, R., Bouvier, A., Böttcher, M., Buchovecky, M., Buckley, J. H., Bugaev, V., Cardenzana, J. V, Cerruti, M., Cesarini, A., Chen, X., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Cui, W., Dumm, J., Eisch, J. D., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gall, D., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Hütten, M., Håkansson, N., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Khassen, Y., Kieda, D., Krause, M., Krawczynski, H., Krennrich, F., Lang, M. J., Madhavan, A. S, Maier, G., McArthur, S., McCann, A., Meagher, K., Millis, J., Moriarty, P., Mukherjee, R., Nieto, D., de Bhróithe, A. O'Faoláin, Ong, R. A., Orr, M., Otte, A. N., Pandel, D., Park, N., Pelassa, V., Perkins, J. S., Pichel, A., Pohl, M., Popkow, A., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Roache, E., Rousselle, J., Rovero, A. C., Saxon, D. B., Sembroski, G. H., Shahinyan, K., Sheidaei, F., Skole, C., Smith, A. W., Staszak, D., Telezhinsky, I., Theiling, M., Todd, N. W., Tucci, J. V., Tyler, J., Varlotta, A., Vassiliev, V. V., Vincent, S., Wakely, S. P., Weiner, O. M., Weinstein, A., Welsing, R., Wilhelm, A., Williams, D. A., Zitzer, B., Baring, M. G., Gónzalez, J. Becerra, Cillis, A. N., Horan, D., and Paneque, D.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The very high energy (VHE; E $>$ 100 GeV) blazar Markarian 501 was observed between April 17 and May 5 (MJD 54938--54956), 2009, as part of an extensive multi-wavelength campaign from radio to VHE. Strong VHE $\gamma$-ray activity was detected on May 1st with Whipple and VERITAS, when the flux (E $>$ 400 GeV) increased to 10 times the pre-flare baseline flux ($3.9{\times 10^{-11}}~{\rm ph~cm^{-2}~s^{-1}}$), reaching five times the flux of the Crab Nebula. This coincided with a decrease in the optical polarization and a rotation of the polarization angle by 15$^{\circ}$. This VHE flare showed a fast flux variation with an increase of a factor $\sim$4 in 25 minutes, and a falling time of $\sim$50 minutes. We present the observations of the quiescent state previous to the flare and of the high state after the flare, focusing on the flux and spectral variability from Whipple, VERITAS, Fermi-LAT, RXTE, and Swift combined with optical and radio data., Comment: 13 pages, 10 figures. Accepted for publication in Astronomy and Astrophysics
Published: 2016
Full Text: View/download PDF

27. VERITAS and Multiwavelength Observations of the BL Lacertae Object 1ES 1741+196

Author: VERITAS Collaboration, Abeysekara, A. U., Archambault, S., Archer, A., Benbow, W., Bird, R., Biteau, J., Buchovecky, M., Buckley, J. H., Bugaev, V., Byrum, K., Cardenzana, J. V, Cerruti, M., Chen, X., Christiansen, J. L., Ciupik, L., Connolly, M. P., Cui, W., Dickinson, H. J., Dumm, J., Eisch, J. D., Errando, M., 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., Hütten, M., 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., Maier, G., McArthur, S., McCann, A., Meagher, K., Moriarty, P., Mukherjee, R., Nieto, D., O'Brien, S., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Park, N., Pelassa, V., Petrashyk, A., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Ratliff, G., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Rulten, C., Santander, M., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Vincent, S., Wakely, S. P., Weiner, O. M., Weinstein, A., Wilhelm, A., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present results from multiwavelength observations of the BL Lacertae object 1ES 1741+196, including results in the very-high-energy $\gamma$-ray regime using the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The VERITAS time-averaged spectrum, measured above 180 GeV, is well-modelled by a power law with a spectral index of $2.7\pm0.7_{\mathrm{stat}}\pm0.2_{\mathrm{syst}}$. The integral flux above 180 GeV is $(3.9\pm0.8_{\mathrm{stat}}\pm1.0_{\mathrm{syst}})\times 10^{-8}$ m$^{-2}$ s$^{-1}$, corresponding to 1.6% of the Crab Nebula flux on average. The multiwavelength spectral energy distribution of the source suggests that 1ES 1741+196 is an extreme-high-frequency-peaked BL Lacertae object. The observations analysed in this paper extend over a period of six years, during which time no strong flares were observed in any band. This analysis is therefore one of the few characterizations of a blazar in a non-flaring state., Comment: 8 pages, 5 figures. Accepted for publication in MNRAS
Published: 2016
Full Text: View/download PDF

28. Upper limits from five years of blazar observations with the VERITAS Cherenkov telescopes

Author: Archambault, S., Archer, A., Benbow, W., Bird, R., Biteau, J., Buchovecky, M., Buckley, J. H., Bugaev, V., Byrum, K., Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Eisch, J. D., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Gillanders, G. H., Griffin, S., Grube, J., Gyuk, G., Hütten, M., Hakansson, N., 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., Maier, G., McArthur, S., McCann, A., Meagher, K., Moriarty, P., Mukherjee, R., Nguyen, T., Nieto, D., De Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Park, N., Perkins, J. S., Pichel, A., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Santander, M., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Vincent, S., Wakely, S. P., Weiner, O. M., Weinstein, A., Williams, D. A., Zitzer, B., Fumagalli, M., and Prochaska, J. X.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Between the beginning of its full-scale scientific operations in 2007 and 2012, the VERITAS Cherenkov telescope array observed more than 130 blazars; of these, 26 were detected as very-high-energy (VHE; E>100 GeV) {\gamma}-ray sources. In this work, we present the analysis results of a sample of 114 undetected objects. The observations constitute a total live-time of ~570 hours. The sample includes several unidentified Fermi-Large Area Telescope (LAT) sources (located at high Galactic latitude) as well as all the sources from the second Fermi-LAT catalog which are contained within the field of view of the VERITAS observations. We have also performed optical spectroscopy measurements in order to estimate the redshift of some of these blazars that do not have a spectroscopic distance estimate. We present new optical spectra from the Kast instrument on the Shane telescope at the Lick observatory for 18 blazars included in this work, which allowed for the successful measurement or constraint on the redshift of four of them. For each of the blazars included in our sample we provide the flux upper limit in the VERITAS energy band. We also study the properties of the significance distributions and we present the result of a stacked analysis of the data-set, which shows a 4 {\sigma} excess., Comment: 22 pages; accepted for publication in The Astronomical Journal
Published: 2016
Full Text: View/download PDF

29. TeV Gamma-ray Observations of The Galactic Center Ridge By VERITAS

Author: Archer, A., Benbow, W., Bird, R., Buchovecky, M., Buckley, J. H., Bugaev, V., Byrum, K., Cardenzana, J. V, Cerruti, M., Chen, X., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Eisch, J. D., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Flinders, A., Fortson, L., Furniss, A., Gillanders, G. H., Griffin, S., Grube, J., Gyuk, G., Hakansson, N., Hanna, D., Holder, J., Humensky, T. B., Hutten, M., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., McArthur, S., McCann, A., Meagher, K., Millis, J., Moriarty, P., Mukherjee, R., Nieto, D., Ong, R. A., Park, N., Pelassa, V., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Ratliff, G., Reynolds, P. T., Richards, G. T., Roache, E., Rousselle, J., Santander, M., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Vassiliev, V. V., Wakely, S. P., Weiner, O. M., Weinstein, A., Wilhelm, A., Williams, D. A., Zitzer, B., and Yusef-Zadeh, F.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Galactic Center Ridge has been observed extensively in the past by both GeV and TeV gamma-ray instruments revealing a wealth of structure, including a diffuse component as well as the point sources G0.9+0.1 (a composite supernova remnant) and Sgr A* (believed to be associated with the supermassive black hole located at the center of our Galaxy). Previous very high energy (VHE) gamma-ray observations with the H.E.S.S. experiment have also detected an extended TeV gamma-ray component along the Galactic plane in the >300 GeV gamma-ray regime. Here we report on observations of the Galactic Center Ridge from 2010-2014 by the VERITAS telescope array in the >2 TeV energy range. From these observations we 1.) provide improved measurements of the differential energy spectrum for Sgr A* in the >2 TeV gamma-ray regime, 2.) provide a detection in the >2 TeV gamma-ray emission from the composite SNR G0.9+0.1 and an improved determination of its multi-TeV gamma-ray energy spectrum, 3.) report on the detection of VER J1746-289, a localized enhancement of >2 TeV gamma-ray emission along the Galactic plane., Comment: 9 pages, 5 figures, Accepted for Publication in The Astrophysical Journal
Published: 2016
Full Text: View/download PDF

30. A Search for Brief Optical Flashes Associated with the SETI Target KIC 8462852

Author: Abeysekara, A. U., Archambault, S., Archer, A., Benbow, W., Bird, R., Buchovecky, M., Buckley, J. H., Byrum, K., Cardenzana, J. V, Cerruti, M., Chen, X., 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, N., 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., O'Brien, S., de Bhroithe, A. O'Faolain, Ong, R. A., Otte, A. N., Park, N., Perkins, J. S., Petrashyk, A., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Ratliff, G., Reynolds, P. T., Richards, G. T., Roache, E., Santander, M., Sembroski, G. H., Shahinyan, K., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Vincent, S., Wakely, S. P., Weiner, O. M., Weinstein, A., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: The F-type star KIC 8462852 has recently been identified as an exceptional target for SETI (search for extraterrestrial intelligence) observations. We describe an analysis methodology for optical SETI, which we have used to analyse 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 per 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., Comment: Accepted for publication in ApJ Letters. Fixed a minor error in the title
Published: 2016
Full Text: View/download PDF

31. Exceptionally bright TeV flares from the binary LS I +61$^\circ$ 303

Author: VERITAS Collaboration, Archambault, S., Archer, A., Aune, T., Barnacka, A., Benbow, W., Bird, R., Buchovecky, M., Buckley, J. H., Bugaev, V., Byrum, K., Cardenzana, J. V., Cerruti, M., Chen, X., 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, N., 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., O'Brien, S., de Bhroithe, A. O'Faolain, Ong, R. A., Otte, A. N., Pandel, D., Park, N., Pelassa, V., Pohl, M., Popkow, A., Pueschel, E., 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, I., Tucci, J. V., Tyler, J., Vincent, S., Wakely, S. P., Weiner, O. M., Weinstein, A., Wilhelm, A., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The TeV binary system LS I +61$^\circ$ 303 is known for its regular, non-thermal emission pattern which 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$^\circ$ 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$^\circ$ 303 during the flares, provides constraints on the properties of the accelerator in the source., Comment: 9 pages, 2 figures. Accepted for publication by ApJL
Published: 2016
Full Text: View/download PDF

32. Gamma rays from the quasar PKS 1441+25: story of an escape

Author: Abeysekara, A. U., Archambault, S., Archer, A., Aune, T., Barnacka, A., Benbow, W., Bird, R., Biteau, J., Buckley, J. H., Bugaev, V., Cardenzana, J. V, Cerruti, M., Chen, X., Christiansen, J. L., Ciupik, L., Connolly, M. P., Coppi, P., Cui, W., Dickinson, H. J., Dumm, J., Eisch, J. D., Errando, M., 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., Hütten, M., Håkansson, N., Hanna, D., Holder, J., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Khassen, Y., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Maier, G., McArthur, S., McCann, A., Meagher, K., Moriarty, P., Mukherjee, R., Nieto, D., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Park, N., Perkins, J. S., Petrashyk, A., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Ratliff, G., Reynolds, P. T., Richards, G. T., Roache, E., Rousselle, J., Santander, M., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Todd, N. W., Tucci, J. V., Tyler, J., Vassiliev, V. V., Vincent, S., Wakely, S. P., Weiner, O. M., Weinstein, A., Wilhelm, A., Williams, D. A., Zitzer, B., Smith, P. S., Holoien, T. W. -S., Prieto, J. L., Kochanek, C. S., Stanek, K. Z., Shappee, B., Hovatta, T., Max-Moerbeck, W., Pearson, T. J., Reeves, R. A., Richards, J. L., Readhead, A. C. S., Madejski, G. M., Djorgovski, S. G., Drake, A. J., Graham, M. J., and Mahabal, A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints on the diffuse radiation fields that fill the Universe. The detection of significant emission above 100 GeV from a distant quasar would show that some of the radiated gamma rays escape pair-production interactions with low-energy photons, be it the extragalactic background light (EBL), or the radiation near the supermassive black hole lying at the jet's base. VERITAS detected gamma-ray emission up to 200 GeV from PKS 1441+25 (z=0.939) during April 2015, a period of high activity across all wavelengths. This observation of PKS 1441+25 suggests that the emission region is located thousands of Schwarzschild radii away from the black hole. The gamma-ray detection also sets a stringent upper limit on the near-ultraviolet to near-infrared EBL intensity, suggesting that galaxy surveys have resolved most, if not all, of the sources of the EBL at these wavelengths., Comment: 7 pages, 3 figures, published in ApJ Letters 815, L22 (2015)
Published: 2015
Full Text: View/download PDF

33. Multiwavelength Study of Quiescent States of Mrk 421 with Unprecedented Hard X-Ray Coverage Provided by NuSTAR in 2013

Author: Baloković, M., Paneque, D., Madejski, G., Furniss, A., Chiang, J., team, the NuSTAR, Ajello, M., Alexander, D. M., Barret, D., Blandford, R., Boggs, S. E., Christensen, F. E., Craig, W. W., Forster, K., Giommi, P., Grefenstette, B. W., Hailey, C. J., Harrison, F. A., Hornstrup, A., Kitaguchi, T., Koglin, J. E., Madsen, K. K., Mao, P. H., Miyasaka, H., Mori, K., Perri, M., Pivovaroff, M. J., Puccetti, S., Rana, V., Stern, D., Tagliaferri, G., Urry, C. M., Westergaard, N. J., Zhang, W. W., Zoglauer, A., collaboration, the VERITAS, Archambault, S., Archer, A. A., Barnacka, A., Benbow, W., Bird, R., Buckley, J., Bugaev, V., Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Dickinson, H. J., Dumm, J., Eisch, J. D., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Fortson, L., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Huetten, M., Haakansson, N., Holder, J., Humensky, T. B., Johnson, C. A., Kaaret, P., Kertzman, M., Khassen, Y., Kieda, D., Krause, M., Krennrich, F., Lang, M. J., Maier, G., McArthur, S., Meagher, K., Moriarty, P., Nelson, T., Nieto, D., Ong, R. A., Park, N., Pohl, M., Popkow, A., Pueschel, E., Reynolds, P. T., Richards, G. T., Roache, E., Santander, M., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Todd, N. W., Tucci, J. V., Tyler, J., Vincent, S., Weinstein, A., Wilhelm, A., Williams, D. A., Zitzer, B., collaboration, the MAGIC, Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Banerjee, B., Bangale, P., de Almeida, U. Barres, Barrio, J., González, J. Becerra, Bednarek, W., Bernardini, E., Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carmona, E., Carosi, A., Chatterjee, A., Clavero, R., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., de Angelis, A., De Lotto, B., Wilhelmi, E. D. de Oña, Mendez, C. Delgado, Di Pierro, F., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Elsaesser, D., Fernández-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., Galindo, D., López, R. J. García, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Giammaria, P., Eisenacher, D., Godinović, N., Muñoz, A. González, Guberman, D., Hahn, A., Hanabata, Y., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Hughes, G., Idec, W., Kodani, K., Konno, Y., Kubo, H., Kushida, J., La Barbera, A., Lelas, D., Lindfors, E., Lombardi, S., Longo, F., López, M., López-Coto, R., López-Oramas, A., Lorenz, E., Majumdar, P., Makariev, M., Mallot, K., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Miranda, J. M., Mirzoyan, R., Moralejo, A., Moretti, E., Nakajima, D., Neustroev, V., Niedzwiecki, A., Nievas-Rosillo, M., Nilsson, K., Nishijima, K., Noda, K., Orito, R., Overkemping, A., Paiano, S., Palacio, S., Palatiello, M., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Persic, M., Poutanen, J., Moroni, P. G. Prada, Prandini, E., Puljak, I., Rhode, W., Ribó, M., Rico, J., Garcia, J. Rodriguez, Saito, T., Satalecka, K., Scapin, V., Schultz, C., Schweizer, T., Shore, S. N., Sillanpää, A., Sitarek, J., Snidaric, I., Sobczynska, D., Stamerra, A., Steinbring, T., Strzys, M., Takalo, L. O., Takami, H., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thaele, J., Torres, D. F., Toyama, T., Treves, A., Verguilov, V., Vovk, I., Ward, J. E., Will, M., Wu, M. H., Zanin, R., collaborators, external, Perkins, J., Verrecchia, F., Leto, C., Böttcher, M., Villata, M., Raiteri, C. M., Acosta-Pulido, J. A., Bachev, R., Berdyugin, A., Blinov, D. A., Carnerero, M. I., Chen, W. P., Chinchilla, P., Damljanovic, G., Eswaraiah, C., Grishina, T. S., Ibryamov, S., Jordan, B., Jorstad, S. G., Joshi, M., Kopatskaya, E. N., Kurtanidze, O. M., Kurtanidze, S. O., Larionova, E. G., Larionova, L. V., Larionov, V. M., Latev, G., Lin, H. C., Marscher, A. P., Mokrushina, A. A., Morozova, D. A., Nikolashvili, M. G., Semkov, E., Strigachev, A., Troitskaya, Yu. V., Troitsky, I. S., Vince, O., Barnes, J., Güver, T., Moody, J. W., Sadun, A. C., Sun, S., Hovatta, T., Richards, J. L., Max-Moerbeck, W., Readhead, A. C., Lähteenmäki, A., Tornikoski, M., Tammi, J., Ramakrishnan, V., Reinthal, R., Angelakis, E., Fuhrmann, L., Myserlis, I., Karamanavis, V., Sievers, A., Ungerechts, H., and Zensus, J. A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations and instruments, providing data from radio to very-high-energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity in the 3-79 keV range, revealing that the spectrum softens when the source is dimmer until the X-ray spectral shape saturates into a steep power law with a photon index of approximately 3, with no evidence for an exponential cutoff or additional hard components up to about 80 keV. For the first time, we observed both the synchrotron and the inverse-Compton peaks of the spectral energy distribution (SED) simultaneously shifted to frequencies below the typical quiescent state by an order of magnitude. The fractional variability as a function of photon energy shows a double-bump structure which relates to the two bumps of the broadband SED. In each bump, the variability increases with energy which, in the framework of the synchrotron self-Compton model, implies that the electrons with higher energies are more variable. The measured multi-band variability, the significant X-ray-to-VHE correlation down to some of the lowest fluxes ever observed in both bands, the lack of correlation between optical/UV and X-ray flux, the low degree of polarization and its significant (random) variations, the short estimated electron cooling time, and the significantly longer variability timescale observed in the NuSTAR light curves point toward in-situ electron acceleration, and suggest that there are multiple compact regions contributing to the broadband emission of Mrk 421 during low-activity states., Comment: 32 pages, 14 figures; accepted for publication in ApJ
Published: 2015
Full Text: View/download PDF

34. VERITAS Collaboration Contributions to the 34th International Cosmic Ray Conference

Author: The VERITAS Collaboration, Abeysekara, A. U., Archambault, S., Archer, A., Barnacka, A., Benbow, W., Bird, R., Biteau, J., Buchovecky, M., Buckley, J. H., Bugaev, V., Byrum, K., Cardenzana, J. V, Cerruti, M., Chen, X., Christiansen, J. L., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Coppi, P., Cui, W., Dwarkadas, V. V., Eisch, J. D., Errando, M., Falcone, A., Feng, Q., Alonso, M. Fernandez, Finley, J. P., Fleischhack, H., Flinders, A., Fortin, P., Fortson, L., Furniss, A., Gillanders, G. H., Griffin, S., Griffiths, S. T., Gyuk, G., Hütten, M., Hanna, D., Holder, J., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kertzman, M., Khassen, Y., 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., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Pandel, D., Park, N., Pelassa, V., Perkins, J. S., Petrashyk, A., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Santander, M., Schlenstedt, S., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Vassiliev, V. V., Vincent, S., Wakely, S. P., Weiner, O. M., Weinstein, A., Wilhelm, A., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Compilation of papers presented by the VERITAS Collaboration at the 34th International Cosmic Ray Conference (ICRC), held July 30 through August 6, 2015 in The Hague, The Netherlands., Comment: 1 html page. 2015 ICRC, The Hague, The Netherlands. A full list of author affiliations can be found at this link: http://veritas.sao.arizona.edu/conferences/authors?icrc2015
Published: 2015

35. Science Highlights from VERITAS

Author: Staszak, D., Abeysekara, A. U., Archambault, S., Archer, A., Barnacka, A., Benbow, W., Bird, R., Biteau, J., Buchovecky, M., Buckley, J. H., Bugaev, V., Byrum, K., Cardenzana, J. V, Cerruti, M., Chen, X., Christiansen, J. L., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Coppi, P., Cui, W., Dwarkadas, V. V., Eisch, J. D., Errando, M., Falcone, A., Feng, Q., Alonso, M. Fernandez, Finley, J. P., Fleischhack, H., Flinders, A., Fortin, P., Fortson, L., Furniss, A., Gillanders, G. H., Griffin, S., Griffiths, S. T., Gyuk, G., Hütten, M., Hanna, D., Holder, J., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kertzman, M., Khassen, Y., 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., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Pandel, D., Park, N., Pelassa, V., Perkins, J. S., Pohl, M., Popkow, A., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Santander, M., Schlenstedt, S., Sembroski, G. H., Shahinyan, K., Smith, A. W., Telezhinsky, I., Tucci, J. V., Tyler, J., Vassiliev, V. V., Vincent, S., Wakely, S. P., Weiner, O. M., Weinstein, A., Wilhelm, A., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is a ground-based array located at the Fred Lawrence Whipple Observatory in southern Arizona and is one of the world's most sensitive gamma-ray instruments at energies of 85 GeV to $>$30 TeV. VERITAS has a wide scientific reach that includes the study of extragalactic and Galactic objects as well as the search for astrophysical signatures of dark matter and the measurement of cosmic rays. In this paper, we will summarize the current status of the VERITAS observatory and present some of the scientific highlights from the last two years, focusing in particular on those results shown at the 2015 ICRC in The Hague, Netherlands., Comment: To appear in the Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands
Published: 2015

36. First NuSTAR Observations of Mrk 501 within a Radio to TeV Multi-Instrument Campaign

Author: Furniss, A., Noda, K., Boggs, S., Chiang, J., Christensen, F., Craig, W., Giommi, P ., Hailey, C., Harisson, F., Madejski, G., Nalewajko, K., Perri, M., Stern, D., Urry, M., Verrecchia, F., Zhang, W., Ahnen, M. L., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Banerjee, B., Bangale, P., de Almeida, U. Barres, Barrio, J. A., Gonzalez, J. Becerra, Bednarek, W., Bernardini, E., Biasuzzi, B., Biland, A., Blanch, O., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carmona, E., Carosi, A., Chatterjee, A., Clavero, R., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., De Angelis, A., De Caneva, G., De Lotto, B., Wilhelmi, E. de Ona, Mendez, C. Delgado, Di Pierro, F., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Glawion, D. Eisenacher, Elsaesser, D., Fernandez-Barral, A., Fidalgo, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., Galindo, D., Lopez, R. J. Garcia, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Giammaria, P., Godinovic, N., Munoz, A. Gonzalez, Guberman, D., Hanabata, Y., Hayashida, M., Herrera, J., Hose, J., Hrupec, D., Hughes, G., Idec, W., Kellermann, H., Kodani, K., Konno, Y., Kubo, H., Kushida, J., La Barbera, A., Lelas, D., Lewandowska, N., Lindfors, E., Lombardi, S., Longo, F., Lopez, M., Lopez-Coto, R., Lopez-Oramas, A., Lorenz, E., Majumdar, P., Makariev, M., Mallot, K., Maneva, G., Manganaro, M., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martinez, M., Mazin, D., Menzel, U., Miranda, J. M., Mirzoyan, R., Moralejo, A., Nakajima, D., Neustroev, V., Niedzwiecki, A., Rosillo, M. Nievas, Nilsson, K., Nishijima, K., Orito, R., Overkemping, A., Paiano, S., Palacio, J., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Persic, M., Poutanen, J., Moroni, P. G. Prada, Prandini, E., Puljak, I., Reinthal, R., Rhode, W., Ribo, M., Rico, J., Garcia, J. Rodriguez, Saito, T., Saito, K., Satalecka, K., Scapin, V., Schultz, C., Schweizer, T., Shore, S. N., Sillanpaa, A., Sitarek, J., Snidaric, I., Sobczynska, D., Stamerra, A., Steinbring, T., Strzys, M., Takalo, L., Takami, H., Tavecchio, F., Temnikov, P., Terzic, T., Tescaro, D., Teshima, M., Thaele, J., Torres, D. F., Toyama, T., Treves, A., Verguilov, V., Vovk, I., Will, M., Zanin, R., Archer, A., Benbow, W., Bird, R., Biteau, J., Bugaev, V., Cardenzana, J. V, Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Dickinson, H. J., Dumm, J., Eisch, J. D., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Gerard, L., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Haakansson, N., Holder, J., Humensky, T. B., Johnson, C. A., Kaaret, P., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Lang, M. J., Lin, T. T. Y., Maier, G., McArthur, S., McCann, A., Meagher, K., Moriarty, P., Mukherjee, R., Nieto, D., de Bhroithe, A. O'Faolain, Ong, R. A., Park, N., Petry, D., Pohl, M., Popkow, A., Ragan, K., Ratliff, G., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Santander, M., Sembroski, G. H., Shahinyan, K., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Vassiliev, V. V., Wakely, S. P., Weiner, O. M., Weinstein, A., Wilhelm, A., Williams, D. A., Zitzer, B., Fuhrmann, O. Vince L., Angelakis, E., Karamanavis, V., Myserlis, I., Krichbaum, T. P., Zensus, J. A., Ungerechts, H., Sievers, A., Bachev, R., Bottcher, M., Chen, W. P., Damljanovic, G., Eswaraiah, C., Guver, T., Hovatta, T., Hughes, Z., Ibryamov, S. . I., Joner, M. D., Jordan, B., Jorstad, S. G., Joshi, M., Kataoka, J., Kurtanidze, O. M., Kurtanidze, S. O., Lahteenmaki, A., Latev, G., Lin, H. C., Larionov, V. M., Mokrushina, A. A., Morozova, D. A., Nikolashvili, M. G., Raiteri, C. M., Ramakrishnan, V., Readhead, A. C. R., Sadun, A. C., Sigua, L. A., Semkov, E. H., Strigachev, A., Tammi, J., Tornikoski, M., Troitsky, Y. V. Troitskaya I. S., and Villata, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on simultaneous broadband observations of the TeV-emitting blazar Markarian 501 between 1 April and 10 August 2013, including the first detailed characterization of the synchrotron peak with Swift and NuSTAR. During the campaign, the nearby BL Lac object was observed in both a quiescent and an elevated state. The broadband campaign includes observations with NuSTAR, MAGIC, VERITAS, the Fermi Large Area Telescope (LAT), Swift X-ray Telescope and UV Optical Telescope, various ground-based optical instruments, including the GASP-WEBT program, as well as radio observations by OVRO, Mets\"ahovi and the F-Gamma consortium. Some of the MAGIC observations were affected by a sand layer from the Saharan desert, and had to be corrected using event-by-event corrections derived with a LIDAR (LIght Detection And Ranging) facility. This is the first time that LIDAR information is used to produce a physics result with Cherenkov Telescope data taken during adverse atmospheric conditions, and hence sets a precedent for the current and future ground-based gamma-ray instruments. The NuSTAR instrument provides unprecedented sensitivity in hard X-rays, showing the source to display a spectral energy distribution between 3 and 79 keV consistent with a log-parabolic spectrum and hard X-ray variability on hour timescales. None (of the four extended NuSTAR observations) shows evidence of the onset of inverse-Compton emission at hard X-ray energies. We apply a single-zone equilibrium synchrotron self-Compton model to five simultaneous broadband spectral energy distributions. We find that the synchrotron self-Compton model can reproduce the observed broadband states through a decrease in the magnetic field strength coinciding with an increase in the luminosity and hardness of the relativistic leptons responsible for the high-energy emission., Comment: Accepted for publication in ApJ
Published: 2015
Full Text: View/download PDF

37. VERITAS detection of $\gamma$-ray flaring activity from the BL Lac object 1ES 1727+502 during bright moonlight observations

Author: Archambault, S., Archer, A., Beilicke, M., Benbow, W., Bird, R., Biteau, J., Bouvier, A., Bugaev, V., Cardenzana, J. V, Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Dickinson, H. J., Dumm, J., Eisch, J. D., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Håkansson, N., Hanna, D., Holder, J., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., 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., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Park, N., Pohl, M., Popkow, A., Prokoph, H., Pueschel, E., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Santander, M., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Varlotta, A., Vincent, S., Wakely, S. P., Weinstein, A., Welsing, R., Wilhelm, A., Williams, D. A., Zitzer, B., and Hughes, Z. D.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: During moonlit nights, observations with ground-based Cherenkov telescopes at very high energies (VHE, $E>100$ GeV) are constrained since the photomultiplier tubes (PMTs) in the telescope camera are extremely sensitive to the background moonlight. Observations with the VERITAS telescopes in the standard configuration are performed only with a moon illumination less than 35$\%$ of full moon. Since 2012, the VERITAS collaboration has implemented a new observing mode under bright moonlight, by either reducing the voltage applied to the PMTs (reduced-high-voltage configuration, RHV), or by utilizing UV-transparent filters. While these operating modes result in lower sensitivity and increased energy thresholds, the extension of the available observing time is useful for monitoring variable sources such as blazars and sources requiring spectral measurements at the highest energies. In this paper we report the detection of $\gamma$-ray flaring activity from the BL Lac object 1ES 1727+502 during RHV observations. This detection represents the first evidence of VHE variability from this blazar. The integral flux is $(1.1\pm0.2)\times10^{-11}\mathrm{cm^{-2}s^{-1}}$ above 250 GeV, which is about five times higher than the low-flux state. The detection triggered additional \veritas\ observations during standard dark-time. Multiwavelength observations with the FLWO 48" telescope, and the Swift and Fermi satellites are presented and used to produce the first spectral energy distribution (SED) of this object during $\gamma$-ray flaring activity. The SED is then fitted with a standard synchrotron-self-Compton model, placing constraints on the properties of the emitting region and of the acceleration mechanism at the origin of the relativistic particle population in the jet., Comment: 11 pages, 3 figures, accepted for publication in ApJ
Published: 2015
Full Text: View/download PDF

38. The VERITAS Dark Matter Program

Author: Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: In the cosmological paradigm, cold dark matter (DM) dominates the mass content of the Universe and is present at every scale. Candidates for DM include many extensions of the standard model, with a weakly interacting massive particle (WIMP) in the mass range from $\sim$10 GeV to greater than 10 TeV. The self-annihilation or decay of WIMPs in astrophysical regions of high DM density can produce secondary particles including very high energy (VHE) gamma rays with energy up to the DM particle mass. VERITAS, an array of atmospheric Cherenkov telescopes, sensitive to VHE gamma rays in the 85 GeV - 30 TeV energy range, has been utilized for DM searches. The possible astrophysical objects considered to be candidates for indirect DM detection are VERITAS dwarf spheroidal galaxies (dSphs) of the Local Group and the Galactic Center, among others. This presentation reports on our extensive observations of these targets and constraints of the dark matter physics from these objects, including the methodology and preliminary results of a combined DM search of five dSphs., Comment: 2014 Fermi Symposium proceedings - eConf C14102.1
Published: 2015

39. The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies

Author: MAGIC Collaboration, Aleksić, J., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Bangale, P., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Berger, K., Bernardini, E., Biland, A., Blanch, O., Bock, R. K., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carmona, E., Carosi, A., Fidalgo, D. Carreto, Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., De Angelis, A., De Caneva, G., De Lotto, B., Mendez, C. Delgado, Doert, M., Domínguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Eisenacher, D., Elsaesser, D., Farina, E., Ferenc, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., López, R. J. García, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Giavitto, G., Godinović, N., noz, A. González Mu\, Gozzini, S. R., Hadamek, A., Hadasch, D., Herrero, A., Hildebrand, D., Hose, J., Hrupec, D., Idec, W., Kadenius, V., Kellermann, H., Knoetig, M. L., Krause, J., Kushida, J., La Barbera, A., Lelas, D., Lewandowska, N., Lindfors, E., Longo, F., Lombardi, S., López, M., López-Coto, R., López-Oramas, A., Lorenz, E., Lozano, I., Makariev, M., Mallot, K., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Meucci, M., Miranda, J. M., Mirzoyan, R., Moralejo, A., Munar-Adrover, P., Nakajima, D., Niedzwiecki, A., Nilsson, K., Nowak, N., Orito, R., Overkemping, A., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Partini, S., Persic, M., Prada, F., Moroni, P. G. Prada, Prandini, E., Preziuso, S., Puljak, I., Reinthal, R., Rhode, W., Ribó, M., Rico, J., Garcia, J. Rodriguez, Rügamer, S., Saggion, A., Saito, K., Salvati, M., Satalecka, K., Scalzotto, V., Scapin, V., Schultz, C., Schweizer, T., Shore, S. N., Sillanpää, A., Sitarek, J., Snidaric, I., Sobczynska, D., Spanier, F., Stamatescu, V., Stamerra, A., Steinbring, T., Storz, J., Sun, S., Surić, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thaele, J., Tibolla, O., Torres, D. F., Toyama, T., Treves, A., Uellenbeck, M., Vogler, P., Wagner, R. M., Zandanel, F., Zanin, R., collaboration, VERITAS, Archambault, S., Behera, B., Beilicke, M., Benbow, W., Bird, R., Buckley, J. H., Bugaev, V., Cerruti, M., Chen, X., Ciupik, L., Collins-Hughes, E., Cui, W., Dumm, J., Eisch, J. D., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Hanna, D., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Kumar, S., Lang, M. J., Maier, G., McArthur, S., Meagher, K., Moriarty, P., Mukherjee, R., Ong, R. A., Otte, A. N., Park, N., Pichel, A., Pohl, M., Popkow, A., Prokoph, H., Quinn, J., Ragan, K., Rajotte, J., Reynolds, P. T., Richards, G. T., Roache, E., Rovero, A. C., Sembroski, G. H., Shahinyan, K., Staszak, D., Telezhinsky, I., Theiling, M., Tucci, J. V., Tyler, J., Varlotta, A., Wakely, S. P., Weekes, T. C., Weinstein, A., Welsing, R., Wilhelm, A., Williams, D. A., Zitzer, B., collaborators, External, Villata, M., Raiteri, C., Aller, H. D., Aller, M. F., Chen, W. P., Jordan, B., Koptelova, E., Kurtanidze, O. M., Lähteenmäki, A., McBreen, B., Larionov, V. M., Lin, C. S., Nikolashvili, M. G., Angelakis, E., Capalbi, M., nana, A. Carrami\, Carrasco, L., Cassaro, P., Cesarini, A., Fuhrmann, L., Giroletti, M., Hovatta, T., Krichbaum, T. P., Krimm, H. A., Max-Moerbeck, W., Moody, J. W., Maccaferri, G., Mori, Y., Nestoras, I., Orlati, A., Pace, C., Pearson, R., Perri, M., Readhead, A. C. S., Richards, J. L., Sadun, A. C., Sakamoto, T., Tammi, J., Tornikoski, M., Yatsu, Y., and Zook, A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We performed a 4.5-month multi-instrument campaign (from radio to VHE gamma rays) on Mrk421 between January 2009 and June 2009, which included VLBA, F-GAMMA, GASP-WEBT, Swift, RXTE, Fermi-LAT, MAGIC, and Whipple, among other instruments and collaborations. Mrk421 was found in its typical (non-flaring) activity state, with a VHE flux of about half that of the Crab Nebula, yet the light curves show significant variability at all wavelengths, the highest variability being in the X-rays. We determined the power spectral densities (PSD) at most wavelengths and found that all PSDs can be described by power-laws without a break, and with indices consistent with pink/red-noise behavior. We observed a harder-when-brighter behavior in the X-ray spectra and measured a positive correlation between VHE and X-ray fluxes with zero time lag. Such characteristics have been reported many times during flaring activity, but here they are reported for the first time in the non-flaring state. We also observed an overall anti-correlation between optical/UV and X-rays extending over the duration of the campaign. The harder-when-brighter behavior in the X-ray spectra and the measured positive X-ray/VHE correlation during the 2009 multi-wavelength campaign suggests that the physical processes dominating the emission during non-flaring states have similarities with those occurring during flaring activity. In particular, this observation supports leptonic scenarios as being responsible for the emission of Mrk421 during non-flaring activity. Such a temporally extended X-ray/VHE correlation is not driven by any single flaring event, and hence is difficult to explain within the standard hadronic scenarios. The highest variability is observed in the X-ray band, which, within the one-zone synchrotron self-Compton scenario, indicates that the electron energy distribution is most variable at the highest energies., Comment: Accepted for publication in A&A, 18 pages, 14 figures (v2 has a small modification in the acknowledgments, and also corrects a typo in the field "author" in the metadata)
Published: 2015
Full Text: View/download PDF

40. A Search for Pulsations from Geminga Above 100 GeV with VERITAS

Author: Aliu, E., Archambault, S., Archer, A., Aune, T., Barnacka, A., Beilicke, M., Benbow, W., Bird, R., Buckley, J. H., Bugaev, V., Byrum, K., Cardenzana, J. V, Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Dickinson, H. J., Dumm, J., Eisch, J. D., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Hakansson, N., Hanna, D., Holder, J., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kertzman, M., Kieda, D., Krennrich, F., Kumar, S., Lang, M. J., Lyutikov, M., Madhavan, A. S, Maier, G., McArthur, S., McCann, A., Meagher, K., Millis, J., Moriarty, P., Mukherjee, R., Nieto, D., de Bhroithe, A. O'Faolain, Ong, R. A., Otte, A. N., Park, N., Pohl, M., Popkow, A., Prokoph, H., Pueschel, E., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Santander, M., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Varlotta, A., Vincent, S., Wakely, S. P., Weinstein, A., Williams, D. A., Zajczyk, A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present the results of 71.6 hours of observations of the Geminga pulsar (PSR J0633+1746) with the VERITAS very-high-energy gamma-ray telescope array. Data taken with VERITAS between November 2007 and February 2013 were phase-folded using a Geminga pulsar timing solution derived from data recorded by the XMM-\emph{Newton} and \emph{Fermi}-LAT space telescopes. No significant pulsed emission above 100 GeV is observed, and we report upper limits at the 95% confidence level on the integral flux above 135 GeV (spectral analysis threshold) of 4.0$\times10^{-13}$ s$^{-1}$ cm$^{-2}$ and 1.7$\times10^{-13}$ s$^{-1}$ cm$^{-2}$ for the two principal peaks in the emission profile. These upper limits, placed in context with phase-resolved spectral energy distributions determined from five years of data from the \emph{Fermi}-LAT, constrain possible hardening of the Geminga pulsar emission spectra above $\sim$50 GeV., Comment: 7 pages, 2 figures, 2 tables. Accepted for publication in ApJ
Published: 2014
Full Text: View/download PDF

41. Investigating Broadband Variability of the TeV Blazar 1ES 1959+650

Author: Aliu, E., Archambault, S., Arlen, T., Aune, T., Barnacka, A., Beilicke, M., Benbow, W., Berger, K., Bird, R., Bouvier, A., Buckley, J. H., Bugaev, V., Cerruti, M., Chen, X., Ciupik, L., Collins-Hughes, E., Connolly, M. P., Cui, W., Dumm, J., Eisch, J. D., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Hakansson, N., Hanna, D., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., Madhavan, A. S, Majumdar, P., McArthur, S., McCann, A., Meagher, K., Millis, J., Moriarty, P., Mukherjee, R., Nelson, T., Nieto, D., de Bhroithe, A. O'Faolain, Ong, R. A., Otte, A. N., Park, N., Perkins, J. S., Pohl, M., Popkow, A., Prokoph, H., Quinn, J., Ragan, K., Rajotte, J., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Sadun, A., Santander, M., Sembroski, G. H., Shahinyan, K., Sheidaei, F., Smith, A. W., Staszak, D., Telezhinsky, I., Theiling, M., Tyler, J., Varlotta, A., Vassiliev, V. V., Vincent, S., Wakely, S. P., Weekes, T. C., Weinstein, A., Welsing, R., Wilhelm, A., Williams, D. A., Zitzer, B., Böttcher, M., and Fumagalli, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band observations by the robotic telescopes Super-LOTIS and iTelescope, UV observations by Swift UVOT, X-ray observations by the Swift X-ray Telescope (XRT), high-energy gamma-ray observations with the Fermi Large Area Telescope (LAT) and very-high-energy (VHE) gamma-ray observations by VERITAS above 315 GeV, all taken between 17 April 2012 and 1 June 2012 (MJD 56034 and 56079). The contemporaneous variability of the broadband spectral energy distribution is explored in the context of a simple synchrotron self Compton (SSC) model. In the SSC emission scenario, we find that the parameters required to represent the high state are significantly different than those in the low state. Motivated by possible evidence of gas in the vicinity of the blazar, we also investigate a reflected-emission model to describe the observed variability pattern. This model assumes that the non-thermal emission from the jet is reflected by a nearby cloud of gas, allowing the reflected emission to re-enter the blob and produce an elevated gamma-ray state with no simultaneous elevated synchrotron flux. The model applied here, although not required to explain the observed variability pattern, represents one possible scenario which can describe the observations. As applied to an elevated VHE state of 66% of the Crab Nebula flux, observed on a single night during the observation period, the reflected-emission scenario does not support a purely leptonic non-thermal emission mechanism. The reflected emission model does, however, predict a reflected photon field with sufficient energy to enable elevated gamma-ray emission via pion production with protons of energies between 10 and 100 TeV., Comment: Accepted by ApJ
Published: 2014
Full Text: View/download PDF

42. VERITAS Observations of the BL Lac Object PG 1553+113

Author: Aliu, E., Archer, A., Aune, T., Barnacka, A., Behera, B., Beilicke, M., Benbow, W., Berger, K., Bird, R., Buckley, J. H., Bugaev, V., Byrum, K., Cardenzana, J. V, Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Dickinson, H. J., Dumm, J., Eisch, J. D., Errando, M., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Håkansson, N., Hanna, D., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kertzman, P. Kar M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Kumar, S., Lang, M. J., Madhavan, A., McArthur, S., McCann, A., Meagher, K., Millis, J., Moriarty, P., Nieto, D., de Bhróithe, A. O'Faoláin, Ong, R. A., Orr, M., Otte, A. N., Park, N., Perkins, J. S., Pohl, M., Popkow, A., Prokoph, H., Pueschel, E., Quinn, J., Ragan, K., Rajotte, J., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Sembroski, G. H., Shahinyan, K., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Varlotta, A., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Welsing, R., Wilhelm, A., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning the years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 and 560\,GeV, is well described by a power law with a spectral index of $4.33 \pm 0.09$. The time-averaged integral flux above $200\,$GeV measured for this period was $(1.69 \pm 0.06) \times 10^{-11} \, \mathrm{ph} \, \mathrm{cm}^{-2} \, \mathrm{s}^{-1}$, corresponding to 6.9\% of the Crab Nebula flux. We also present the combined $\gamma$-ray spectrum from the Fermi Large Area Telescope and VERITAS covering an energy range from 100~MeV to 560~GeV. The data are well fit by a power law with an exponential cutoff at $\rm {101.9 \pm 3.2 \, \mathrm{GeV}} $. The origin of the cutoff could be intrinsic to PG~1553+113 or be due to the $\gamma$-ray opacity of our universe through pair production off the extragalactic background light (EBL). Given lower limits to the redshift of $\rm z \negthinspace > \negthinspace 0.395$ based on optical/UV observations of PG~1553+113, the cutoff would be dominated by EBL absorption. Conversely, the small statistical uncertainties of the VERITAS energy spectrum have allowed us to provide a robust upper limit on the redshift of PG 1553+113 of $z \negthinspace \leq \negthinspace 0.62$. A strongly-elevated mean flux of $(2.50 \pm 0.14) \times 10^{-11} \, \mathrm{ph} \, \mathrm{cm}^{-2} \, \mathrm{s}^{-1}$ (10.3\% of the Crab Nebula flux) was observed during 2012, with the daily flux reaching as high as $(4.44 \pm 0.71) \times 10^{-11} \, \mathrm{ph} \, \mathrm{cm}^{-2} \, \mathrm{s}^{-1}$ (18.3\% of the Crab Nebula flux) on MJD 56048. The light curve measured during the 2012 observing season is marginally inconsistent with a steady flux, giving a $\chi^2$ probability for a steady flux of 0.03\%., Comment: in press in ApJ, 2014
Published: 2014
Full Text: View/download PDF

43. The most powerful flaring activity from the NLSy1 PMN J0948+0022

Author: D'Ammando, F., Orienti, M., Finke, J., Raiteri, C. M., Hovatta, T., Larsson, J., Max-Moerbeck, W., Perkins, J., Readhead, A. C. S., Richards, J. L., Beilicke, M., Benbow, W., Berger, K., Bird, R., Bugaev, V., Cardenzana, J. V., Cerruti, M., Chen, X., Ciupik, L., Dickinson, H. J., Eisch, J. D., Errando, M., Falcone, A., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Gerard, L., Gillanders, G. H., Griffiths, S. T., Grube, J., Gyuk, G., Hakansson, N., Holder, J., Humensky, T. B., Kar, P., Kertzman, M., Khassen, Y., Kieda, D., Krennrich, F., Kumar, S., Lang, M. J., Maier, G., McCann, A., Meagher, K., Moriarty, P., Mukherjee, R., Nieto, D., de Bhroithe, A. O' Faolain, Ong, R. A., Otte, A. N., Pohl, M., Popkow, A., Prokoph, H., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Rousselle, J., Santander, M., Sembroski, G. H., Smith, A. W., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Varlotta, A., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Welsing, R., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in gamma rays, PMN J0948+0022 ($z$ = 0.5846). A gamma-ray flare was observed by the Large Area Telescope on board Fermi during 2012 December-2013 January, reaching a daily peak flux in the 0.1-100 GeV energy range of (155 $\pm$ 31) $\times$10$^{-8}$ ph cm$^{-2}$ s$^{-1}$ on 2013 January 1, corresponding to an apparent isotropic luminosity of about 1.5$\times$10$^{48}$ erg s$^{-1}$. The gamma-ray flaring period triggered Swift and VERITAS observations in addition to radio and optical monitoring by OVRO, MOJAVE, and CRTS. A strong flare was observed in optical, UV, and X-rays on 2012 December 30, quasi-simultaneously to the gamma-ray flare, reaching a record flux for this source from optical to gamma rays. VERITAS observations at very high energy (E > 100 GeV) during 2013 January 6-17 resulted in an upper limit of F (> 0.2 TeV) < 4.0$\times$10$^{-12}$ ph cm$^{-2}$ s$^{-1}$. We compared the spectral energy distribution (SED) of the flaring state in 2013 January with that of an intermediate state observed in 2011. The two SEDs, modelled as synchrotron emission and an external Compton scattering of seed photons from a dust torus, can be modelled by changing both the electron distribution parameters and the magnetic field., Comment: 13 pages, 5 Figures, 5 Tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society
Published: 2014
Full Text: View/download PDF

44. Multiwavelength observations of Mrk 501 in 2008

Author: MAGIC Collaboration, Aleksić, J., Ansoldi, S., Antonelli, L. A., Antoranz, P., Babic, A., Bangale, P., de Almeida, U. Barres, Barrio, J. A., González, J. Becerra, Bednarek, W., Berger, K., Bernardini, E., Biland, A., Blanch, O., Bock, R. K., Bonnefoy, S., Bonnoli, G., Borracci, F., Bretz, T., Carmona, E., Carosi, A., Fidalgo, D. Carreto, Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., Da Vela, P., Dazzi, F., De Angelis, A., De Caneva, G., De Lotto, B., Mendez, C. Delgado, Doert, M., Domínguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Einecke, S., Eisenacher, D., Elsaesser, D., Farina, E., Ferenc, D., Fonseca, M. V., Font, L., Frantzen, K., Fruck, C., López, R. J. García, Garczarczyk, M., Terrats, D. Garrido, Gaug, M., Giavitto, G., Godinović, N., Muñoz, A. González, Gozzini, S. R., Hadamek, A., Hadasch, D., Herrero, A., Hildebrand, D., Hose, J., Hrupec, D., Idec, W., Kadenius, V., Kellermann, H., Knoetig, M. L., Krause, J., Kushida, J., La Barbera, A., Lelas, D., Lewandowska, N., Lindfors, E., Lombardi, S., López, M., López-Coto, R., López-Oramas, A., Lorenz, E., Lozano, I., Makariev, M., Mallot, K., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Marcote, B., Mariotti, M., Martínez, M., Mazin, D., Menzel, U., Meucci, M., Miranda, J. M., Mirzoyan, R., Moralejo, A., Munar-Adrover, P., Nakajima, D., Niedzwiecki, A., Nilsson, K., Nowak, N., Orito, R., Overkemping, A., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Paredes-Fortuny, X., Partini, S., Persic, M., Prada, F., Moroni, P. G. Prada, Prandini, E., Preziuso, S., Puljak, I., Reinthal, R., Rhode, W., Ribó, M., Rico, J., Garcia, J. Rodriguez, Rügamer, S., Saggion, A., Saito, T., Saito, K., Salvati, M., Satalecka, K., Scalzotto, V., Scapin, V., Schultz, C., Schweizer, T., Shore, S. N., Sillanpää, A., Sitarek, J., Snidaric, I., Sobczynska, D., Spanier, F., Stamatescu, V., Stamerra, A., Steinbring, T., Storz, J., Sun, S., Surić, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thaele, J., Tibolla, O., Torres, D. F., Toyama, T., Treves, A., Uellenbeck, M., Vogler, P., Wagner, R. M., Zandanel, F., Zanin, R., Collaboration, VERITAS, Behera, B., Beilicke, M., Benbow, W., Bird, R., Bouvier, A., Bugaev, V., Cerruti, M., Chen, X., Ciupik, L., Collins-Hughes, E., Cui, W., Duke, C., Dumm, J., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Galante, N., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Hanna, D., Holder, J., Johnson, C. A., Kaaret, P., Kertzman, M., Kieda, D., Krawczynski, H., Lang, M. J., Madhavan, A. S, Maier, G., Majumdar, P., Meagher, K., Moriarty, P., Mukherjee, R., Nieto, D., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Pichel, A., Pohl, M., Popkow, A., Prokoph, H., Quinn, J., Rajotte, J., Ratliff, G., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Sembroski, G. H., Shahinyan, K., Sheidaei, F., Smith, A. W., Staszak, D., Telezhinsky, I., Theiling, M., Tyler, J., Varlotta, A., Vincent, S., Wakely, S. P., Weekes, T. C., Welsing, R., Williams, D. A., Zajczyk, A., Zitzer, B., Collaborators, External, Villata, M., Raiteri, C. M., Ajello, M., Perri, M., Aller, H. D., Aller, M. F., Larionov, V. M., Efimova, N. V., Konstantinova, T. S., Kopatskaya, E. N., Chen, W. P., Koptelova, E., Hsiao, H. Y., Kurtanidze, O. M., Nikolashvili, M. G., Kimeridze, G. N., Jordan, B., Leto, P., Buemi, C. S., Trigilio, C., Umana, G., Lahtenmaki, A., Nieppola, E., Tornikoski, M., Sainio, J., Giroletti, M., Cesarini, A., Fuhrmann, L., Kovalev, Yu. A., and Kovalev, Y. Y.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Mrk 501 is one of the brightest blazars at TeV energies and has been extensively studied since its first VHE detection in 1996. Our goal is to characterize in detail the source gamma-ray emission, together with the radio-to-X-ray emission, during the non-flaring (low) activity, which is less often studied than the occasional flaring (high) activity. We organized a multiwavelength (MW) campaign on Mrk 501 between March and May 2008. This multi-instrument effort included the most sensitive VHE gamma-ray instruments in the northern hemisphere, namely the imaging atmospheric Cherenkov telescopes MAGIC and VERITAS, as well as Swift, RXTE, the F-GAMMA, GASP-WEBT, and other collaborations and instruments. Mrk 501 was found to be in a low state of activity during the campaign, with a VHE flux in the range of 10%-20% of the Crab nebula flux. Nevertheless, significant flux variations were detected with various instruments, with a trend of increasing variability with energy. The broadband spectral energy distribution during the two different emission states of the campaign can be adequately described within the homogeneous one-zone synchrotron self-Compton model, with the (slightly) higher state described by an increase in the electron number density. This agrees with previous studies of the broadband emission of this source during flaring and non-flaring states. We report for the first time a tentative X-ray-to-VHE correlation during a low VHE activity. Although marginally significant, this positive correlation between X-ray and VHE, which has been reported many times during flaring activity, suggests that the mechanisms that dominate the X-ray/VHE emission during non-flaring-activity are not substantially different from those that are responsible for the emission during flaring activity., Comment: Accepted for publication in A&A
Published: 2014
Full Text: View/download PDF

45. Constraints on Very High Energy Emission from GRB 130427A

Author: Aliu, E., Aune, T., Barnacka, A., Beilicke, M., Benbow, W., Berger, K., Biteau, J., Buckley, J. H., Bugaev, V., Byrum, K., Cardenzana, J. V, Cerruti, M., Chen, X., Ciupik, L., Connaughton, V., Cui, W., Dickinson, H. J., Eisch, J. D., Errando, M., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Håkansson, N., Hanna, D., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., Madhavan, A. S., Maier, G., McArthur, S., McCann, A., Meagher, K., Millis, J., Moriarty, P., Mukherjee, R., Nieto, D., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Park, N., Pohl, M., Popkow, A., Prokoph, H., Pueschel, E., Quinn, J., Ragan, K., Rajotte, J., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Sembroski, G. H., Shahinyan, K., Smith, A. W., Staszak, D., Telezhinsky, I., Tucci, J. V., Tyler, J., Varlotta, A., Vassiliev, V. V., Vincent, S., Wakely, S. P., Weiner, O. M., Weinstein, A., Welsing, R., Wilhelm, A., Williams, D. A., Zitzer, B., McEnery, J. E., Perkins, J. S., Veres, P., and Zhu, S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: Prompt emission from the very fluent and nearby (z=0.34) gamma-ray burst GRB 130427A was detected by several orbiting telescopes and by ground-based, wide-field-of-view optical transient monitors. Apart from the intensity and proximity of this GRB, it is exceptional due to the extremely long-lived high-energy (100 MeV to 100 GeV) gamma-ray emission, which was detected by the Large Area Telescope on the Fermi Gamma-ray Space Telescope for ~70 ks after the initial burst. The persistent, hard-spectrum, high-energy emission suggests that the highest-energy gamma rays may have been produced via synchrotron self-Compton processes though there is also evidence that the high-energy emission may instead be an extension of the synchrotron spectrum. VERITAS, a ground-based imaging atmospheric Cherenkov telescope array, began follow-up observations of GRB 130427A ~71 ks (~20 hr) after the onset of the burst. The GRB was not detected with VERITAS; however, the high elevation of the observations, coupled with the low redshift of the GRB, make VERITAS a very sensitive probe of the emission from GRB 130427A for E > 100 GeV. The non-detection and consequent upper limit derived place constraints on the synchrotron self-Compton model of high-energy gamma-ray emission from this burst., Comment: 22 pages, 4 figures, 1 table
Published: 2014
Full Text: View/download PDF

46. Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 8: Instrumentation Frontier

Author: Demarteau, M., Lipton, R., Nicholson, H., Shipsey, I., Akerib, D., Albayrak-Yetkin, A., Alexander, J., Anderson, J., Artuso, M., Asner, D., Ball, R., Battaglia, M., Bebek, C., Beene, J., Benhammou, Y., Bentefour, E., Bergevin, M., Bernstein, A., Bilki, B., Blucher, E., Bolla, G., Bortoletto, D., Bowden, N., Brooijmans, G., Byrum, K., Cabrera, B., Cancelo, G., Carlstrom, J., Casey, B., Chang, C., Chapman, J., Chen, C. H., Childres, I., Christian, D., Convery, M., Corso, W. Cooper J., Cumalat, J., Cushman, P., Da Via, C., Dazeley, S., Debbins, P., Deptuch, G., Dhawan, S., Di Benedetto, V., DiGiovene, B., Djurcic, Z., Dye, S., Elagin, A., Estrada, J., Evans, H., Etzion, E., Fast, J., Ferretti, C., Fisher, P., Fleming, B., Francis, K., Friedman, P., Frisch, H., Garcia-Sciveres, M., Gatto, C., Geronim, G., Gilchriese, G., Golwala, S., Grant, C., Grillo, A., Grünendahl, E., Gorham, P., Guan, L., Gutierrez, G., Haber, C., Hall, J., Haller, G., Hast, C., Heintz, U., Hemmick, T., Hitlin, D. G., Hogan, C., Hohlmann, M., Hoppe, E., Hsu, L., Huffer, M., Irwin, K., Izraelevitch, F., Jennings, G., Johnson, M., Jung, A., Kagan, H., Kenney, C., Kettell, S., Khanna, R., Khristenko, V., Krennrich, F., Kuehn, K., Kutschke, R., Learned, J., Lee, A. T., Levin, D., Liu, T., Liu, A. T. K., Lissauer, D., Love, J., Lynn, D., MacFarlane, D., Magill, S., Majewski, S., Mans, J., Maricic, J., Marleau, P., Mazzacane, A., McKinsey, D., Mehl, J., Mestvirisvilli, A., Meyer, S., Mokhov, N., Moshe, M., Mukherjee, A., Murat, P., Nahn, S., Narain, M., Nadel-Turonski, P., Newcomer, M., Nishimura, K., Nygren, D., Oberla, E., Onel, Y., Oreglia, M., Orrell, J., Paley, J., Para, A., Parker, S., Polychronakos, V., Pordes, S., Privitera, P., Prosser, A., Pyle, M., Raaf, J., Ramberg, E., Rameika, R., Rebel, B., Repond, J., Reyna, D., Ristori, L., Rivera, R., Ronzhin, A., Rusack, R., Russ, J., Ryd, A., Sadrozinski, H., Sahoo, H., Sanchez, M. C., Sanzeni, C., Schnetzer, S., Seidel, S., Seiden, A., Schmidt, I., Shenai, A., Shutt, T., Silver, Y., Smith, W., Snowden-Ifft, D., Sonnenschein, A., Southwick, D., Spiegel, L., Stanitzki, M., Striganov, S., Su, D., Sumner, R., Svoboda, R., Sweany, M., Talaga, R., Tayloe, R., Tentindo, S., Terentiev, N., Thom-Levy, J., Thorn, C., Tiffenberg, J., Trischuk, W., Tschirhart, R., Turner, M., Underwood, D., Uplegger, L., Urheim, J., Vagins, M., Van Bibber, K., Varner, G., Varner, R., Va'vra, J., Von der Lippe, H., Wagner, R., Wagner, S., Weaverdyck, C., Wenzel, H., Weinstein, A., Wetstein, M., White, A., Wigman, R., Wilson, P., Winn, D., Winter, P., Woody, C., Xia, L., Xie, J. Q., Ye, Z., Yeh, M. F., Yetkin, T., Yoo, J. H., Yu, J., Yu, J. M., Zeller, S., Zhang, J. L., Zhu, J. J., Zhou, B., Zhu, R. Y., and Zitzer, B.
Subjects: High Energy Physics - Experiment, High Energy Physics - Phenomenology, Physics - Instrumentation and Detectors
Abstract: These reports present the results of the 2013 Community Summer Study of the APS Division of Particles and Fields ("Snowmass 2013") on the future program of particle physics in the U.S. Chapter 8, on the Instrumentation Frontier, discusses the instrumentation needs of future experiments in the Energy, Intensity, and Cosmic Frontiers, promising new technologies for particle physics research, and issues of gathering resources for long-term research in this area., Comment: 50 pages
Published: 2014

47. Observations of the unidentified gamma-ray source TeV J2032+4130 by VERITAS

Author: VERITAS Collaboration, Aliu, E., Aune, T., Behera, B., Beilicke, M., Benbow, W., Berger, K., Bird, R., Buckley, J. H., Bugaev, V., Cardenzana, J. V, Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Duke, C., Dumm, J., Errando, M., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Hanna, D., Holder, J., Hughes, G., Humensky, T. B., Kargaltsev, O., Kaaret, P., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Lang, M. J., Madhavan, A. S, Maier, G., Majumdar, P., McCann, A., Moriarty, P., Mukherjee, R., Nieto, D., de Bhroithe, A. O'Faolain, Ong, R. A., Otte, A. N., Pandel, D., Perkins, J. S., Pohl, M., Popkow, A., Prokoph, H., Quinn, J., Ragan, K., Rajotte, J., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Sembroski, G. H., Skole, C., Staszak, D., Telezhinsky, I., Theiling, M., Tucci, J. V., Tyler, J., Varlotta, A., Vincent, S., Wakely, S. P., Weekes, T. C., Weinstein, A., Welsing, R., Williams, D. A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: TeV J2032+4130 was the first unidentified source discovered at very high energies (VHE; E $>$ 100 GeV), with no obvious counterpart in any other wavelength. It is also the first extended source to be observed in VHE gamma rays. Following its discovery, intensive observational campaigns have been carried out in all wavelengths in order to understand the nature of the object, which have met with limited success. We report here on a deep observation of TeV J2032+4130, based on 48.2 hours of data taken from 2009 to 2012 by the VERITAS (Very Energetic Radiation Imaging Telescope Array System) experiment. The source is detected at 8.7 standard deviations ($\sigma$) and is found to be extended and asymmetric with a width of 9.5$^{\prime}$$\pm$1.2$^{\prime}$ along the major axis and 4.0$^{\prime}$$\pm$0.5$^{\prime}$ along the minor axis. The spectrum is well described by a differential power law with an index of 2.10 $\pm$ 0.14$_{stat}$ $\pm$ 0.21$_{sys}$ and a normalization of (9.5 $\pm$ 1.6$_{stat}$ $\pm$ 2.2$_{sys}$) $\times$ 10$^{-13}$TeV$^{-1}$ cm$^{-2}$ s$^{-1}$ at 1 TeV. We interpret these results in the context of multiwavelength scenarios which particularly favor the pulsar wind nebula (PWN) interpretation.
Published: 2014
Full Text: View/download PDF

48. A Three-Year Multi-Wavelength Study of the Very High Energy Gamma-ray Blazar 1ES 0229+200

Author: Aliu, E., Archambault, S., Arlen, T., Aune, T., Behera, B., Beilicke, M., Benbow, W., Berger, K., Bird, R., Bouvier, A., Buckley, J. H., Bugaev, V., Byrum, K., Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Duke, C., Dumm, J., Errando, M., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fleischhack, H., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Hanna, D., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., Madhavan, A. S, Maier, G., Majumdar, P., McArthur, S., McCann, A., Meagher, K., Millis, J., Moriarty, P., Mukherjee, R., Nieto, D., de Bhroithe, A. O'Faolain, Ong, R. A., Otte, A. N., Park, N., Perkins, J. S., Pohl, M., Popkow, A., Prokoph, H., Quinn, J., Ragan, K., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Sembroski, G. H., Smith, A. W., Staszak, D., Telezhinsky, I., Theiling, M., Varlotta, A., Vassiliev, V. V., Vincent, S., Wakely, S. P., Weekes, T. C., Weinstein, A., Welsing, R., Williams, D. A., Zajczyk, A., and Zitzer, B.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: The high-frequency-peaked BL Lacertae object 1ES 0229+200 is a relatively distant (z = 0.1396), hard-spectrum (Gamma ~ 2.5), very-high-energy-emitting (E > 100 GeV) gamma-ray blazar. Very-high-energy measurements of this active galactic nucleus have been used to place constraints on the intensity of the extragalactic background light and the intergalactic magnetic field. A multi-wavelength study of this object centered around very-high-energy observations by VERITAS is presented. This study obtained, over a period of three years, an 11.7 standard deviation detection and an average integral flux F(E>300 GeV) = (23.3 +- 2.8_stat +- 5.8_sys) x 10^-9 photons m^-2 s^-1, or 1.7% of the Crab Nebula's flux (assuming the Crab Nebula spectrum measured by H.E.S.S). Supporting observations from Swift and RXTE are analyzed. The Swift observations are combined with previously published Fermi observations and the very-high-energy measurements to produce an overall spectral energy distribution which is then modeled assuming one-zone synchrotron-self-Compton emission. The chi^2 probability of the TeV flux being constant is 1.6%. This, when considered in combination with measured variability in the X-ray band, and the demonstrated variability of many TeV blazars, suggests that the use of blazars such as 1ES 0229+200 for intergalactic magnetic field studies may not be straightforward and challenges models that attribute hard TeV spectra to secondary gamma-ray production along the line of sight., Comment: Accepted for publication in ApJ
Published: 2013
Full Text: View/download PDF

49. Long-term TeV and X-ray Observations of the Gamma-ray Binary HESS J0632+057

Author: VERITAS Collaboration, Aliu, E., Archambault, S., Aune, T., Behera, B., Beilicke, M., Benbow, W., Berger, K., Bird, R., Bouvier, A., Buckley, J. H., Bugaev, V., Byrum, K., Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Duke, C., Dumm, J., Errando, M., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fortin, P., Fortson, L., Furniss, A., Galante, N., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Hanna, D., Holder, J., Hughes, G., Humensky, T. B., Kaaret, P., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Krennrich, F., Lang, M. J., Madhavan, A. S, Maier, G., Majumdar, P., McCann, A., Moriarty, P., Mukherjee, R., Nieto, D., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Park, N., Perkins, J. S., Pohl, M., Popkow, A., Prokoph, H., Quinn, J., Ragan, K., Rajotte, J., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Rousselle, J., Sembroski, G. H., Sheidaei, F., Skole, C., Smith, A. W., Staszak, D., Stroh, M., Telezhinsky, I., Theiling, M., Tucci, J. V., Tyler, J., Varlotta, A., Vincent, S., Wakely, S. P., Weinstein, A., Welsing, R., Williams, D. A., Zajczyk, A., Zitzer, B., Collaboration, H. E. S. S., Abramowski, A., Aharonian, F., Benkhali, F. Ait, Akhperjanian, A. G., Angüner, E., Anton, G., Balenderan, S., Balzer, A., Barnacka, A., Becherini, Y., Tjus, J. Becker, Bernlöhr, K., Birsin, E., Bissaldi, E., Biteau, J., Böttcher, M., Boisson, C., Bolmont, J., Bordas, P., Brucker, J., Brun, F., Brun, P., Bulik, T., Carrigan, S., Casanova, S., Chadwick, P. M., Chalme-Calvet, R., Chaves, R. C. G., Cheesebrough, A., Chrétien, M., Colafrancesco, S., Cologna, G., Conrad, J., Couturier, C., Dalton, M., Daniel, M. K., Davids, I. D., Degrange, B., Deil, C., deWilt, P., Dickinson, H. J., Djannati-Ataï, A., Domainko, W., Drury, L. O'C., Dubus, G., Dutson, K., Dyks, J., Dyrda, M., Edwards, T., Egberts, K., Eger, P., Espigat, P., Farnier, C., Fegan, S., Feinstein, F., Fernandes, M. V., Fernandez, D., Fiasson, A., Fontaine, G., Forster, A., Füßling, M., Gajdus, M., Gallant, Y. A., Garrigoux, T., Giavitto, G., Giebels, B., Glicenstein, J. F., Grondin, M. -H., Grudzińska, M., Häffner, S., Hahn, J., Harris, J., Heinzelmann, G., Henri, G., Hermann, G., Hervet, O., Hillert, A., Hinton, J. A., Hofmann, W., Hofverberg, P., Holler, M., Horns, D., Jacholkowska, A., Jahn, C., Jamrozy, M., Janiak, M., Jankowsky, F., Jung, I., Kastendieck, M. A., Katarzyński, K., Katz, U., Kaufmann, S., Khélifi, B., Kieffer, M., Klepser, S., Klochkov, D., Kluźniak, W., Kneiske, T., Kolitzus, D., Komin, Nu., Kosack, K., Krakau, S., Krayzel, F., Krüger, P. P., Laffon, H., Lamanna, G., Lefaucheur, J., Lemiére, A., Lemoine-Goumard, M., Lenain, J. -P., Lennarz, D., Lohse, T., Lopatin, A., Lu, C. -C., Marandon, V., Marcowith, A., Marx, R., Maurin, G., Maxted, N., Mayer, M., McComb, T. J. L., Méhault, J., Menzler, U., Meyer, M., Moderski, R., Mohamed, M., Moulin, E., Murach, T., Naumann, C. L., de Naurois, M., Niemiec, J., Nolan, S. J., Oakes, L., Ohm, S., Wilhelmi, E. de Onña, Opitz, B., Ostrowski, M., Oya, I., Panter, M., Parsons, R. D., Arribas, M. Paz, Pekeur, N. W., Pelletier, G., Perez, J., Petrucci, P. -O., Peyaud, B., Pita, S., Poon, H., Pühlhofer, G., Punch, M., Quirrenbach, A., Raab, S., Raue, M., Reimer, A., Reimer, O., Renaud, M., Reyes, R. de los, Rieger, F., Rob, L., Romoli, C., Rosier-Lees, S., Rowell, G., Rudak, B., Rulten, C. B., Sahakian, V., Sanchez, D. A., Santangelo, A., Schlickeiser, R., Schüssler, F., Schulz, A., Schwanke, U., Schwarzburg, S., Schwemmer, S., Sol, H., Spengler, G., Spies, F., Stawarz, Ł., Steenkamp, R., Stegmann, C., Stinzing, F., Stycz, K., Sushch, I., Szostek, A., Tavernet, J. -P., Tavernier, T., Taylor, A. M., Terrier, R., Tluczykont, M., Trichard, C., Valerius, K., van Eldik, C., Vasileiadis, G., Venter, C., Viana, A., Vincent, P., Völk, H. J., Volpe, F., Vorster, M., Wagner, S. J., Wagner, P., Ward, M., Weidinger, M., Weitzel, Q., White, R., Wierzcholska, A., Willmann, P., Wörnlein, A., Wouters, D., Zacharias, M., Zdziarski, A. A., Zech, A., and Zechlin, H. -S.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: HESS J0632+057 is the only gamma-ray binary known so far whose position in the sky allows observations with ground-based observatories both in the northern and southern hemispheres. Here we report on long-term observations of HESS J0632+057 conducted with the VERITAS and H.E.S.S. Cherenkov Telescopes and the X-ray Satellite Swift, spanning a time range from 2004 to 2012 and covering most of the system's orbit. The VHE emission is found to be variable, and is correlated with that at X-ray energies. An orbital period of $315 ^{+6}_{-4}$ days is derived from the X-ray data set, which is compatible with previous results, $P = (321 \pm 5$) days. The VHE light curve shows a distinct maximum at orbital phases close to 0.3, or about 100 days after periastron passage, which coincides with the periodic enhancement of the X-ray emission. Furthermore, the analysis of the TeV data shows for the first time a statistically significant ($> 6.5 \sigma$) detection at orbital phases 0.6--0.9. The obtained gamma-ray and X-ray light curves and the correlation of the source emission at these two energy bands are discussed in the context of the recent ephemeris obtained for the system. Our results are compared to those reported for other gamma-ray binaries., Comment: 35 pages, 8 figures, accepted for publication in ApJ
Published: 2013
Full Text: View/download PDF

50. VERITAS Observations of the Microquasar Cygnus X-3

Author: Archambault, S., Beilicke, M., Benbow, W., Berger, K., Bird, R., Bouvier, A., Buckley, J. H., Bugaev, V., Byrum, K., Cerruti, M., Chen, X., Ciupik, L., Connolly, M. P., Cui, W., Duke, C., Dumm, J., Errando, M., Falcone, A., Federici, S., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Galante, N., Gillanders, G. H., Griffin, S., Griffiths, S. T., Grube, J., Gyuk, G., Hanna, D., Holder, J., Hughes, G., Humensky, T. B., Kaaret, P., Kertzman, M., Khassen, Y., Kieda, D., Krawczynski, H., Lang, M. J., Madhavan, A. S, Maier, G., Majumdar, P., McArthur, S., McCann, A., Moriarty, P., Mukherjee, R., Nieto, D., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Pandel, D., Park, N., Perkins, J. S., Pohl, M., Popkow, A., Prokoph, H., Quinn, J., Ragan, K., Rajotte, J., Reyes, L. C., Reynolds, P. T., Richards, G. T., Roache, E., Sembroski, G. H., Sheidaei, F., Smith, A. W., Staszak, D., Telezhinsky, I., Theiling, M., Tucci, J. V., Tyler, J., Varlotta, A., Vincent, S., Wakely, S. P., Weekes, T. C., Weinstein, A., Williams, D. A., Zitzer, B., and McCollough, M. L.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report results from TeV gamma-ray observations of the microquasar Cygnus X-3. The observations were made with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) over a time period from 2007 June 11 to 2011 November 28. VERITAS is most sensitive to gamma rays at energies between 85 GeV to 30 TeV. The effective exposure time amounts to a total of about 44 hours, with the observations covering six distinct radio/X-ray states of the object. No significant TeV gamma-ray emission was detected in any of the states, nor with all observations combined. The lack of a positive signal, especially in the states where GeV gamma rays were detected, places constraints on TeV gamma-ray production in Cygnus X-3. We discuss the implications of the results., Comment: 23 pages, 4 figures, 3 tables, accepted for publication in ApJ
Published: 2013
Full Text: View/download PDF

Catalog

Books, media, physical & digital resources

See catalog results

Searchworks

Select search scope, currently: Articles Catalog books, media & more in Jio Institute collections Articles journal articles & other e-resources

Search

Search Constraints

Refine your results

Search Limiters

Topic

Publication Year Range

Language

Publication Type

Journal

Database

Publisher

555 results on '"Zitzer, B"'

Search Results

Catalog

Select search scope, currently: Articles

Catalog

books, media & more in Jio Institute collections

Articles

journal articles & other e-resources