Search

Your search keyword '"Fortson L."' showing total 1,080 results
Start Over Author "Fortson L."
1,080 results on '"Fortson L."'

1. An indirect search for dark matter with a combined analysis of dwarf spheroidal galaxies from VERITAS

Author

Acharyya, A., Adams, C. B., Bangale, P., Bartkoske, J. T., Batista, P., Benbow, W., Christiansen, J. L., Chromey, A. J., Duerr, A., Errando, M., Falcone, A., Feng, Q., Foote, G. M., Fortson, L., Furniss, A., Hanlon, W., Hanna, D., Hervet, O., Hinrichs, C. E., Holder, J., Humensky, T. B., Jin, W., Johnson, M. N., Kaaret, P., Kertzman, M., Kieda, D., Kleiner, T. K., Korzoun, N., Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, Conor E., Millard, M. J., Mooney, C. L., Moriarty, P., Mukherjee, R., Ning, W., O'Brien, S., Ong, R. A., Park, N., Pohl, M., Pueschel, E., Quinn, J., Rabinowitz, P. L., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Ryan, J. L., Sadeh, I., Saha, L., Sembroski, G. H., Shang, R., Splettstoesser, M., Tak, Donggeun, Talluri, A. K., Tucci, J. V., Vassiliev, V. V., Weinstein, A., Williams, D. A., and Wong, S. L.

Subjects
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract

Understanding the nature and identity of dark matter is a key goal in the physics community. In the case that TeV-scale dark matter particles decay or annihilate into standard model particles, very-high-energy (VHE) gamma rays (greater than 100 GeV) will be present in the final state. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is an imaging atmospheric Cherenkov telescope array that can indirectly detect VHE gamma rays in an energy range of 100 GeV to > 30 TeV. Dwarf spheroidal galaxies (dSphs) are ideal candidates in the search for dark matter due to their high dark matter content, high mass-to-light ratios, and their low gamma-ray fluxes from astrophysical processes. This study uses a legacy data set of 638 hours collected on 17 dSphs, built over 11 years with an observing strategy optimized according to the dark matter content of the targets. The study addresses a broad dark matter particle mass range, extending from 200 GeV to 30 PeV. In the absence of a detection, we set the upper limits on the dark matter velocity-weighted annihilation cross section., Comment: 18 pages, 7 figures, 3 tables, accepted in PRD

Published
2024

2. A multi-wavelength study to decipher the 2017 flare of the blazar OJ 287

Author

Acharyya, A., Adams, C. B., Archer, A., Bangale, P., Bartkoske, J. T., Batista, P., Benbow, W., Brill, A., Caldwell, J. P., Carini, M., Christiansen, J. L., Chromey, A. J., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Foote, J., Fortson, L., Furniss, A., Gallagher, G., Hanlon, W., Hanna, D., Hervet, O., Hinrichs, C. E., Hoang, J., Holder, J., Humensky, T. B., Jin, W., Johnson, M. N., Kaaret, P., Kertzman, M., Kherlakian, M., Kieda, D., Kleiner, T. K., Korzoun, N., Krennrich, F., Kumar, S., Lang, M. J., Lundy, M., Maier, G., EMcGrath, C., Millard, M. J., Millis, J., Mooney, C. L., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Pohl, M., Pueschel, E., Quinn, J., Rabinowitz, P. L., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Ryan, J. L., Sadeh, I., Sadun, A. C., Saha, L., Santander, M., Sembroski, G. H., Shahinyan, K., Shang, R., Splettstoesser, M., Tak, D., Talluri, A. K., Tucci, J. V., Williams, D. A., Wong, S. L., Jorstad, S. G., Lico, R., Lusen, P., and Marscher, A. P.

Subjects
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract

In February 2017, the blazar OJ~287 underwent a period of intense multiwavelength activity. It reached a new historic peak in the soft X-ray (0.3-10 keV) band, as measured by Swift-XRT. This event coincides with a very-high-energy (VHE) $\gamma$-ray outburst that led VERITAS to detect emission above 100 GeV, with a detection significance of $10\sigma$ (from 2016 December 9 to 2017 March 31). The time-averaged VHE $\gamma$-ray spectrum was consistent with a soft power law ($\Gamma = -3.81 \pm 0.26$) and an integral flux corresponding to $\sim2.4\%$ that of the Crab Nebula above the same energy. Contemporaneous data from multiple instruments across the electromagnetic spectrum reveal complex flaring behavior, primarily in the soft X-ray and VHE bands. To investigate the possible origin of such an event, our study focuses on three distinct activity states: before, during, and after the February 2017 peak. The spectral energy distributions during these periods suggest the presence of at least two non-thermal emission zones, with the more compact one responsible for the observed flare. Broadband modeling results and observations of a new radio knot in the jet of OJ~287 in 2017 are consistent with a flare originating from a strong recollimation shock outside the radio core., Comment: 21 pages, 7 figures, accepted for publication in The Astrophysical Journal

Published
2024

3. VERITAS contributions to the 38th International Cosmic Ray Conference

Author

Acharyya, A., Adams, C. B., Archer, A., Bangale, P., Bartkoske, J. T., Batista, P., Benbow, W., Christiansen, J. L., Chromey, A. J., Duerr, A., Errando, M., Feng, Q., Foote, G. M., Fortson, L., Furniss, A., Hanlon, W., Hervet, O., Hinrichs, C. E., Hoang, J., Holder, J., Hughes, Z., Humensky, T. B., Jin, W., Johnson, M. N., Kertzman, M., Kherlakian, M., Kieda, D., Kleiner, T. K., Korzoun, N., Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E, Millard, M. J., Mooney, C. L., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Park, N., Poggemann, C., Pohl, M., Pueschel, E., Quinn, J., Rabinowitz, P. L., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Ryan, J. L., Sadeh, I., Saha, L., Santander, M., Sembroski, G. H., Shang, R., Splettstoesser, M., Talluri, A. K., Tucci, J. V., Vassiliev, V. V., Weinstein, A., Williams, D. A., Wong, S. L., and Woo, J.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

Compilation of papers presented by the VERITAS Collaboration at the 38th International Cosmic Ray Conference (ICRC), held July 26 through August 3, 2023 in Nagoya, Japan., Comment: html page. ICRC 2023, Nagoya, Japan

Published
2023

4. Solar Jet Hunter: a citizen science initiative to identify coronal jets in EUV data sets

Author

Musset, S., Jol, P., Sankar, R., Alnahari, S., Kapsiak, C., Ostlund, E., Lasko, K., Glesener, L., Fortson, L., Fleishman, G. D., Panesar, N. K., Zhang, Y., Jeunon, M., and Hurlburt, N.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Context. Solar coronal jets seen in EUV are ubiquitous on the Sun, have been found in and at the edges of active regions, at the boundaries of coronal holes, and in the quiet Sun. Jets have various shapes, sizes, brightness, velocities and duration in time, which complicates their detection by automated algorithms. So far, solar jets reported in the Heliophysics Event Knowledgebase (HEK) have been mostly reported by humans looking for them in the data, with different levels of precision regarding their timing and positions. Aims. We create a catalogue of solar jets observed in EUV at 304 {\AA} containing precise and consistent information on the jet timing, position and extent. Methods. We designed a citizen science project, "Solar Jet Hunter", on the Zooniverse platform, to analyze EUV observations at 304 {\AA} from the Solar Dynamic Observatory/Atmospheric Imaging Assembly (SDO/AIA). We created movie strips for regions of the Sun in which jets have been reported in HEK and ask the volunteers to 1) confirm the presence of at least one jet in the data and 2) report the timing, position and extent of the jet. Results. We report here the design of the project and the results obtained after the analysis of data from 2011 to 2016. 365 "coronal jet" events from HEK served as input for the citizen science project, equivalent to more than 120,000 images distributed into 9,689 "movie strips". Classification by the citizen scientists resulted with only 21% of the data containing a jet, and 883 individual jets being identified. Conclusions. We demonstrate how citizen science can enhance the analysis of solar data with the example of Solar Jet Hunter. The catalogue of jets thus created is publicly available and will enable statistical studies of jets and related phenomena. This catalogue will also be used as a training set for machines to learn to recognize jets in further data sets.

Published
2023
Full Text
View/download PDF

5. Long-term monitoring of the radio-galaxy M87 in gamma-rays: joint analysis of MAGIC, VERITAS and Fermi-LAT data

Author

Molero, M., Batista, P., Fortson, L., Rosillo, M. Nievas, Pueschel, E., Ribeiro, D., and Acosta, M. Vázquez

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

M87 was discovered in the very-high-energy band (VHE, E > 100 GeV) with HEGRA in 2003, long before its emission was detected in the high-energy band (HE, E > 100 MeV) with Fermi-LAT in 2009, opening the window to a new family of extragalactic sources with tilted jets. After a series of major VHE flares in 2005, 2008, and 2010, which were detected in multiple bands, the source has been found in a low activity state, interrupted only by comparatively smaller-scale flares. MAGIC and VERITAS, two stereoscopic Cherenkov telescope arrays located at Roque de los Muchachos Observatory (Canary Islands, Spain) and the Fred Lawrence Whipple Observatory (Arizona, US), have monitored M87 continuously and in coordination for more than 10 years. In this work, we present the data for 4 years of MAGIC and VERITAS observations corresponding to 2019, 2020, 2021 and 2022. The resulting light curves are shown in daily and monthly scales where no significant variability is observed. In addition, we show the first joint analysis using combined event data from the two VHE instruments and Fermi-LAT to compute the spectral energy distribution.

Published
2023

6. Multiwavelength Observations of the Blazar PKS 0735+178 in Spatial and Temporal Coincidence with an Astrophysical Neutrino Candidate IceCube-211208A

Author

Acharyya, A., Adams, C. B., Archer, A., Bangale, P., Bartkoske, J. T., Batista, P., Benbow, W., Brill, A., Buckley, J. H., Christiansen, J. L., Chromey, A. J., Errando, M., Falcone, A., Feng, Q., Foote, G. M., Fortson, L., Furniss, A., Gallagher, G., Hanlon, W., Hanna, D., Hervet, O., Hinrichs, C. E., Hoang, J., Holder, J., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kherlakian, M., Kieda, D., Kleiner, T. K., Korzoun, N., Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E, Millard, M. J., Millis, J., Mooney, C. L., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Sadeh, I., Sadun, A. C., Saha, L., Santander, M., Sembroski, G. H., Shang, R., Splettstoesser, M., Talluri, A. Kaushik, Tucci, J. V., Vassiliev, V. V., Weinstein, A., Williams, D. A., Wong, S. L., Woo, J., Aharonian, F., Aschersleben, J., Backes, M., Martins, V. Barbosa, Batzofin, R., Becherini, Y., Berge, D., Bernlohr, K., Bi, B., Bottcher, M., Boisson, C., Bolmont, J., de Lavergne, M. de Bony, Borowska, J., Bouyahiaoui, M., Bradascio, F., Breuhaus, M., Brose, R., Brun, F., Bruno, B., Bulik, T., Burger-Scheidlin, C., Caroff, S., Casanova, S., Cecil, R., Celic, J., Cerruti, M., Chand, T., Chandra, S., Chen, A., Chibueze, J., Chibueze, O., Cotter, G., Dai, S., Mbarubucyeye, J. Damascene, Djannati-Atai, A., Dmytriiev, A., Doroshenko, V., Einecke, S., Ernenwein, J. -P., de Clairfontaine, G. Fichet, Filipovic, M., Fontaine, G., Fussling, M., Funk, S., Gabici, S., Ghafourizadeh, S., Giavitto, G., Glawion, D., Glicenstein, J. F., Goswami, P., Grolleron, G., Haerer, L., Hinton, J. A., Holch, T. L., Holler, M., Horns, D., Jamrozy, M., Jankowsky, F., Joshi, V., Jung-Richardt, I., Kasai, E., Katarzynski, K., Khatoon, R., Khelifi, B., Klepser, S., Kluzniak, W., Kosack, K., Kostunin, D., Lang, R. G., Stum, S. Le, Lemiere, A., Lenain, J. P., Leuschner, F., Lohse, T., Luashvili, A., Lypova, I., Mackey, J., Malyshev, D., Marandon, V., Marchegiani, P., Marcowith, A., Marti-Devesa, G., Marx, R., Mitchell, A., Moderski, R., Mohrmann, L., Montanari, A., Moulin, E., Murach, T., Nakashima, K., Niemiec, J., Noel, A. Priyana, O'Brien, P., Olivera-Nieto, L., Wilhelmi, E. de Ona, Ostrowski, M., Panny, S., Panter, M., Peron, G., Prokhorov, D. A., Puhlhofer, G., Punch, M., Quirrenbach, A., Reichherzer, P., Reimer, A., Reimer, O., Ren, H., Renaud, M., Rieger, F., Rudak, B., Ruiz-Velasco, E., Sahakian, V., Santangelo, A., Sasaki, M., Schafer, J., Schussler, F., Schutte, H. M., Schwanke, U., Shapopi, J. N. S., Specovius, A., Spencer, S., Stawarz, L., Steenkamp, R., Steinmassl, S., Sushch, I., Suzuki, H., Takahashi, T., Tanaka, T., Terrier, R., van Eldik, C., Vecchi, M., Veh, J., Venter, C., Vink, J., White, R., Wierzcholska, A., Wong, Yu Wun, Zacharias, M., Zargaryan, D., Zdziarski, A. A., Zech, A., Zouari, S., Zywucka, N., and Mori, K.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We report on multiwavelength target-of-opportunity observations of the blazar PKS 0735+178, located 2.2$^\circ$ away from the best-fit position of the IceCube neutrino event IceCube-211208A detected on December 8, 2021. The source was in a high-flux state in the optical, ultraviolet, X-ray, and GeV gamma-ray bands around the time of the neutrino event, exhibiting daily variability in the soft X-ray flux. The X-ray data from Swift-XRT and NuSTAR characterize the transition between the low-energy and high-energy components of the broadband spectral energy distribution (SED), and the gamma-ray data from Fermi -LAT, VERITAS, and H.E.S.S. require a spectral cut-off near 100 GeV. Both X-ray and gamma-ray measurements provide strong constraints on the leptonic and hadronic models. We analytically explore a synchrotron self-Compton model, an external Compton model, and a lepto-hadronic model. Models that are entirely based on internal photon fields face serious difficulties in matching the observed SED. The existence of an external photon field in the source would instead explain the observed gamma-ray spectral cut-off in both leptonic and lepto-hadronic models and allow a proton jet power that marginally agrees with the Eddington limit in the lepto-hadronic model. We show a numerical lepto-hadronic model with external target photons that reproduces the observed SED and is reasonably consistent with the neutrino event despite requiring a high jet power., Comment: 21 pages, 3 figures, accepted by ApJ

Published
2023

7. Search for Ultraheavy Dark Matter from Observations of Dwarf Spheroidal Galaxies with VERITAS

Author

Acharyya, A., Archer, A., Bangale, P., Bartkoske, J. T., Batista, P., Baumgart, M., Benbow, W., Buckley, J. H., Falcone, A., Feng, Q., Finley, J. P., Foote, G. M., Fortson, L., Furniss, A., Gallagher, G., Hanlon, W. F., Hervet, O., Hoang, J., Holder, J., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kherlakian, M., Kieda, D., Kleiner, T. K., Korzoun, N., Krennrich, F., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E, Moriarty, P., O'Brien, S., Ong, R. A., Pfrang, K., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Roache, E., Rodd, N. L., Ryan, J. L., Sadeh, I., Saha, L., Santander, M., Sembroski, G. H., Shang, R., Splettstoesser, M., Tak, D., Tucci, J. V., Vassiliev, V. V., and Williams, D. A.

Subjects
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract

Dark matter is a key piece of the current cosmological scenario, with weakly interacting massive particles (WIMPs) a leading dark matter candidate. WIMPs have not been detected in their conventional parameter space (100 GeV $\lesssim M_{\chi} \lesssim$ 100 TeV), a mass range accessible with current Imaging Atmospheric Cherenkov Telescopes. As ultraheavy dark matter (UHDM; $M_{\chi} \gtrsim$ 100 TeV) has been suggested as an under-explored alternative to the WIMP paradigm, we search for an indirect dark matter annihilation signal in a higher mass range (up to 30 PeV) with the VERITAS gamma-ray observatory. With 216 hours of observations of four dwarf spheroidal galaxies, we perform an unbinned likelihood analysis. We find no evidence of a $\gamma$-ray signal from UHDM annihilation above the background fluctuation for any individual dwarf galaxy nor for a joint-fit analysis, and consequently constrain the velocity-weighted annihilation cross section of UHDM for dark matter particle masses between 1 TeV and 30 PeV. We additionally set constraints on the allowed radius of a composite UHDM particle., Comment: 10 pages, 7 figures

Published
2023
Full Text
View/download PDF

8. VERITAS and Fermi-LAT constraints on the Gamma-ray Emission from Superluminous Supernovae SN2015bn and SN2017egm

Author

Acharyya, A., Adams, C. B., Bangale, P., Benbow, W., Buckley, J. H., Capasso, M., Dwarkadas, V. V., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Foote, G. M., Fortson, L., Furniss, A., Gallagher, G., Gent, A., Hanlon, W. F, Hervet, O., Holder, J., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kherlakian, M., Kieda, D., Kleiner, T. K, Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E, Millis, J., Moriarty, P., Mukherjee, R., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Patel, S. R., Pfrang, K., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Ryan, J. L., Sadeh, I., Santander, M., Sembroski, G. H., Shang, R., Splettstoesser, M., Tak, D., Tucci, J. V., Weinstein, A., Williams, D. A., Metzger, B. D., Nicholl, M., and Vurm, I.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

Superluminous supernovae (SLSNe) are a rare class of stellar explosions with luminosities ~10-100 times greater than ordinary core-collapse supernovae. One popular model to explain the enhanced optical output of hydrogen-poor (Type I) SLSNe invokes energy injection from a rapidly spinning magnetar. A prediction in this case is that high-energy gamma rays, generated in the wind nebula of the magnetar, could escape through the expanding supernova ejecta at late times (months or more after optical peak). This paper presents a search for gamma-ray emission in the broad energy band from 100 MeV to 30 TeV from two Type I SLSNe, SN2015bn, and SN2017egm, using observations from Fermi-LAT and VERITAS. Although no gamma-ray emission was detected from either source, the derived upper limits approach the putative magnetar's spin-down luminosity. Prospects are explored for detecting very-high-energy (VHE; 100 GeV - 100 TeV) emission from SLSNe-I with existing and planned facilities such as VERITAS and CTA., Comment: 20 pages, 7 figures, 2 tables

Published
2023
Full Text
View/download PDF

9. VTSCat: The VERITAS Catalog of Gamma-Ray Observations

Author

Acharyya, A., Adams, C. B., Archer, A., Bangale, P., Bartkoske, J. T., Batista, P., Benbow, W., Buckley, J. H., Brill, A., Capasso, M., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Errando, M., Falcone, A., Farrell, K. A, Feng, Q., Finley, J. P., Foote, G. M, Fortson, L., Furniss, A., Gallagher, G., Gent, A., Giuri, C., Gueta, O., Hanlon, W. F, Hanna, D., Hassan, T., Hervet, O., Hoang, J., Holder, J., Hughes, G., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kieda, D., Kleiner, T. K., Korzoun, N., Krennrich, F., Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E, Millard, M. J, Mooney, C. L., Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Pandel, D., Park, N., Patel, S. R., Patel, S., Pfrang, K., Pichel, A., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Richards, G. T., Roache, E., Rovero, A. C., Rulten, C., Ryan, J. L., Sadeh, I., Santander, M., Schlenstedt, S., Sembroski, G. H., Shang, R., Splettstoesser, M., Stevenson, B., Tak, D., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Williams, D. A., Williamson, T. J, Angelini, L., Basu-Zych, A., Sabol, E., and Smale, A.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The ground-based gamma-ray observatory VERITAS (Very Energetic Radiation Imaging Telescope Array System) is sensitive to photons of astrophysical origin with energies in the range between $\approx 85$ GeV to $\approx 30$ TeV. The instrument consists of four 12-m diameter imaging Cherenkov telescopes operating at the Fred Lawrence Whipple Observatory (FLWO) in southern Arizona. VERITAS started four-telescope operations in 2007 and collects about 1100 hours of good-weather data per year. The VERITAS collaboration has published over 100 journal articles since 2008 reporting on gamma-ray observations of a large variety of objects: Galactic sources like supernova remnants, pulsar wind nebulae, and binary systems; extragalactic sources like star forming galaxies, dwarf-spheroidal galaxies, and highly-variable active galactic nuclei. This note presents VTSCat: the catalog of high-level data products from all VERITAS publications., Comment: Version with corrected author list

Published
2023
Full Text
View/download PDF

10. Search for Ultraheavy Dark Matter from Observations of Dwarf Spheroidal Galaxies with VERITAS

Author

Acharyya, A, Archer, A, Bangale, P, Bartkoske, JT, Batista, P, Baumgart, M, Benbow, W, Buckley, JH, Falcone, A, Feng, Q, Finley, JP, Foote, GM, Fortson, L, Furniss, A, Gallagher, G, Hanlon, WF, Hervet, O, Hoang, J, Holder, J, Humensky, TB, Jin, W, Kaaret, P, Kertzman, M, Kherlakian, M, Kieda, D, Kleiner, TK, Korzoun, N, Krennrich, F, Lang, MJ, Lundy, M, Maier, G, McGrath, CE, Moriarty, P, O’Brien, S, Ong, RA, Pfrang, K, Pohl, M, Pueschel, E, Quinn, J, Ragan, K, Reynolds, PT, Roache, E, Rodd, NL, Ryan, JL, Sadeh, I, Saha, L, Santander, M, Sembroski, GH, Shang, R, Splettstoesser, M, Tak, D, Tucci, JV, Vassiliev, VV, and Williams, DA

Subjects
Nuclear and Plasma Physics, Particle and High Energy Physics, Physical Sciences, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics, Astronomical sciences, Particle and high energy physics, Space sciences
Abstract

Dark matter is a key piece of the current cosmological scenario, with weakly interacting massive particles (WIMPs) a leading dark matter candidate. WIMPs have not been detected in their conventional parameter space (100 GeV ≲M χ ≲ 100 TeV), a mass range accessible with current Imaging Atmospheric Cherenkov Telescopes. As ultraheavy dark matter (UHDM; M χ ≳ 100 TeV) has been suggested as an underexplored alternative to the WIMP paradigm, we search for an indirect dark matter annihilation signal in a higher mass range (up to 30 PeV) with the VERITAS γ-ray observatory. With 216 hr of observations of four dwarf spheroidal galaxies, we perform an unbinned likelihood analysis. We find no evidence of a γ-ray signal from UHDM annihilation above the background fluctuation for any individual dwarf galaxy nor for a joint-fit analysis, and consequently constrain the velocity-weighted annihilation cross section of UHDM for dark matter particle masses between 1 TeV and 30 PeV. We additionally set constraints on the allowed radius of a composite UHDM particle.

Published
2023

11. Gamma-ray observations of MAXI J1820+070 during the 2018 outburst

Author

Abe, H., Abe, S., Acciari, V. A., Aniello, T., Ansoldi, S., Antonelli, L. A., Engels, A. Arbet, Arcaro, C., Artero, M., Asano, K., Baack, D., Babić, A., Baquero, A., de Almeida, U. Barres, Barrio, J. A., Batković, I., Baxter, J., González, J. Becerra, Bednarek, W., Bernardini, E., Bernardos, M., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Bošnjak, Ž., Burelli, I., Busetto, G., Carosi, R., Carretero-Castrillo, M., Ceribella, G., Chai, Y., Chilingarian, A., Cikota, S., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Amico, G., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Del Popolo, A., Delfino, M., Delgado, J., Mendez, C. Delgado, Depaoli, D., Di Pierro, F., Di Venere, L., Prester, D. Dominis, Donini, A., Dorner, D., Doro, M., Elsaesser, D., Emery, G., Ramazani, V. Fallah, Fariña, L., Fattorini, A., Font, L., Fruck, C., Fukami, S., Fukazawa, Y., López, R. J. García, Garczarczyk, M., Gasparyan, S., Gaug, M., Paiva, J. G. Giesbrecht, Giglietto, N., Giordano, F., Gliwny, P., Godinović, N., Grau, R., Green, D., Green, J. G., Hadasch, D., Hahn, A., Hassan, T., Heckmann, L., Herrera, J., Hoang, J., Hrupec, D., Hütten, M., Imazawa, R., Inada, T., Iotov, R., Ishio, K., Martínez, I. Jiménez, Jormanainen, J., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Linhoff, L., Lombardi, S., Longo, F., López-Coto, R., López-Moya, M., López-Oramas, A., Loporchio, S., Lorini, A., Lyard, E., Fraga, B. Machado de Oliveira, Majumdar, P., Makariev, M., Maneva, G., Mang, N., Manganaro, M., Mangano, S., Mannheim, K., Mariotti, M., Martínez, M., Aguilar, A. Mas, Mazin, D., Menchiari, S., Mender, S., Mićanović, S., Miceli, D., Miener, T., Miranda, J. M., Mirzoyan, R., Molina, E., Mondal, H. A., Moralejo, A., Morcuende, D., Moreno, V., Nakamori, T., Nanci, C., Nava, L., Neustroev, V., Rosillo, M. Nievas, Nigro, C., Nilsson, K., Nishijima, K., Ekoume, T. Njoh, Noda, K., Nozaki, S., Ohtani, Y., Oka, T., Okumura, A., Otero-Santos, J., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Pavletić, L., Persic, M., Pihet, M., Pirola, G., Podobnik, F., Moroni, P. G. Prada, Prandini, E., Principe, G., Priyadarshi, C., Puljak, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Saturni, F. G., Schleicher, B., Schmidt, K., Schmuckermaier, F., Schubert, J. L., Schweizer, T., Sitarek, J., Sliusar, V., Sobczynska, D., Spolon, A., Stamerra, A., Strišković, J., Strom, D., Strzys, M., Suda, Y., Surić, T., Tajima, H., Takahashi, M., Takeishi, R., Tavecchio, F., Temnikov, P., Terauchi, K., Terzić, T., Teshima, M., Tosti, L., Truzzi, S., Tutone, A., Ubach, S., van Scherpenberg, J., Acosta, M. Vazquez, Ventura, S., Verguilov, V., Viale, I., Vigorito, C. F., Vitale, V., Vovk, I., Walter, R., Will, M., Wunderlich, C., Yamamoto, T., Zarić, D., Abdalla, H., Aharonian, F., Benkhali, F. Ait, Angüner, E. O., Ashkar, H., Backes, M., Baghmanyan, V., Martins, V. Barbosa, Batzofin, R., Becherini, Y., Berge, D., Bernlöhr, K., Böttcher, M., Boisson, C., Bolmont, J., de Lavergne, M. de Bony, Bradascio, F., Breuhaus, M., Brose, R., Brun, F., Bulik, T., Bylund, T., Cangemi, F., Caroff, S., Casanova, S., Cerruti, M., Chand, T., Chandra, S., Chen, A., Chibueze, O. U., Cotter, G., Cristofari, P., Mbarubucyeye, J. Damascene, Devin, J., Djannati-Ataï, A., Dmytriiev, A., Egberts, K., Ernenwein, J. -P., Fiasson, A., de Clairfontaine, G. Fichet, Fontaine, G., Füßling, M., Funk, S., Gabici, S., Ghafourizadeh, S., Giavitto, G., Glawion, D., Glicenstein, J. F., Goswami, P., Grolleron, G., Hinton, J. A., Hörbe, M., Hoischen, C., Holch, T. L., Holler, M., Horns, D., Huang, Zhiqiu, Jamrozy, M., Jankowsky, F., Joshi, V., Jung-Richardt, I., Kasai, E., Katarzyński, K., Katz, U., Khélifi, B., Kluźniak, W., Komin, Nu., Kosack, K., Kostunin, D., Lang, R. G., Stum, S. Le, Lemière, A., Lemoine-Goumard, M., Lenain, J. -P., Leuschner, F., Lohse, T., Luashvili, A., Lypova, I., Mackey, J., Majumdar, J., Malyshev, D., Marandon, V., Marchegiani, P., Martí-Devesa, G., Marx, R., Maurin, G., Meyer, M., Mitchell, A., Moderski, R., Mohrmann, L., Montanari, A., Moulin, E., Muller, J., Murach, T., Nakashima, K., de Naurois, M., Nayerhoda, A., Niemiec, J., Noel, A. Priyana, O'Brien, P., Ohm, S., Olivera-Nieto, L., Wilhelmi, E. de Ona, Ostrowski, M., Panny, S., Panter, M., Parsons, R. D., Poireau, V., Prokhorov, D. A., Prokoph, H., Pühlhofer, G., Punch, M., Quirrenbach, A., Reichherzer, P., Reimer, A., Reimer, O., Renaud, M., Rieger, F., Rowell, G., Rudak, B., Ricarte, H. Rueda, Ruiz-Velasco, E., Sahakian, V., Salzmann, H., Santangelo, A., Sasaki, M., Schäfer, J., Schüssler, F., Schutte, H. M., Schwanke, U., Shapopi, J. N. S., Sol, H., Specovius, A., Spencer, S., Stawarz, Ł., Steenkamp, R., Steinmassl, S., Steppa, C., Sushch, I., Suzuki, H., Takahashi, T., Tanaka, T., Thorpe-Morgan, C., Tluczykont, M., Tomankova, L., Tsuji, N., Uchiyama, Y., van Eldik, C., van Soelen, B., Vecchi, M., Veh, J., Venter, C., Vink, J., Wagner, S. J., White, R., Wierzcholska, A., Wong, Yu Wun, Yusafzai, A., Zacharias, M., Zanin, R., Zargaryan, D., Zdziarski, A. A., Zech, A., Zhu, S. J., Zouari, S., Żywucka, N., Acharyya, A., Adams, C. B., Batista, P., Benbow, W., Capasso, M., Christiansen, J. L., Chromey, A. J., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Foote, G. M, Fortson, L., Furniss, A., Gent, A., Hanlon, W. F, Hervet, O., Holder, J., Hona, B., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kherlakian, M., Kleiner, T. K., Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E., Millis, J., Moriarty, P., Mukherjee, R., O'Brien, S., Ong, R. A., Park, N., Patel, S. R., Pfrang, K., Pohl, M., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Ryan, J. L., Sadeh, I., Saha, L., Santander, M., Sembroski, G. H., Shang, R., Splettstoesser, M., Tak, D., Tucci, J. V., Weinstein, A., Williams, D. A., Williamson, T. J., Bosch-Ramon, V., Celma, C., Linares, M., Russell, D. M., and Sala, G.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

MAXI J1820+070 is a low-mass X-ray binary with a black hole as a compact object. This binary underwent an exceptionally bright X-ray outburst from March to October 2018, showing evidence of a non-thermal particle population through its radio emission during this whole period. The combined results of 59.5 hours of observations of the MAXI J1820+070 outburst with the H.E.S.S., MAGIC and VERITAS experiments at energies above 200 GeV are presented, together with Fermi-LAT data between 0.1 and 500 GeV, and multiwavelength observations from radio to X-rays. Gamma-ray emission is not detected from MAXI J1820+070, but the obtained upper limits and the multiwavelength data allow us to put meaningful constraints on the source properties under reasonable assumptions regarding the non-thermal particle population and the jet synchrotron spectrum. In particular, it is possible to show that, if a high-energy gamma-ray emitting region is present during the hard state of the source, its predicted flux should be at most a factor of 20 below the obtained Fermi-LAT upper limits, and closer to them for magnetic fields significantly below equipartition. During the state transitions, under the plausible assumption that electrons are accelerated up to ~ 500 GeV, the multiwavelength data and the gamma-ray upper limits lead consistently to the conclusion that a potential high-energy and very-high-energy gamma-ray emitting region should be located at a distance from the black hole ranging between 10^11 and 10^13 cm. Similar outbursts from low-mass X-ray binaries might be detectable in the near future with upcoming instruments such as CTA., Comment: 15 pages, 5 figures. Accepted for publication in MNRAS

Published
2022
Full Text
View/download PDF

12. The throughput calibration of the VERITAS telescopes

Author

Adams, C. B., Benbow, W., Brill, A., Buckley, J. H., Christiansen, J. L., Falcone, A., Feng, Q., Finley, J. P., Foote, G. M, Fortson, L., Furniss, A., Giuri, C., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hona, B., Humensky, T. B., Jin, W., Kaaret, P., Kleiner, T. K, Kumar, S., Lang, M. J., Lundy, M., Maier, G., Moriarty, P., Mukherjee, R., Rosillo, M. Nievas, O'Brien, S., Park, N., Patel, S., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Ryan, J. L., Santander, M., Weinstein, A., Williams, D. A., and Williamson, T. J

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

Context. The response of imaging atmospheric Cherenkov telescopes to incident {\gamma}-ray-initiated showers in the atmosphere changes as the telescopes age due to exposure to light and weather. These aging processes affect the reconstructed energies of the events and {\gamma}-ray fluxes. Aims. This work discusses the implementation of signal calibration methods for the Very Energetic Radiation Imaging Telescope Array System (VERITAS) to account for changes in the optical throughput and detector performance over time. Methods. The total throughput of a Cherenkov telescope is the product of camera-dependent factors, such as the photomultiplier tube gains and their quantum efficiencies, and the mirror reflectivity and Winston cone response to incoming radiation. This document summarizes different methods to determine how the camera gains and mirror reflectivity have evolved over time and how we can calibrate this changing throughput in reconstruction pipelines for imaging atmospheric Cherenkov telescopes. The implementation is validated against seven years of observations with the VERITAS telescopes of the Crab Nebula, which is a reference object in very-high-energy astronomy. Results. Regular optical throughput monitoring and the corresponding signal calibrations are found to be critical for the reconstruction of extensive air shower images. The proposed implementation is applied as a correction to the signals of the photomultiplier tubes in the telescope simulation to produce fine-tuned instrument response functions. This method is shown to be effective for calibrating the acquired {\gamma}-ray data and for recovering the correct energy of the events and photon fluxes. At the same time, it keeps the computational effort of generating Monte Carlo simulations for instrument response functions affordably low., Comment: 19 pages, 20 figures, 2 tables Received: 22 September 2021 / Accepted: 03 November 2021

Published
2021
Full Text
View/download PDF

13. Variability and Spectral Characteristics of Three Flaring Gamma-ray Quasars Observed by VERITAS and Fermi-LAT

Author

Adams, C. B., Batshoun, J., Benbow, W., Brill, A., Buckley, J. H., Capasso, M., Cavins, B., Christiansen, J. L., Coppi, P., Errando, M., Farrell, K. A, Feng, Q., Finley, J. P., Foote, G. M., Fortson, L., Furniss, A., Gent, A., Giuri, C., Hanna, D., Hassan, T., Hervet, O., Holder, J., Houck, M., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kieda, D., Krennrich, F., Kumar, S., Lundy, M., Maier, G., McGrath, C. E, Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Oppenheimer, A., Otte, A. N., Patel, S., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Rhatigan, A., Ribeiro, D., Roache, E., Ryan, J. L., Santander, M., Sembroski, G. H., Williams, D. A., Williamson, T. J, Valverde, J., Horan, D., Buson, S., Cheung, C. C., Ciprini, S., Gasparrini, D., Ojha, R., van Zyl, P., and Sironi, L.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

Flat spectrum radio quasars (FSRQs) are the most luminous blazars at GeV energies, but only rarely emit detectable fluxes of TeV gamma rays, typically during bright GeV flares. We explore the gamma-ray variability and spectral characteristics of three FSRQs that have been observed at GeV and TeV energies by Fermi-LAT and VERITAS, making use of almost 100 hours of VERITAS observations spread over 10 years: 3C 279, PKS 1222+216, and Ton 599. We explain the GeV flux distributions of the sources in terms of a model derived from a stochastic differential equation describing fluctuations in the magnetic field in the accretion disk, and estimate the timescales of magnetic flux accumulation and stochastic instabilities in their accretion disks. We identify distinct flares using a procedure based on Bayesian blocks and analyze their daily and sub-daily variability and gamma-ray energy spectra. Using observations from VERITAS as well as Fermi, Swift, and the Steward Observatory, we model the broadband spectral energy distributions of PKS 1222+216 and Ton 599 during VHE-detected flares in 2014 and 2017, respectively, strongly constraining the jet Doppler factors and gamma-ray emission region locations during these events. Finally, we place theoretical constraints on the potential production of PeV-scale neutrinos during these VHE flares., Comment: 34 pages, 13 figures. Accepted for publication in the Astrophysical Journal

Published
2021
Full Text
View/download PDF

14. Multi-Wavelength Observation Campaign of the TeV Gamma-Ray Binary HESS J0632+057 with NuSTAR, VERITAS, MDM, and Swift

Author

Tokayer, Y. M., An, H., Halpern, J. P., Kim, J., Mori, K., Hailey, C. J., Adams, C. B., Benbow, W., Brill, A., Buckley, J. H., Capasso, M., Errando, M., Falcone, A., Farrell, K. A, Foote, G. M, Fortson, L., Furniss, A., Gent, A., Giuri, C., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hona, B., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kieda, D., Lang, M. J., Maier, G., McGrath, C. E, Moriarty, P., Mukherjee, R., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Patel, S., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Ryan, J. L., Santander, M., Schlenstedt, S., Sembroski, G. H., Weinstein, A., Williams, D. A., and Williamson, T. J

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

HESS J0632+057 belongs to a rare subclass of binary systems which emits gamma-rays above 100 GeV. It stands out for its distinctive high-energy light curve, which features a sharp ``primary'' peak and broader ``secondary'' peak. We present the results of contemporaneous observations by NuSTAR and VERITAS during the secondary peak between Dec. 2019 and Feb. 2020, when the orbital phase ($\phi$) is between 0.55 and 0.75. NuSTAR detected X-ray spectral evolution, while VERITAS detected TeV emission. We fit a leptonic wind-collision model to the multi-wavelength spectra data obtained over the four NuSTAR and VERITAS observations, constraining the pulsar spin-down luminosity and the magnetization parameter at the shock. Despite long-term monitoring of the source from Oct. 2019 to Mar. 2020, the MDM observatory did not detect significant variation in H$\alpha$ and H$\beta$ line equivalent widths, an expected signature of Be-disk interaction with the pulsar. Furthermore, fitting folded Swift-XRT light curve data with an intra-binary shock model constrained the orbital parameters, suggesting two orbital phases (at $\phi_D = 0.13$ and 0.37) where the pulsar crosses the Be-disk, as well as phases for the periastron ($\phi_0 = 0.30$) and inferior conjunction ($\phi_{\text{IFC}} = 0.75$). The broad-band X-ray spectra with Swift-XRT and NuSTAR allowed us to measure a higher neutral hydrogen column density at one of the predicted disk-passing phases., Comment: 21 pages, 9 figures, accepted to ApJ

Published
2021
Full Text
View/download PDF

15. Observation of the gamma-ray binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS telescopes

Author

Adams, C. B., Benbow, W., Brill, A., Buckley, J. H., Capasso, M., Chromey, A. J., Errando, M., Falcone, A., Farrell, K. A., Feng, Q., Finley, J P., Foote, G., Fortson, L., Furniss, A., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hona, B., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kieda, D., Kleiner, T. K., Krennrich, F., Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E., Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Patel, S., Pfrang, K., Pichel, A., Pohl, M., Prado, R. R., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Rovero, A. C., Ryan, J. L., Santander, M., Schlenstedt, S., Sembroski, G. H., Shang, R., Tak, D., Vassiliev, V. V., Weinstein, A., Williams, D. A., Williamson, T. J., Acciari, V. A., Ansoldi, S., Antonelli, L. A., Engels, A. Arbet, Artero, M., Asano, K., Baack, D., Babić, A., Baquero, A., de Almeida, U. Barres, Barrio, J. A., Batković, I., González, J. Becerra, Bednarek, W., Bellizzi, L., Bernardini, E., Bernardos, M., Berti, A., Besenrieder, J., Bhattacharyya, W., Bigongiari, C., Biland, A., Blanch, O., Bökenkamp, H., Bonnol, G., Bošnjak, Ž., Busetto, G., Carosi, R., Ceribella, G., Cerruti, M., Chai, Y., Chilingarian, A., Cikota, S., Colak, S. M., Colombo, E., Contreras, J. L., Cortina, J., Covino, S., D'Amico, G., D'Elia, V., Da Vela, P., Dazzi, F., De Angelis, A., De Lotto, B., Delfino, M., Delgado, J., Mendez, C. Delgado, Depaoli, D., Di Pierro, F., Di Venere, L., Espiñeira, E. Do Souto, Prester, D. Dominis, Donini, A., Dorner, D., Doro, M., Elsaesser, D., Ramazani, V. Fallah, Fattorini, A., Fonseca, M. V., Font, L., Fruck, C., Fukami, S., Fukazawa, Y., López, R. J. García, Garczarczyk, M., Gasparyan, S., Gaug, M., Giglietto, N., Giordano, F., Gliwny, P., Godinović, N., Green, J. G., Green, D., Hadasch, D., Hahn, A., Heckmann, L., Herrera, J., Hoang, J., Hrupec, D., Hütten, M., Inada, T., Ishio, K., Iwamura, Y., Martínez, I. Jiménez, Jormanainen, J., Jouvin, L., Karjalainen, M., Kerszberg, D., Kobayashi, Y., Kubo, H., Kushida, J., Lamastra, A., Lelas, D., Leone, F., Lindfors, E., Linhoff, L., Lombardi, S., Longo, F., López-Coto, R., López-Moya, M., López-Oramas, A., Loporchio, S., 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., Mazin, D., Menchiari, S., Mender, S., Mićanović, S., Miceli, D., Miener, T., Miranda, J. M., Mirzoyan, R., Molina, E., Moralejo, A., Morcuende, D., Moreno, V., Moretti, E., Nakamori, T., Nava, L., Neustroev, V., Nigro, C., Nilsson, K., Nishijima, K., Nozaki, K. Noda S., Ohtani, Y., Oka, T., Otero-Santos, J., Paiano, S., Palatiello, M., Paneque, D., Paoletti, R., Paredes, J. M., Pavletić, L., Peñil, P., Persic, M., Pihet, M., Moroni, P. G. Prada, Prandini, E., Priyadarshi, C., Puljak, I., Rhode, W., Ribó, M., Rico, J., Righi, C., Rugliancich, A., Saha, L., Sahakyan, N., Saito, T., Sakurai, S., Satalecka, K., Saturni, F. G., Schleicher, B., Schmidt, K., Schweizer, T., Sitarek, J., Šnidarić, I., Spolon, D. Sobczynska A., Stamerra, A., Strišković, J., Strom, D., Strzys, M., Suda, Y., Surić, T., Takahashi, M., Takeishi, R., Tavecchio, F., Temnikov, P., Terzić, T., Teshima, M., Tosti, L., Truzzi, S., Tutone, A., Ubach, S., van Scherpenberg, J., Vanzo, G., Acosta, M. Vazquez, Ventura, S., Verguilov, V., Vigorito, C. F., Vitale, V., Vovk, I., Will, M., Wunderlich, C., Yamamoto, T., Zarić, D., Abdalla, H., Aharonian, F., Ait-Benkhali, F., Anguener, O., Arcaro, C., Ashkar, H., Backes, M., Martins, V. Barbosa, Barnard, M., Batzofin, R., Becherini, Y., Berge, D., Bernloehr, K., Bi, B., Boettcher, M., Boisson, C., Bolmont, J., de Bony, M., Breuhaus, M., Brose, R., Brun, F., Bulik, T., Caroff, S., Casanova, S., Chand, T., Chen, A., Cotter, G., Mbarubucyeye, J. Damascene, Devin, J., Djannati-Atai, A., Egberts, K., Ernenwein, J., Fegan, S., Fiasson, A., de Clairfontaine, G. Fichet, Fontaine, G., Fuessling, M., Funk, S., Gabici, S., Giavitto, G., Glawion, D., Glicenstein, J., Grondin, M., Hinton, J., Hofmann, W., Holch, T., Holler, M., Horns, D., Huang, Z., Jamrozy, M., Jankowsky, F., Joshi, V., Jung-Richardt, I., Kasai, E., Katarzynski, K., Khelifi, B., Komin, N., Kosack, K., Kostunin, D., Stum, S. Le, Lemiere, A., Lenain, J., Leuschner, F., Levy, C., Lohse, T., Luashvili, A., Lypova, I., Mackey, J., Majumdar, J., Malyshev, D., Marandon, V., Marchegiani, P., Marcowith, A., Marti'i-Devesa, G., Marx, R., Maurin, G., Meintjes, P., Mitchell, A., Moderski, R., Mohrmann, L., Montanari, A., Moulin, E., Muller, J., Murach, T., de Naurois, M., Nayerhoda, A., Niemiec, J., Noel, A., O'Brien, P., Ohm, S., Olivera-Nieto, L., de Ona-Wilhelmi, E., Ostrowski, M., Panny, S., Panter, M., Parsons, D., Peron, G., Poireau, V., Prokhorov, D., Prokoph, H., Puehlhofer, G., Punch, M., Quirrenbach, A., Reichherzer, P., Reimer, A., Reimer, O., Renaud, M., Rieger, F., Romoli, C., Rowell, G., Rudak, B., Ricarte, H. Rueda, Velasco, E. Ruiz, Sahakian, V., Sailer, S., Salzmann, H., Sanchez, D., Santangelo, A., Sasaki, M., Schuessler, F., Schutte, H., Schwanke, U., Senniappan, M., Shapopi, J., Simoni, R., Sol, H., Specovius, A., Spencer, S., Steenkamp, R., Steinmassl, S., Sun, L., Takahashi, T., Tanaka, T., Terrier, R., Tsuji, N., Uchiyama, Y., van Eldik, C., van Soelen, B., Veh, J., Venter, C., Vink, J., Wagner, S., White, R., Wierzcholska, A., Wong, Y. W., Zacharias, M., Zargaryan, D., Zdziarski, A., Zech, A., Zhu, S., Zouari, S., Zywucka, N., Moritani, Y., and Torres, D. F.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The results of gamma-ray observations of the binary system HESS J0632+057 collected during 450 hours over 15 years, between 2004 and 2019, are presented. Data taken with the atmospheric Cherenkov telescopes H.E.S.S., MAGIC, and VERITAS at energies above 350 GeV were used together with observations at X-ray energies obtained with Swift-XRT, Chandra, XMM-Newton, NuSTAR, and Suzaku. Some of these observations were accompanied by measurements of the H{\alpha} emission line. A significant detection of the modulation of the VHE gamma-ray fluxes with a period of 316.7+-4.4 days is reported, consistent with the period of 317.3+-0.7 days obtained with a refined analysis of X-ray data. The analysis of data of four orbital cycles with dense observational coverage reveals short timescale variability, with flux-decay timescales of less than 20 days at very high energies. Flux variations observed over the time scale of several years indicate orbit-to-orbit variability. The analysis confirms the previously reported correlation of X-ray and gamma-ray emission from the system at very high significance, but can not find any correlation of optical H{\alpha} parameters with X-ray or gamma-ray energy fluxes in simultaneous observations. The key finding is that the emission of HESS J0632+057 in the X-ray and gamma-ray energy bands is highly variable on different time scales. The ratio of gamma-ray to X-ray flux shows the equality or even dominance of the gamma-ray energy range. This wealth of new data is interpreted taking into account the insufficient knowledge of the ephemeris of the system, and discussed in the context of results reported on other gamma-ray binary systems., Comment: Accepted for publication by The Astrophysical Journal

Published
2021
Full Text
View/download PDF

16. VERITAS contributions to the 37th International Cosmic Ray Conference

Author

Adams, C. B., Archer, A., Benbow, W., Brill, A., Buckley, J. H., Capasso, M., Christiansen, J. L., Chromey, A. J., Errando, M., Falcone, A., Farrell, K. A., Feng, Q., Foote, G. M., Fortson, L., Furniss, A., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hanna, D., Hervet, O., Holder, J., Hona, B., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kleiner, T. K., Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E, Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Patel, S. R., Patel, S., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Ryan, J. L., Sadeh, I., Santander, M., Sembroski, G. H., Shang, R., Tak, D., Vassiliev, V. V., Weinstein, A., Williams, D. A., and Williamson, T. J.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

Compilation of papers presented by the VERITAS Collaboration at the 37th International Cosmic Ray Conference (ICRC), held July 12 through July 23, 2021 (online) in Berlin, Germany., Comment: html page. 2021 ICRC, Berlin, Germany

Published
2021

17. An Archival Search for Neutron-Star Mergers in Gravitational Waves and Very-High-Energy Gamma Rays

Author

Adams, C. B., Benbow, W., Brill, A., Buckley, J. H., Capasso, M., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Errando, M., Falcone, A., Farrell, K. A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gent, A., Giuri, C., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Jin, W., Kaaret, P., Kertzman, M., Kieda, D., Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E, Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Patel, S., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Ryan, J. L., Santander, M., Sembroski, G. H., Shang, R., Weinstein, A., Williams, D. A., Williamson, T. J., Bartos, I., Corley, K. R., Márka, S., Márka, Z., and Veske, D.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The recent discovery of electromagnetic signals in coincidence with neutron-star mergers has solidified the importance of multimessenger campaigns in studying the most energetic astrophysical events. Pioneering multimessenger observatories, such as LIGO/Virgo and IceCube, record many candidate signals below the detection significance threshold. These sub-threshold event candidates are promising targets for multimessenger studies, as the information provided by them may, when combined with contemporaneous gamma-ray observations, lead to significant detections. Here we describe a new method that uses such candidates to search for transient events using archival very-high-energy gamma-ray data from imaging atmospheric Cherenkov telescopes (IACTs). We demonstrate the application of this method to sub-threshold binary neutron star (BNS) merger candidates identified in Advanced LIGO's first observing run. We identify eight hours of archival VERITAS observations coincident with seven BNS merger candidates and search them for TeV emission. No gamma-ray emission is detected; we calculate upper limits on the integral flux and compare them to a short gamma-ray burst model. We anticipate this search method to serve as a starting point for IACT searches with future LIGO/Virgo data releases as well as in other sub-threshold studies for multimessenger transients, such as IceCube neutrinos. Furthermore, it can be deployed immediately with other current-generation IACTs, and has the potential for real-time use that places minimal burden on experimental operations. Lastly, this method may serve as a pilot for studies with the Cherenkov Telescope Array, which has the potential to observe even larger fields of view in its divergent pointing mode.

Published
2021
Full Text
View/download PDF

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

Author

Adams, C. B., Benbow, W., Brill, A., Brose, R., Buchovecky, M., Capasso, M., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Errando, M., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gent, A., Gillanders, G. H., Giuri, C., Hanna, D., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Jin, W., Kaaret, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krennrich, F., Kumar, S., Lang, M. J., Lundy, M., Maier, G., Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Richards, G. T., Roache, E., Ryan, J. L., Santander, M., Schlenstedt, S., Sembroski, G. H., Shang, R., Stevenson, B., Wakely, S. P., Weinstein, A., and Williams, D. A.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The Galactic Center (GC) region hosts a variety of powerful astronomical sources and rare astrophysical processes that emit a large flux of non-thermal radiation. The inner 375 pc x 600 pc region, called the Central Molecular Zone, is home to the supermassive black hole Sagittarius A*, massive cloud complexes, and particle accelerators such as supernova remnants. We present the results of our improved analysis of the very-high-energy (VHE) gamma-ray emission above 2 TeV from the GC using 125 hours of data taken with the VERITAS imaging-atmospheric Cherenkov telescope between 2010 and 2018. The central source VER J1745-290, consistent with the position of Sagittarius A*, is detected at a significance of 38 standard deviations above the background level $(38\sigma)$, and we report its spectrum and light curve. Its differential spectrum is consistent with a power law with exponential cutoff, with a spectral index of $2.12^{+0.22}_{-0.17}$, a flux normalization at 5.3 TeV of $1.27^{+0.22}_{-0.23}\times 10^{-13}$ TeV-1 cm-2 s-1, and cutoff energy of $10.0^{+4.0}_{-2.0}$ TeV. We also present results on the diffuse emission near the GC, obtained by combining data from multiple regions along the GC ridge which yield a cumulative significance of $9.5\sigma$. The diffuse GC ridge spectrum is best fit by a power law with a hard index of 2.19 $\pm$ 0.20, showing no evidence of a cutoff up to 40 TeV. This strengthens the evidence for a potential accelerator of PeV cosmic rays being present in the GC. We also provide spectra of the other sources in our field of view with significant detections, composite supernova remnant G0.9+0.1 and HESS J1746-285., Comment: 19 pages, 8 figures, Accepted for publication in Astrophysical Journal

Published
2021
Full Text
View/download PDF

19. Demonstration of stellar intensity interferometry with the four VERITAS telescopes

Author

Abeysekara, A. U., Benbow, W., Brill, A., Buckley, J. H., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Davis, J., Falcone, A., Feng, Q., 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., Kaaret, P., Kertzman, M., Kieda, D., Krennrich, F., Kumar, S., LeBohec, T., Lin, T. T. Y., Lundy, M., Maier, G., Matthews, N., Moriarty, P., Nievas-Rosillo, R. Mukherjee M., O'Brien, S., Ong, R. A., Otte, A. N., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Richards, G. T., Roache, E., Ryan, J. L., Santander, M., Sembroski, G. H., Wakely, S. P., Weinstein, A., Wilcox, P., Williams, D. A., and Williamson, T. J

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract

High angular resolution observations at optical wavelengths provide valuable insights in stellar astrophysics, directly measuring fundamental stellar parameters, and probing stellar atmospheres, circumstellar disks, elongation of rapidly rotating stars, and pulsations of Cepheid variable stars. The angular size of most stars are of order one milli-arcsecond or less, and to spatially resolve stellar disks and features at this scale requires an optical interferometer using an array of telescopes with baselines on the order of hundreds of meters. We report on the successful implementation of a stellar intensity interferometry system developed for the four VERITAS imaging atmospheric-Cherenkov telescopes. The system was used to measure the angular diameter of the two sub-mas stars $\beta$ Canis Majoris and $\epsilon$ Orionis with a precision better than 5%. The system utilizes an off-line approach where starlight intensity fluctuations recorded at each telescope are correlated post-observation. The technique can be readily scaled onto tens to hundreds of telescopes, providing a capability that has proven technically challenging to current generation optical amplitude interferometry observatories. This work demonstrates the feasibility of performing astrophysical measurements with imaging atmospheric-Cherenkov telescope arrays as intensity interferometers and the promise for integrating an intensity interferometry system within future observatories such as the Cherenkov Telescope Array., Comment: Accepted for publication in Nature Astronomy (2020)

Published
2020
Full Text
View/download PDF

20. VERITAS Discovery of VHE Emission from the Radio Galaxy 3C 264: A Multi-Wavelength Study

Author

Archer, A., Benbow, W., Bird, R., Brill, A., Buchovecky, M., Buckley, J. H., Carini, M. T., Christiansen, J. L., Chromey, A. J., Daniel, M. K., Errando, M., Falcone, A., Feng, Q., Fortin, P., Fortson, L., Furniss, A., Gent, A., Georganopoulos, M., Gillanders, G. H., Giuri, C., Gueta, O., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Kaaret, P., Kertzman, M., Kieda, D., Krennrich, F., Lang, M. J., Lin, T. T. Y., Lister, M. L., Lundy, M., Maier, G., Meyer, E. T., Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Ramirez, K., Reynolds, P. T., Ribeiro, D., Richards, G. T., Roache, E., Rulten, C., Ryan, J. L., Sadun, A., Santander, M., Scott, S. S., Sembroski, G. H., Shahinyan, K., Shang, R., Stevenson, B., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Wilcox, P., Wilhelm, A., Williams, D. A., and Williamson, T. J

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The radio source 3C 264, hosted by the giant elliptical galaxy NGC 3862, was observed with VERITAS between February 2017 and May 2019. These deep observations resulted in the discovery of very-high-energy (VHE; E $>100$ GeV) $\gamma$-ray emission from this active galaxy. An analysis of $\sim$57 hours of quality-selected live time yields a detection at the position of the source, corresponding to a statistical significance of 7.8 standard deviations above background. The observed VHE flux is variable on monthly time scales, with an elevated flux seen in 2018 observations. The VHE emission during this elevated state is well-characterized by a power-law spectrum with a photon index $\Gamma = 2.20 \pm 0.27$ and flux F($>315$ GeV) = ($7.6\pm 1.2_{\mathrm stat} \pm 2.3_{\mathrm syst})\times 10^{-13}$ cm$^{-2}$ s$^{-1}$, or approximately 0.7% of the Crab Nebula flux above the same threshold. 3C 264 ($z = 0.0217$) is the most distant radio galaxy detected at VHE, and the elevated state is thought to be similar to that of the famously outbursting jet in M 87. Consequently, extensive contemporaneous multi-wavelength data were acquired in 2018 at the time of the VHE high state. An analysis of these data, including VLBA, VLA, HST, Chandra and Swift observations in addition to the VERITAS data, is presented, along with a discussion of the resulting spectral energy distribution., Comment: 19 pages, 11 figures, Accepted for publication in Astrophysical Journal

Published
2020
Full Text
View/download PDF

21. 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

22. A decade of multi-wavelength observations of the TeV blazar 1ES 1215+303: Extreme shift of the synchrotron peak frequency and long-term optical-gamma-ray flux increase

Author

Valverde, Janeth, Horan, Deirdre, Bernard, Denis, Fegan, Stephen, Abeysekara, A. U., Archer, A., Benbow, W., Bird, R., Brill, A., Brose, R., Buchovecky, M., Buckley, J. H., Christiansen, J. L., Cui, W., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Kaaret, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Lang, M. J., Maier, G., Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pfrang, K., Pichel, A., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Richards, G. T., Roache, E., Sadeh, I., Santander, M., Scott, S. S., Sembroski, G. H., Shahinyan, K., Shang, R., Sushch, I., Vassiliev, V. V., Weinstein, A., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., Williamson, T. J, Noto, Giuliana, Edwards, P. G., Piner, B. G., Ramazani, V. Fallah, Hovatta, T., Jormanainen, J., Lindfors, E., Nilsson, K., Takalo, L., Kovalev, Y. Y., Lister, M. L., Pushkarev, A. B., Savolainen, T., Kiehlmann, S., Max-Moerbeck, W., Readhead, A. C. S., Lähteenmäki, A., and Tornikoski, M.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

Blazars are known for their variability on a wide range of timescales at all wavelengths. Most studies of TeV gamma-ray blazars focus on short timescales, especially during flares. With a decade of observations from the Fermi-LAT and VERITAS, we present an extensive study of the long-term multi-wavelength radio-to-gamma-ray flux-density variability, with the addition of a couple of short-time radio-structure and optical polarization observations of the blazar 1ES 1215+303 (z=0.130), with a focus on its gamma-ray emission from 100 MeV to 30 TeV. Multiple strong GeV gamma-ray flares, a long-term increase in the gamma-ray and optical flux baseline and a linear correlation between these two bands are observed over the ten-year period. Typical HBL behaviors are identified in the radio morphology and broadband spectrum of the source. Three stationary features in the innermost jet are resolved by VLBA at 43.1, 22.2, and 15.3 GHz. We employ a two-component synchrotron self-Compton model to describe different flux states of the source, including the epoch during which an extreme shift in energy of the synchrotron peak frequency from infrared to soft X-rays is observed., Comment: Accepted for publication in the Astrophysical Journal

Published
2020
Full Text
View/download PDF

23. 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

24. VERITAS Detection of LS 5039 and HESS J1825-137

Author

VERITAS Collaboration, Abeysekara, A. U., Benbow, W., Bird, R., Brose, R., Christiansen, J. L., Chromey, A. J., Cui, W., Daniel, M. K., Falcone, A., Fortson, L., 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., Lang, M. J., Maier, G., Moriarty, P., Nieto, D., Nievas-Rosillo, M., Ong, R. A., Pandel, D., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Richards, G. T., Roache, E., Sadeh, I., Santander, M., Sembroski, G. H., Weinstein, A., Wilcox, P., Williams, D. A., and Williamson, T. J

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

With 8 hours of observations, VERITAS confirms the detection of two very high energy gamma-ray sources. The gamma-ray binary LS 5039 is detected with a statistical significance of $8.8\sigma$. The measured flux above 1 TeV is $(2.5 \pm 0.4) \times 10^{-12} \rm \, cm^{-2} \, s^{-1}$ near inferior conjunction and $(7.8 \pm 2.8) \times 10^{-13} \rm \, cm^{-2} \, s^{-1}$ near superior conjunction. The pulsar wind nebula HESS J1825-137 is detected with a statistical significance of $6.7\sigma$ and a measured flux above 1 TeV of $(3.9 \pm 0.8) \times 10^{-12} \rm \, cm^{-2} \, s^{-1}$., Comment: 4 pages, 2 figures

Published
2020
Full Text
View/download PDF

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

Author

Archer, A., Benbow, W., Bird, R., Brill, A., Brose, R., Buchovecky, M., Christiansen, J. L., Chromey, A. J., Cui, W., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Kaaret, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Lang, M. J., Maier, G., Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Richards, G. T., Roache, E., Sadeh, I., Santander, M., Schlenstedt, S., Sembroski, G. H., Sushch, I., Weinstein, A., Wilcox, P., Wilhelm, A., Williams, D. A., Williamson, T. J, Hailey, C. J., Mandel, S., and Mori, K.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

HESS J0632+057 is a gamma-ray binary composed of a compact object orbiting a Be star with a period of about $315$ days. Extensive X-ray and TeV gamma-ray observations have revealed a peculiar light curve containing two peaks, separated by a dip. We present the results of simultaneous observations in hard X-rays with NuSTAR and in TeV gamma-rays with VERITAS, performed in November and December 2017. These observations correspond to the orbital phases $\phi\approx0.22$ and $0.3$, where the fluxes are rising towards the first light-curve peak. A significant variation of the spectral index from 1.77$\pm$0.05 to 1.56$\pm$0.05 is observed in the X-ray data. The multi-wavelength spectral energy distributions (SED) derived from the observations are interpreted in terms of a leptonic model, in which the compact object is assumed to be a pulsar and non-thermal radiation is emitted by high-energy electrons accelerated at the shock formed by the collision between the stellar and pulsar wind. The results of the SED fitting show that our data can be consistently described within this scenario, and allow us to estimate the magnetization of the pulsar wind at the location of the shock formation. The constraints on the pulsar-wind magnetization provided by our results are shown to be consistent with those obtained from other systems., Comment: Accepted for publication in The Astrophysical Journal

Published
2019
Full Text
View/download PDF

26. 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

27. VERITAS contributions to the 36th International Cosmic Ray Conference

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., Das, S., Falcone, A., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gent, A., Gillanders, G. H., Giuri, C., Gueta, O., Hanna, D., Hassan, T., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Kaaret, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Kumar, S., Lang, M. J., Lin, T. T. Y., Lundy, M., Maier, G., Matthews, N., Moriarty, P., Mukherjee, R., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., Pfrang, K., Pohl, M., Prado, R. R., Pueschel, E., Quinn, J., Ragan, K., Reynolds, P. T., Ribeiro, D., Richards, G. T., Roache, E., Sadeh, I., Santander, M., Schlenstedt, S., Scott, S. S., Sembroski, G. H., Shang, R., Vassiliev, V. V., Wakely, S. P., Weinstein, A., Wells, R. M., Wilcox, P., Williams, D. A., and Williamson, T. J

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

Compilation of papers presented by the VERITAS Collaboration at the 36th International Cosmic Ray Conference (ICRC), held July 24 through August 1, 2019 in Madison, Wisconsin., Comment: html page. 2019 ICRC, Madison, Wisconsin

Published
2019

28. 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

29. Direct measurement of stellar angular diameters by the VERITAS Cherenkov Telescopes

Author

Benbow, W., Bird, R., Brill, A., Brose, R., Chromey, A. J., Daniel, M. K., Feng, Q., Finley, J. P., Fortson, L., Furniss, A., Gillanders, G. H., Giuri, C., Gueta, O., Hanna, D., Halpern, J., Hassan, T., Holder, J., Hughes, G., Humensky, T. B., Joyce, A. M., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Lang, M. J., Lin, T. T. Y., Maier, G., Matthews, N., Moriarty, P., Mukherjee, R., Nieto, D., Nievas-Rosillo, M., O'Brien, S., Ong, R. A., 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., Wakely, S. P., Wells, R. M., Wilcox, P., Wilhelm, A., Williams, D. A., and Williamson, T. J.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

The angular size of a star is a critical factor in determining its basic properties. Direct measurement of stellar angular diameters is difficult: at interstellar distances stars are generally too small to resolve by any individual imaging telescope. This fundamental limitation can be overcome by studying the diffraction pattern in the shadow cast when an asteroid occults a star, but only when the photometric uncertainty is smaller than the noise added by atmospheric scintillation. Atmospheric Cherenkov telescopes used for particle astrophysics observations have not generally been exploited for optical astronomy due to the modest optical quality of the mirror surface. However, their large mirror area makes them well suited for such high-time-resolution precision photometry measurements. Here we report two occultations of stars observed by the VERITAS Cherenkov telescopes with millisecond sampling, from which we are able to provide a direct measurement of the occulted stars' angular diameter at the $\leq0.1$ milliarcsecond scale. This is a resolution never achieved before with optical measurements and represents an order of magnitude improvement over the equivalent lunar occultation method. We compare the resulting stellar radius with empirically derived estimates from temperature and brightness measurements, confirming the latter can be biased for stars with ambiguous stellar classifications., Comment: Accepted for publication in Nature Astronomy

Published
2019
Full Text
View/download PDF

30. Solar Jet Hunter: a citizen science initiative to identify and characterize coronal jets at 304 AA

Author

Musset, S., primary, Jol, P., additional, Sankar, R., additional, Alnahari, S., additional, Kapsiak, C., additional, Ostlund, E., additional, Lasko, K., additional, Glesener, L., additional, Fortson, L., additional, Fleishman, G.D., additional, Navdeep Panesar, K., additional, Zhang, Y., additional, Jeunon, M., additional, and Hurlburt, N., additional

Published
2024
Full Text
View/download PDF

31. 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

32. 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

33. 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

34. 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

35. 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

36. HESS J1943+213: An Extreme Blazar Shining Through The Galactic Plane

Author

The VERITAS Collaboration, Archer, A., Benbow, W., Bird, R., Brose, R., Buchovecky, M., Bugaev, V., Cui, W., Daniel, M. K., 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., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Lin, T. T. Y., 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., 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., Brisken, W. F., and Pontrelli, P.

Subjects
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

HESS J1943+213 is a very-high-energy (VHE; $>$100 GeV) $\gamma$-ray source in the direction of the Galactic Plane. Studies exploring the classification of the source are converging towards its identification as an extreme synchrotron BL Lac object. Here we present 38 hours of VERITAS observations of HESS J1943+213 taken over two years. The source is detected with $\sim$20 standard deviations significance, showing a remarkably stable flux and spectrum in VHE $\gamma$-rays. Multi-frequency very-long-baseline array (VLBA) observations of the source confirm the extended, jet-like structure previously found in the 1.6 GHz band with European VLBI Network and detect this component in the 4.6 GHz and the 7.3 GHz bands. The radio spectral indices of the core and the jet and the level of polarization derived from the VLBA observations are in a range typical for blazars. Data from VERITAS, $Fermi$-LAT, $Swift$-XRT, FLWO 48$''$ telescope, and archival infrared and hard X-ray observations are used to construct and model the spectral energy distribution (SED) of the source with a synchrotron-self-Compton model. The well-measured $\gamma$-ray peak of the SED with VERITAS and $Fermi$-LAT provides constraining upper limits on the source redshift. Possible contribution of secondary $\gamma$-rays from ultra-high-energy cosmic ray-initiated electromagnetic cascades to the $\gamma$-ray emission is explored, finding that only a segment of the VHE spectrum can be accommodated with this process. A variability search is performed across X-ray and $\gamma$-ray bands. No statistically significant flux or spectral variability is detected., Comment: Accepted for publication in The Astrophysical Journal

Published
2018
Full Text
View/download PDF

37. 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

38. 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

39. 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

40. Muon Hunter: a Zooniverse project

Author

Bird, R., Daniel, M. K., Dickinson, H., Feng, Q., Fortson, L., Furniss, A., Jarvis, J., Mukherjee, R., Ong, R., Sadeh, I., and Williams, D.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Physics - Data Analysis, Statistics and Probability
Abstract

The large datasets and often low signal-to-noise inherent to the raw data of modern astroparticle experiments calls out for increasingly sophisticated event classification techniques. Machine learning algorithms, such as neural networks, have the potential to outperform traditional analysis methods, but come with the major challenge of identifying reliably classified training samples from real data. Citizen science represents an effective approach to sort through the large datasets efficiently and meet this challenge. Muon Hunter is a project hosted on the Zooniverse platform, wherein volunteers sort through pictures of data from the VERITAS cameras to identify muon ring images. Each image is classified multiple times to produce a "clean" dataset used to train and validate a convolutional neural network model both able to reject background events and identify suitable calibration data to monitor the telescope performance as a function of time., Comment: Presented at TAUP 2017

Published
2018

41. Machine learning for the Zwicky transient facility

Author

Mahabal, A, Rebbapragada, U, Walters, R, Masci, FJ, Blagorodnova, N, van Roestel, J, Ye, QZ, Biswas, R, Burdge, K, Chang, CK, Duev, DA, Zach Golkhou, V, Miller, AA, Nordin, J, Ward, C, Adams, S, Bellm, EC, Branton, D, Bue, B, Cannella, C, Connolly, A, Dekany, R, Feindt, U, Hung, T, Fortson, L, Frederick, S, Fremling, C, Gezari, S, Graham, M, Groom, S, Kasliwal, MM, Kulkarni, S, Kupfer, T, Lin, HW, Lintott, C, Lunnan, R, Parejko, J, Prince, TA, Riddle, R, Rusholme, B, Saunders, N, Sedaghat, N, Shupe, DL, Singer, LP, Soumagnac, MT, Szkody, P, Tachibana, Y, Tirumala, K, van Velzen, S, and Wright, D

Subjects
Machine Learning, Sky Surveys, Time Domain, astro-ph.IM, Astronomical and Space Sciences, Astronomy & Astrophysics
Abstract

The Zwicky Transient Facility is a large optical survey in multiple filters producing hundreds of thousands of transient alerts per night. We describe here various machine learning (ML) implementations and plans to make the maximal use of the large data set by taking advantage of the temporal nature of the data, and further combining it with other data sets. We start with the initial steps of separating bogus candidates from real ones, separating stars and galaxies, and go on to the classification of real objects into various classes. Besides the usual methods (e.g., based on features extracted from light curves) we also describe early plans for alternate methods including the use of domain adaptation, and deep learning. In a similar fashion we describe efforts to detect fast moving asteroids. We also describe the use of the Zooniverse platform for helping with classifications through the creation of training samples, and active learning. Finally we mention the synergistic aspects of ZTF and LSST from the ML perspective.

Published
2019

42. Science with the Cherenkov Telescope Array

Author

Consortium, The Cherenkov Telescope Array, Acharya, B. S., Agudo, I., Samarai, I. Al, Alfaro, R., Alfaro, J., Alispach, C., Batista, R. Alves, Amans, J. -P., Amato, E., Ambrosi, G., Antolini, E., Antonelli, L. A., Aramo, C., Araya, M., Armstrong, T., Arqueros, F., Arrabito, L., Asano, K., Ashley, M., Backes, M., Balazs, C., Balbo, M., Ballester, O., Ballet, J., Bamba, A., Barkov, M., de Almeida, U. Barres, Barrio, J. A., Bastieri, D., Becherini, Y., Belfiore, A., Benbow, W., Berge, D., Bernardini, E., Bernardini, M. G., Bernardos, M., Bernlöhr, K., Bertucci, B., Biasuzzi, B., Bigongiari, C., Biland, A., Bissaldi, E., Biteau, J., Blanch, O., Blazek, J., Boisson, C., Bolmont, J., Bonanno, G., Bonardi, A., Bonavolontà, C., Bonnoli, G., Bosnjak, Z., Böttcher, M., Braiding, C., Bregeon, J., Brill, A., Brown, A. M., Brun, P., Brunetti, G., Buanes, T., Buckley, J., Bugaev, V., Bühler, R., Bulgarelli, A., Bulik, T., Burton, M., Burtovoi, A., Busetto, G., Canestrari, R., Capalbi, M., Capitanio, F., Caproni, A., Caraveo, P., Cárdenas, V., Carlile, C., Carosi, R., Carquín, E., Carr, J., Casanova, S., Cascone, E., Catalani, F., Catalano, O., Cauz, D., Cerruti, M., Chadwick, P., Chaty, S., Chaves, R. C. G., Chen, A., Chen, X., Chernyakova, M., Chikawa, M., Christov, A., Chudoba, J., Cieślar, M., Coco, V., Colafrancesco, S., Colin, P., Conforti, V., Connaughton, V., Conrad, J., Contreras, J. L., Cortina, J., Costa, A., Costantini, H., Cotter, G., Covino, S., Crocker, R., Cuadra, J., Cuevas, O., Cumani, P., D'Aì, A., D'Ammando, F., D'Avanzo, P., D'Urso, D., Daniel, M., Davids, I., Dawson, B., Dazzi, F., De Angelis, A., Anjos, R. de Cássia dos, De Cesare, G., De Franco, A., Pino, E. M. de Gouveia Dal, de la Calle, I., Lopez, R. de los Reyes, De Lotto, B., De Luca, A., De Lucia, M., de Naurois, M., Wilhelmi, E. de Oña, De Palma, F., De Persio, F., de Souza, V., Deil, C., Del Santo, M., Delgado, C., della Volpe, D., Di Girolamo, T., Di Pierro, F., Di Venere, L., Díaz, C., Dib, C., Diebold, S., Djannati-Ataï, A., Domínguez, A., Prester, D. Dominis, Dorner, D., Doro, M., Drass, H., Dravins, D., Dubus, G., Dwarkadas, V. V., Ebr, J., Eckner, C., Egberts, K., Einecke, S., Ekoume, T. R. N., Elsässer, D., Ernenwein, J. -P., Espinoza, C., Evoli, C., Fairbairn, M., Falceta-Goncalves, D., Falcone, A., Farnier, C., Fasola, G., Fedorova, E., Fegan, S., Fernandez-Alonso, M., Fernández-Barral, A., Ferrand, G., Fesquet, M., Filipovic, M., Fioretti, V., Fontaine, G., Fornasa, M., Fortson, L., Coromina, L. Freixas, Fruck, C., Fujita, Y., Fukazawa, Y., Funk, S., Füßling, M., Gabici, S., Gadola, A., Gallant, Y., Garcia, B., López, R. Garcia, Garczarczyk, M., Gaskins, J., Gasparetto, T., Gaug, M., Gerard, L., Giavitto, G., Giglietto, N., Giommi, P., Giordano, F., Giro, E., Giroletti, M., Giuliani, A., Glicenstein, J. -F., Gnatyk, R., Godinovic, N., Goldoni, P., Gómez-Vargas, G., González, M. M., González, J. M., Götz, D., Graham, J., Grandi, P., Granot, J., Green, A. J., Greenshaw, T., Griffiths, S., Gunji, S., Hadasch, D., Hara, S., Hardcastle, M. J., Hassan, T., Hayashi, K., Hayashida, M., Heller, M., Helo, J. C., Hermann, G., Hinton, J., Hnatyk, B., Hofmann, W., Holder, J., Horan, D., Hörandel, J., Horns, D., Horvath, P., Hovatta, T., Hrabovsky, M., Hrupec, D., Humensky, T. B., Hütten, M., Iarlori, M., Inada, T., Inome, Y., Inoue, S., Inoue, T., Inoue, Y., Iocco, F., Ioka, K., Iori, M., Ishio, K., Iwamura, Y., Jamrozy, M., Janecek, P., Jankowsky, D., Jean, P., Jung-Richardt, I., Jurysek, J., Kaaret, P., Karkar, S., Katagiri, H., Katz, U., Kawanaka, N., Kazanas, D., Khélifi, B., Kieda, D. B., Kimeswenger, S., Kimura, S., Kisaka, S., Knapp, J., Knödlseder, J., Koch, B., Kohri, K., Komin, N., Kosack, K., Kraus, M., Krause, M., Krauß, F., Kubo, H., Mezek, G. Kukec, Kuroda, H., Kushida, J., La Palombara, N., Lamanna, G., Lang, R. G., Lapington, J., Blanc, O. Le, Leach, S., Lees, J. -P., Lefaucheur, J., de Oliveira, M. A. Leigui, Lenain, J. -P., Lico, R., Limon, M., Lindfors, E., Lohse, T., Lombardi, S., Longo, F., López, M., López-Coto, R., Lu, C. -C., Lucarelli, F., Luque-Escamilla, P. L., Lyard, E., Maccarone, M. C., Maier, G., Majumdar, P., Malaguti, G., Mandat, D., Maneva, G., Manganaro, M., Mangano, S., Marcowith, A., Marín, J., Markoff, S., Martí, J., Martin, P., Martínez, M., Martínez, G., Masetti, N., Masuda, S., Maurin, G., Maxted, N., Mazin, D., Medina, C., Melandri, A., Mereghetti, S., Meyer, M., Minaya, I. A., Mirabal, N., Mirzoyan, R., Mitchell, A., Mizuno, T., Moderski, R., Mohammed, M., Mohrmann, L., Montaruli, T., Moralejo, A., Morcuende-Parrilla, D., Mori, K., Morlino, G., Morris, P., Morselli, A., Moulin, E., Mukherjee, R., Mundell, C., Murach, T., Muraishi, H., Murase, K., Nagai, A., Nagataki, S., Nagayoshi, T., Naito, T., Nakamori, T., Nakamura, Y., Niemiec, J., Nieto, D., Nikołajuk, M., Nishijima, K., Noda, K., Nosek, D., Novosyadlyj, B., Nozaki, S., O'Brien, P., Oakes, L., Ohira, Y., Ohishi, M., Ohm, S., Okazaki, N., Okumura, A., Ong, R. A., Orienti, M., Orito, R., Osborne, J. P., Ostrowski, M., Otte, N., Oya, I., Padovani, M., Paizis, A., Palatiello, M., Palatka, M., Paoletti, R., Paredes, J. M., Pareschi, G., Parsons, R. D., Pe'er, A., Pech, M., Pedaletti, G., Perri, M., Persic, M., Petrashyk, A., Petrucci, P., Petruk, O., Peyaud, B., Pfeifer, M., Piano, G., Pisarski, A., Pita, S., Pohl, M., Polo, M., Pozo, D., Prandini, E., Prast, J., Principe, G., Prokhorov, D., Prokoph, H., Prouza, M., Pühlhofer, G., Punch, M., Pürckhauer, S., Queiroz, F., Quirrenbach, A., Rainò, S., Razzaque, S., Reimer, O., Reimer, A., Reisenegger, A., Renaud, M., Rezaeian, A. H., Rhode, W., Ribeiro, D., Ribó, M., Richtler, T., Rico, J., Rieger, F., Riquelme, M., Rivoire, S., Rizi, V., Rodriguez, J., Fernandez, G. Rodriguez, Vázquez, J. J. Rodríguez, Rojas, G., Romano, P., Romeo, G., Rosado, J., Rovero, A. C., Rowell, G., Rudak, B., Rugliancich, A., Rulten, C., Sadeh, I., Safi-Harb, S., Saito, T., Sakaki, N., Sakurai, S., Salina, G., Sánchez-Conde, M., Sandaker, H., Sandoval, A., Sangiorgi, P., Sanguillon, M., Sano, H., Santander, M., Sarkar, S., Satalecka, K., Saturni, F. G., Schioppa, E. J., Schlenstedt, S., Schneider, M., Schoorlemmer, H., Schovanek, P., Schulz, A., Schussler, F., Schwanke, U., Sciacca, E., Scuderi, S., Seitenzahl, I., Semikoz, D., Sergijenko, O., Servillat, M., Shalchi, A., Shellard, R. C., Sidoli, L., Siejkowski, H., Sillanpää, A., Sironi, G., Sitarek, J., Sliusar, V., Slowikowska, A., Sol, H., Stamerra, A., Stanič, S., Starling, R., Stawarz, Ł., Stefanik, S., Stephan, M., Stolarczyk, T., Stratta, G., Straumann, U., Suomijarvi, T., Supanitsky, A. D., Tagliaferri, G., Tajima, H., Tavani, M., Tavecchio, F., Tavernet, J. -P., Tayabaly, K., Tejedor, L. A., Temnikov, P., Terada, Y., Terrier, R., Terzic, T., Teshima, M., Testa, V., Thoudam, S., Tian, W., Tibaldo, L., Tluczykont, M., Peixoto, C. J. Todero, Tokanai, F., Tomastik, J., Tonev, D., Tornikoski, M., Torres, D. F., Torresi, E., Tosti, G., Tothill, N., Tovmassian, G., Travnicek, P., Trichard, C., Trifoglio, M., Pujadas, I. Troyano, Tsujimoto, S., Umana, G., Vagelli, V., Vagnetti, F., Valentino, M., Vallania, P., Valore, L., van Eldik, C., Vandenbroucke, J., Varner, G. S., Vasileiadis, G., Vassiliev, V., Acosta, M. Vázquez, Vecchi, M., Vega, A., Vercellone, S., Veres, P., Vergani, S., Verzi, V., Vettolani, G. P., Viana, A., Vigorito, C., Villanueva, J., Voelk, H., Vollhardt, A., Vorobiov, S., Vrastil, M., Vuillaume, T., Wagner, S. J., Wagner, R., Walter, R., Ward, J. E., Warren, D., Watson, J. J., Werner, F., White, M., White, R., Wierzcholska, A., Wilcox, P., Will, M., Williams, D. A., Wischnewski, R., Wood, M., Yamamoto, T., Yamazaki, R., Yanagita, S., Yang, L., Yoshida, T., Yoshiike, S., Yoshikoshi, T., Zacharias, M., Zaharijas, G., Zampieri, L., Zandanel, F., Zanin, R., Zavrtanik, M., Zavrtanik, D., Zdziarski, A. A., Zech, A., Zechlin, H., Zhdanov, V. I., Ziegler, A., and Zorn, J.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
Abstract

The Cherenkov Telescope Array, CTA, will be the major global observatory for very high energy gamma-ray astronomy over the next decade and beyond. The scientific potential of CTA is extremely broad: from understanding the role of relativistic cosmic particles to the search for dark matter. CTA is an explorer of the extreme universe, probing environments from the immediate neighbourhood of black holes to cosmic voids on the largest scales. Covering a huge range in photon energy from 20 GeV to 300 TeV, CTA will improve on all aspects of performance with respect to current instruments. The observatory will operate arrays on sites in both hemispheres to provide full sky coverage and will hence maximize the potential for the rarest phenomena such as very nearby supernovae, gamma-ray bursts or gravitational wave transients. With 99 telescopes on the southern site and 19 telescopes on the northern site, flexible operation will be possible, with sub-arrays available for specific tasks. CTA will have important synergies with many of the new generation of major astronomical and astroparticle observatories. Multi-wavelength and multi-messenger approaches combining CTA data with those from other instruments will lead to a deeper understanding of the broad-band non-thermal properties of target sources. The CTA Observatory will be operated as an open, proposal-driven observatory, with all data available on a public archive after a pre-defined proprietary period. Scientists from institutions worldwide have combined together to form the CTA Consortium. This Consortium has prepared a proposal for a Core Programme of highly motivated observations. The programme, encompassing approximately 40% of the available observing time over the first ten years of CTA operation, is made up of individual Key Science Projects (KSPs), which are presented in this document., Comment: 213 pages, including references and glossary. Version 2: credits and references updated, some figures updated, and author list updated

Published
2017
Full Text
View/download PDF

43. 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

44. 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

45. Cherenkov Telescope Array Contributions to the 35th International Cosmic Ray Conference (ICRC2017)

Author

Acero, F., Acharya, B. S., Portella, V. Acín, Adams, C., Agudo, I., Aharonian, F., Samarai, I. Al, Alberdi, A., Alcubierre, M., Alfaro, R., Alfaro, J., Alispach, C., Aloisio, R., Batista, R. Alves, Amans, J. -P., Amato, E., Ambrogi, L., Ambrosi, G., Ambrosio, M., Anderson, J., Anduze, M., Angüner, E. O., Antolini, E., Antonelli, L. A., Antonuccio, V., Antoranz, P., Aramo, C., Araya, M., Arcaro, C., Armstrong, T., Arqueros, F., Arrabito, L., Arrieta, M., Asano, K., Asano, A., Ashley, M., Aubert, P., Singh, C. B., Babic, A., Backes, M., Bajtlik, S., Balazs, C., Balbo, M., Ballester, O., Ballet, J., Ballo, L., Balzer, A., Bamba, A., Bandiera, R., Barai, P., Barbier, C., Barcelo, M., Barkov, M., de Almeida, U. Barres, Barrio, J. A., Bastieri, D., Bauer, C., Becciani, U., Becherini, Y., Tjus, J. Becker, Bednarek, W., Belfiore, A., Benbow, W., Benito, M., Berge, D., Bernardini, E., Bernardini, M. G., Bernardos, M., Bernhard, S., Bernlöhr, K., Salucci, C. Bertinelli, Bertucci, B., Besel, M. -A., Beshley, V., Bettane, J., Bhatt, N., Bhattacharyya, W., Bhattachryya, S., Biasuzzi, B., Bicknell, G., Bigongiari, C., Biland, A., Bilinsky, A., Bird, R., Bissaldi, E., Biteau, J., Bitossi, M., Blanch, O., Blasi, P., Blazek, J., Boccato, C., Bockermann, C., Boehm, C., Bohacova, M., Boisson, C., Bolmont, J., Bonanno, G., Bonardi, A., Bonavolontà, C., Bonnoli, G., Borkowski, J., Bose, R., Bosnjak, Z., Böttcher, M., Boutonnet, C., Bouyjou, F., Bowman, L., Bozhilov, V., Braiding, C., Brau-Nogué, S., Bregeon, J., Briggs, M., Brill, A., Brisken, W., Bristow, D., Britto, R., Brocato, E., Brown, A. M., Brown, S., Brügge, K., Brun, P., Brun, F., Brunetti, L., Brunetti, G., Bruno, P., Bryan, M., Buckley, J., Bugaev, V., Bühler, R., Bulgarelli, A., Bulik, T., Burton, M., Burtovoi, A., Busetto, G., Buson, S., Buss, J., Byrum, K., Caccianiga, A., Cameron, R., Canelli, F., Canestrari, R., Capalbi, M., Capasso, M., Capitanio, F., Caproni, A., Capuzzo-Dolcetta, R., Caraveo, P., Cárdenas, V., Cardenzana, J., Cardillo, M., Carlile, C., Caroff, S., Carosi, R., Carosi, A., Carquín, E., Carr, J., Casandjian, J. -M., Casanova, S., Cascone, E., Castro-Tirado, A. J., Mora, J. Castroviejo, Catalani, F., Catalano, O., Cauz, D., Silva, C. Celestino, Celli, S., Cerruti, M., Chabanne, E., Chadwick, P., Chakraborty, N., Champion, C., Chatterjee, A., Chaty, S., Chaves, R., Chen, A., Chen, X., Cheng, K., Chernyakova, M., Chikawa, M., Chitnis, V. R., Christov, A., Chudoba, J., Cieślar, M., Clark, P., Coco, V., Colafrancesco, S., Colin, P., Colombo, E., Colome, J., Colonges, S., Conforti, V., Connaughton, V., Conrad, J., Contreras, J. L., Cornat, R., Cortina, J., Costa, A., Costantini, H., Cotter, G., Courty, B., Covino, S., Covone, G., Cristofari, P., Criswell, S. J., Crocker, R., Croston, J., Crovari, C., Cuadra, J., Cuevas, O., Cui, X., Cumani, P., Cusumano, G., D'Aì, A., D'Ammando, F., D'Avanzo, P., D'Urso, D., Da Vela, P., Dale, Ø., Dang, V. T., Dangeon, L., Daniel, M., Davids, I., Dawson, B., Dazzi, F., De Angelis, A., De Caprio, V., Anjos, R. de Cássia dos, De Cesare, G., De Franco, A., De Frondat, F., Pino, E. M. de Gouveia Dal, de la Calle, I., De Lisio, C., Lopez, R. de los Reyes, De Lotto, B., De Luca, A., De Lucia, M., Neto, J. R. T. de Mello, de Naurois, M., Wilhelmi, E. de Oña, De Palma, F., De Persio, F., de Souza, V., Decock, J., Deil, C., Deiml, P., Del Santo, M., Delagnes, E., Deleglise, G., Reznicek, M. Delfino, Delgado, C., Mengual, J. Delgado, Della Ceca, R., della Volpe, D., Detournay, M., Devin, J., Di Girolamo, T., Di Giulio, C., Di Pierro, F., Di Venere, L., Diaz, L., Díaz, C., Dib, C., Dickinson, H., Diebold, S., Digel, S., Djannati-Ataï, A., Doert, M., Domínguez, A., Prester, D. Dominis, Donnarumma, I., Dorner, D., Doro, M., Dournaux, J. -L., Downes, T., Drake, G., Drappeau, S., Drass, H., Dravins, D., Drury, L., Dubus, G., Morå, K. Dundas, Durkalec, A., Dwarkadas, V., Ebr, J., Eckner, C., Edy, E., Egberts, K., Einecke, S., Eisch, J., Eisenkolb, F., Ekoume, T. R. N., Eleftheriadis, C., Elsässer, D., Emmanoulopoulos, D., Ernenwein, J. -P., Escarate, P., Eschbach, S., Espinoza, C., Evans, P., Evoli, C., Fairbairn, M., Falceta-Goncalves, D., Falcone, A., Ramazani, V. Fallah, Farakos, K., Farrell, E., Fasola, G., Favre, Y., Fede, E., Fedora, R., Fedorova, E., Fegan, S., Fernandez-Alonso, M., Fernández-Barral, A., Ferrand, G., Ferreira, O., Fesquet, M., Fiandrini, E., Fiasson, A., Filipovic, M., Fink, D., Finley, J. P., Finley, C., Finoguenov, A., Fioretti, V., Fiorini, M., Flores, H., Foffano, L., Föhr, C., Fonseca, M. V., Font, L., Fontaine, G., Fornasa, M., Fortin, P., Fortson, L., Fouque, N., Fraga, B., Franco, F. J., Coromina, L. Freixas, Fruck, C., Fugazza, D., Fujita, Y., Fukami, S., Fukazawa, Y., Fukui, Y., Funk, S., Furniss, A., Füßling, M., Gabici, S., Gadola, A., Gallant, Y., Galloway, D., Gallozzi, S., Garcia, B., Garcia, A., Gil, R. García, López, R. Garcia, Garczarczyk, M., Gardiol, D., Gargano, F., Gargano, C., Garozzo, S., Garrido-Ruiz, M., Gascon, D., Gasparetto, T., Gaté, F., Gaug, M., Gebhardt, B., Gebyehu, M., Geffroy, N., Genolini, B., Ghalumyan, A., Ghedina, A., Ghirlanda, G., Giammaria, P., Gianotti, F., Giebels, B., Giglietto, N., Gika, V., Gimenes, R., Giommi, P., Giordano, F., Giovannini, G., Giro, E., Giroletti, M., Gironnet, J., Giuliani, A., Glicenstein, J. -F., Gnatyk, R., Godinovic, N., Goldoni, P., Gómez, J. L., Gómez-Vargas, G., González, M. M., González, J. M., Gothe, K. S., Gotz, D., Goullon, J., Grabarczyk, T., Graciani, R., Graham, J., Grandi, P., Granot, J., Grasseau, G., Gredig, R., Green, A. J., Greenshaw, T., Grenier, I., Griffiths, S., Grillo, A., Grondin, M. -H., Grube, J., Guarino, V., Guest, B., Gueta, O., Gunji, S., Gyuk, G., Hadasch, D., Hagge, L., Hahn, J., Hahn, A., Hakobyan, H., Hara, S., Hardcastle, M. J., Hassan, T., Haubold, T., Haupt, A., Hayashi, K., Hayashida, M., He, H., Heller, M., Helo, J. C., Henault, F., Henri, G., Hermann, G., Hermel, R., Llorente, J. Herrera, Herrero, A., Hervet, O., Hidaka, N., Hinton, J., Hiroshima, N., Hirotani, K., Hnatyk, B., Hoang, J. K., Hoffmann, D., Hofmann, W., Holder, J., Horan, D., Hörandel, J., Hörbe, M., Horns, D., Horvath, P., Houles, J., Hovatta, T., Hrabovsky, M., Hrupec, D., Huet, J. -M., Hughes, G., Hui, D., Hull, G., Humensky, T. B., Hussein, M., Hütten, M., Iarlori, M., Ikeno, Y., Illa, J. M., Impiombato, D., Inada, T., Ingallinera, A., Inome, Y., Inoue, S., Inoue, T., Inoue, Y., Iocco, F., Ioka, K., Ionica, M., Iori, M., Iriarte, A., Ishio, K., Israel, G. L., Iwamura, Y., Jablonski, C., Jacholkowska, A., Jacquemier, J., Jamrozy, M., Janecek, P., Jankowsky, F., Jankowsky, D., Jansweijer, P., Jarnot, C., Jean, P., Johnson, C. A., Josselin, M., Jung-Richardt, I., Jurysek, J., Kaaret, P., Kachru, P., Kagaya, M., Kakuwa, J., Kalekin, O., Kankanyan, R., Karastergiou, A., Karczewski, M., Karkar, S., Katagiri, H., Kataoka, J., Katarzyński, K., Katz, U., Kawanaka, N., Kaye, L., Kazanas, D., Kelley-Hoskins, N., Khélifi, B., Kieda, D. B., Kihm, T., Kimeswenger, S., Kimura, S., Kisaka, S., Kishida, S., Kissmann, R., Kluźniak, W., Knapen, J., Knapp, J., Knödlseder, J., Koch, B., Kocot, J., Kohri, K., Komin, N., Kong, A., Konno, Y., Kosack, K., Kowal, G., Koyama, S., Kraus, M., Krause, M., Krauß, F., Krennrich, F., Kruger, P., Kubo, H., Kudryavtsev, V., Mezek, G. Kukec, Kumar, S., Kuroda, H., Kushida, J., Kushwaha, P., La Palombara, N., La Parola, V., La Rosa, G., Lahmann, R., Lalik, K., Lamanna, G., Landoni, M., Landriu, D., Landt, H., Lang, R. G., Lapington, J., Laporte, P., Blanc, O. Le, Flour, T. Le, Sidaner, P. Le, Leach, S., Leckngam, A., Lee, S. -H., Lee, W. H., Lees, J. -P., Lefaucheur, J., de Oliveira, M. A. Leigui, Lemoine-Goumard, M., Lenain, J. -P., Leto, G., Lico, R., Limon, M., Lindemann, R., Lindfors, E., Linhoff, L., Lipniacka, A., Lloyd, S., Lohse, T., Lombardi, S., Longo, F., Lopez, M., Lopez-Coto, R., Louge, T., Louis, F., Louys, M., Lucarelli, F., Lucchesi, D., Luque-Escamilla, P. L., Lyard, E., Maccarone, M. C., Maccarone, T., Mach, E., Madejski, G. M., Maier, G., Majczyna, A., Majumdar, P., Makariev, M., Malaguti, G., Malouf, A., Maltezos, S., Malyshev, D., Mandat, D., Maneva, G., Manganaro, M., Mangano, S., Manigot, P., Mannheim, K., Maragos, N., Marano, D., Marcowith, A., Marín, J., Mariotti, M., Marisaldi, M., Markoff, S., Martí, J., Martin, J. -M., Martin, P., Martin, L., Martínez, M., Martínez, G., Martínez, O., Marx, R., Masetti, N., Massimino, P., Mastichiadis, A., Mastropietro, M., Masuda, S., Matsumoto, H., Matthews, N., Mattiazzo, S., Maurin, G., Maxted, N., Mayer, M., Mazin, D., Mazziotta, M. N., Comb, L. Mc, McHardy, I., Medina, C., Melandri, A., Melioli, C., Melkumyan, D., Mereghetti, S., Meunier, J. -L., Meures, T., Meyer, M., Micanovic, S., Michael, T., Michałowski, J., Mievre, I., Miller, J., Minaya, I. A., Mineo, T., Mirabel, F., Miranda, J. M., Mirzoyan, R., Mitchell, A., Mizuno, T., Moderski, R., Mohammed, M., Mohrmann, L., Molijn, C., Molinari, E., Moncada, R., Montaruli, T., Monteiro, I., Mooney, D., Moore, P., Moralejo, A., Morcuende-Parrilla, D., Moretti, E., Mori, K., Morlino, G., Morris, P., Morselli, A., Moscato, F., Motohashi, D., Moulin, E., Mueller, S., Mukherjee, R., Munar, P., Mundell, C., Mundet, J., Murach, T., Muraishi, H., Murase, K., Murphy, A., Nagai, A., Nagar, N., Nagataki, S., Nagayoshi, T., Nagesh, B. K., Naito, T., Nakajima, D., Nakamori, T., Nakamura, Y., Nakayama, K., Naumann, D., Nayman, P., Neise, D., Nellen, L., Nemmen, R., Neronov, A., Neyroud, N., Nguyen, T., Nguyen, T. T., Trung, T. Nguyen, Nicastro, L., Nicolau-Kukliński, J., Niemiec, J., Nieto, D., Nievas-Rosillo, M., Nikołajuk, M., Nishijima, K., Nishikawa, K. -I., Nishiyama, G., Noda, K., Nogues, L., Nolan, S., Nosek, D., Nöthe, M., Novosyadlyj, B., Nozaki, S., Nunio, F., O'Brien, P., Oakes, L., Ocampo, C., Ochoa, J. P., Oger, R., Ohira, Y., Ohishi, M., Ohm, S., Okazaki, N., Okumura, A., Olive, J. -F., Ong, R. A., Orienti, M., Orito, R., Orlati, A., Osborne, J. P., Ostrowski, M., Otte, N., Ou, Z., Ovcharov, E., Oya, I., Ozieblo, A., Padovani, M., Paiano, S., Paizis, A., Palacio, J., Palatiello, M., Palatka, M., Pallotta, J., Panazol, J. -L., Paneque, D., Panter, M., Paoletti, R., Paolillo, M., Papitto, A., Paravac, A., Paredes, J. M., Pareschi, G., Parsons, R. D., Paśko, P., Pavy, S., Pe'er, A., Pech, M., Pedaletti, G., Del Campo, P. Peñil, Perez, A., Pérez-Torres, M. A., Perri, L., Perri, M., Persic, M., Petrashyk, A., Petrera, S., Petrucci, P. -O., Petruk, O., Peyaud, B., Pfeifer, M., Piano, G., Piel, Q., Pieloth, D., Pintore, F., García, C. Pio, Pisarski, A., Pita, S., Pizarro, L., Platos, Ł., Pohl, M., Poireau, V., Pollo, A., Porthault, J., Poutanen, J., Pozo, D., Prandini, E., Prasit, P., Prast, J., Pressard, K., Principe, G., Prokhorov, D., Prokoph, H., Prouza, M., Pruteanu, G., Pueschel, E., Pühlhofer, G., Puljak, I., Punch, M., Pürckhauer, S., Queiroz, F., Quinn, J., Quirrenbach, A., Rafighi, I., Rainò, S., Rajda, P. J., Rando, R., Rannot, R. C., Razzaque, S., Reichardt, I., Reimer, O., Reimer, A., Reisenegger, A., Renaud, M., Reposeur, T., Reville, B., Rezaeian, A. H., Rhode, W., Ribeiro, D., Ribó, M., Richer, M. G., Richtler, T., Rico, J., Rieger, F., Riquelme, M., Ristori, P. R., Rivoire, S., Rizi, V., Rodriguez, J., Fernandez, G. Rodriguez, Vázquez, J. J. Rodríguez, Rojas, G., Romano, P., Romeo, G., Roncadelli, M., Rosado, J., Rosen, S., Lees, S. Rosier, Rousselle, J., Rovero, A. C., Rowell, G., Rudak, B., Rugliancich, A., del Mazo, J. E. Ruíz, Rujopakarn, W., Rulten, C., Russo, F., Saavedra, O., Sabatini, S., Sacco, B., Sadeh, I., Hatlen, E. Sæther, Safi-Harb, S., Sahakian, V., Sailer, S., Saito, T., Sakaki, N., Sakurai, S., Salek, D., Greus, F. Salesa, Salina, G., Sanchez, D., Sánchez-Conde, M., Sandaker, H., Sandoval, A., Sangiorgi, P., Sanguillon, M., Sano, H., Santander, M., Santangelo, A., Santos, E. M., Sanuy, A., Sapozhnikov, L., Sarkar, S., Satalecka, K., Sato, Y., Saturni, F. G., Savalle, R., Sawada, M., Schanne, S., Schioppa, E. J., Schlenstedt, S., Schmidt, T., Schmoll, J., Schneider, M., Schoorlemmer, H., Schovanek, P., Schulz, A., Schussler, F., Schwanke, U., Schwarz, J., Schweizer, T., Schwemmer, S., Sciacca, E., Scuderi, S., Seglar-Arroyo, M., Segreto, A., Seitenzahl, I., Semikoz, D., Sergijenko, O., Serre, N., Servillat, M., Seweryn, K., Shah, K., Shalchi, A., Sharma, M., Shellard, R. C., Shilon, I., Sidoli, L., Sidz, M., Siejkowski, H., Silk, J., Sillanpää, A., Simone, D., Singh, B. B., Sironi, G., Sitarek, J., Sizun, P., Sliusar, V., Slowikowska, A., Smith, A., Sobczyńska, D., Sokolenko, A., Sol, H., Sottile, G., Springer, W., Stahl, O., Stamerra, A., Stanič, S., Starling, R., Staszak, D., Stawarz, Ł., Steenkamp, R., Stefanik, S., Stegmann, C., Steiner, S., Stella, C., Stephan, M., Sternberger, R., Sterzel, M., Stevenson, B., Stodulska, M., Stodulski, M., Stolarczyk, T., Stratta, G., Straumann, U., Stuik, R., Suchenek, M., Suomijarvi, T., Supanitsky, A. D., Suric, T., Sushch, I., Sutcliffe, P., Sykes, J., Szanecki, M., Szepieniec, T., Tagliaferri, G., Tajima, H., Takahashi, K., Takahashi, H., Takahashi, M., Takalo, L., Takami, S., Takata, J., Takeda, J., Tam, T., Tanaka, M., Tanaka, T., Tanaka, Y., Tanaka, S., Tanci, C., Tavani, M., Tavecchio, F., Tavernet, J. -P., Tayabaly, K., Tejedor, L. A., Temme, F., Temnikov, P., Terada, Y., Terrazas, J. C., Terrier, R., Terront, D., Terzic, T., Tescaro, D., Teshima, M., Testa, V., Thoudam, S., Tian, W., Tibaldo, L., Tiengo, A., Tiziani, D., Tluczykont, M., Peixoto, C. J. Todero, Tokanai, F., Tokarz, M., Toma, K., Tomastik, J., Tonachini, A., Tonev, D., Tornikoski, M., Torres, D. F., Torresi, E., Tosti, G., Totani, T., Tothill, N., Toussenel, F., Tovmassian, G., Trakarnsirinont, N., Travnicek, P., Trichard, C., Trifoglio, M., Pujadas, I. Troyano, Tsirou, M., Tsujimoto, S., Tsuru, T., Uchiyama, Y., Umana, G., Uslenghi, M., Vagelli, V., Vagnetti, F., Valentino, M., Vallania, P., Valore, L., Berg, A. M. Van den, van Driel, W., van Eldik, C., van Soelen, B., Vandenbroucke, J., Vanderwalt, J., Varner, G. S., Vasileiadis, G., Vassiliev, V., Vázquez, J. R., Acosta, M. Vázquez, Vecchi, M., Vega, A., Veitch, P., Venault, P., Venter, C., Vercellone, S., Veres, P., Vergani, S., Verzi, V., Vettolani, G. P., Veyssiere, C., Viana, A., Vicha, J., Vigorito, C., Villanueva, J., Vincent, P., Vink, J., Visconti, F., Vittorini, V., Voelk, H., Voisin, V., Vollhardt, A., Vorobiov, S., Vovk, I., Vrastil, M., Vuillaume, T., Wagner, S. J., Wagner, R., Wagner, P., Wakely, S. P., Walstra, T., Walter, R., Ward, M., Ward, J. E., Warren, D., Watson, J. J., Webb, N., Wegner, P., Weiner, O., Weinstein, A., Weniger, C., Werner, F., Wetteskind, H., White, M., White, R., Wierzcholska, A., Wiesand, S., Wijers, R., Wilcox, P., Wilhelm, A., Wilkinson, M., Will, M., Williams, D. A., Winter, M., Wojcik, P., Wolf, D., Wood, M., Wörnlein, A., Wu, T., Yadav, K. K., Yaguna, C., Yamamoto, T., Yamamoto, H., Yamane, N., Yamazaki, R., Yanagita, S., Yang, L., Yelos, D., Yoshida, T., Yoshida, M., Yoshiike, S., Yoshikoshi, T., Yu, P., Zaborov, D., Zacharias, M., Zaharijas, G., Zajczyk, A., Zampieri, L., Zandanel, F., Zanin, R., Sanchez, R. Zanmar, Zaric, D., Zavrtanik, M., Zavrtanik, D., Zdziarski, A. A., Zech, A., Zechlin, H., Zhdanov, V. I., Ziegler, A., Ziemann, J., Ziętara, K., Zink, A., Ziółkowski, J., Zitelli, V., Zoli, A., and Zorn, J.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

List of contributions from the Cherenkov Telescope Array Consortium presented at the 35th International Cosmic Ray Conference, July 12-20 2017, Busan, Korea., Comment: Index of Cherenkov Telescope Array conference proceedings at the ICRC2017, Busan, Korea

Published
2017

46. Very-High-Energy $\gamma$-Ray Observations of the Blazar 1ES 2344+514 with VERITAS

Author

Allen, C., Archambault, S., Archer, A., Benbow, W., Bird, R., Bourbeau, E., Brose, R., Buchovecky, M., Buckley, J. H., Bugaev, V., Cardenzana, J. V, Cerruti, M., Chen, X., Christiansen, J. L., Connolly, M. P., Cui, W., Daniel, M. K., Eisch, J. D., Falcone, A., Feng, Q., Fernandez-Alonso, M., Finley, J. P., Fleischhack, H., Flinders, A., Fortson, L., Furniss, A., Gillanders, G. H., Griffin, S., Grube, J., Hütten, M., Håkansson, N., Hanna, D., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Johnson, C. A., Kaaret, P., Kar, P., Kelley-Hoskins, N., Kertzman, M., Kieda, D., Krause, M., Krennrich, F., Kumar, S., Lang, M. J., Maier, G., McArthur, S., McCann, A., Meagher, K., Moriarty, P., Mukherjee, R., Nguyen, T., Nieto, D., O'Brien, S., de Bhróithe, A. O'Faoláin, Ong, R. A., Otte, A. N., Park, N., Petrashyk, A., 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., Wilhelm, A., and Williams, D. A.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We present very-high-energy $\gamma$-ray observations of the BL Lac object 1ES 2344+514 taken by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) between 2007 and 2015. 1ES 2344+514 is detected with a statistical significance above background of $20.8\sigma$ in $47.2$ hours (livetime) of observations, making this the most comprehensive very-high-energy study of 1ES 2344+514 to date. Using these observations the temporal properties of 1ES 2344+514 are studied on short and long times scales. We fit a constant flux model to nightly- and seasonally-binned light curves and apply a fractional variability test, to determine the stability of the source on different timescales. We reject the constant-flux model for the 2007-2008 and 2014-2015 nightly-binned light curves and for the long-term seasonally-binned light curve at the $> 3\sigma$ level. The spectra of the time-averaged emission before and after correction for attenuation by the extragalactic background light are obtained. The observed time-averaged spectrum above 200 GeV is satisfactorily fitted (${\chi^2/NDF = 7.89/6}$) by a power-law function with index $\Gamma = 2.46 \pm 0.06_{stat} \pm 0.20_{sys} $ and extends to at least 8 TeV. The extragalactic-background-light-deabsorbed spectrum is adequately fit (${\chi^2/NDF = 6.73/6}$) by a power-law function with index $\Gamma = 2.15 \pm 0.06_{stat} \pm 0.20_{sys} $ while an F-test indicates that the power-law with exponential cutoff function provides a marginally-better fit ($\chi^2/NDF $ = $2.56 / 5 $) at the 2.1$\sigma$ level. The source location is found to be consistent with the published radio location and its spatial extent is consistent with a point source., Comment: 7 pages, 2 figures. Published in Monthly Notices of the Royal Astronomical Society

Published
2017
Full Text
View/download PDF

47. Luminous and high-frequency peaked blazars: the origin of the $\gamma$-ray emission from PKS 1424+240

Author

Cerruti, M., Benbow, W., Chen, X., Dumm, J. P., Fortson, L. F., and Shahinyan, K.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The current generation of Cherenkov telescopes, together with Fermi-LAT, have greatly increased our knowledge of $\gamma$-ray blazars. Among them, the high-frequency-peaked BL Lacertae object (HBL) PKS1424+240 (z $\simeq$ 0.6) is the farthest persistent emitter of very-high-energy (VHE; E $\geq$ 100 GeV) $\gamma$-ray photons. Current emission models can satisfactorily reproduce typical blazar emission assuming that the dominant emission process is synchrotron-self-Compton (SSC) in HBLs; and external-inverse-Compton (EIC) in LBLs and FSRQs. Hadronic models are also able to correctly reproduce the $\gamma$-ray emission from blazars, although they are in general disfavoured for bright quasars and rapid flares.The blazar PKS1424+240 is a rare example of a luminous HBL, and we aim to determine which is the emission process most likely responsible for its $\gamma$-ray emission. This will impact more generally our comprehension of blazar emission models, and how they are related to the luminosity of the source and the peak frequency. We investigate different blazar emission models applied to the SED of PKS1424+240. Among leptonic models, we study a 1-zone SSC model, a 2-zone SSC model, and an EIC model. We then investigate a blazar hadronic model, and finally a scenario in which the $\gamma$-ray emission is associated with cascades in the line-of-sight produced by cosmic rays from the source. After a systematic study of the parameter space of the one-zone SSC model, we conclude that this scenario is not compatible with $\gamma$-ray observations of PKS1424+240. A two-zone SSC scenario can alleviate this issue, as well as an EIC solution. For the latter, the external photon field is assumed to be the infra-red radiation from the dusty torus. Alternatively, hadronic models can satisfactorily reproduce the $\gamma$-ray emission from PKS1424+240, both as in-source emission and as cascade emission., Comment: 11 pages, 8 figures; in press in A&A; abstract abridged

Published
2017
Full Text
View/download PDF

48. 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

49. 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

50. 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

Catalog

Books, media, physical & digital resources
See catalog results