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1. A VERITAS/Breakthrough Listen Search for Optical Technosignatures

Author

A. Acharyya, C. B. Adams, A. Archer, P. Bangale, P. Batista, W. Benbow, A. Brill, M. Capasso, M. Errando, A. Falcone, Q. Feng, J. P. Finley, G. M. Foote, L. Fortson, A. Furniss, S. Griffin, W. Hanlon, D. Hanna, O. Hervet, C. E. Hinrichs, J. Hoang, J. Holder, T. B. Humensky, W. Jin, P. Kaaret, M. Kertzman, M. Kherlakian, D. Kieda, T. K. Kleiner, N. Korzoun, S. Kumar, M. J. Lang, M. Lundy, G. Maier, C. E. McGrath, M. J. Millard, H. R. Miller, J. Millis, C. L. Mooney, P. Moriarty, R. Mukherjee, S. O’Brien, R. A. Ong, M. Pohl, E. Pueschel, J. Quinn, K. Ragan, P. T. Reynolds, D. Ribeiro, E. Roache, J. L. Ryan, I. Sadeh, L. Saha, M. Santander, G. H. Sembroski, R. Shang, D. Tak, A. K. Talluri, J. V. Tucci, N. Vazquez, D. A. Williams, S. L. Wong, J. Woo, VERITAS Collaboration, D. DeBoer, H. Isaacson, I. de Pater, D. C. Price, and A. Siemion

Subjects
Technosignatures, Search for extraterrestrial intelligence, Gamma-ray telescopes, Transient detection, Astronomy, QB1-991
Abstract

The Breakthrough Listen Initiative is conducting a program using multiple telescopes around the world to search for “technosignatures”: artificial transmitters of extraterrestrial origin from beyond our solar system. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) Collaboration joined this program in 2018 and provides the capability to search for one particular technosignature: optical pulses of a few nanoseconds in duration detectable over interstellar distances. We report here on the analysis and results of dedicated VERITAS observations of Breakthrough Listen targets conducted in 2019 and 2020 and of archival VERITAS data collected since 2012. Thirty hours of dedicated observations of 136 targets and 249 archival observations of 140 targets were analyzed and did not reveal any signals consistent with a technosignature. The results are used to place limits on the fraction of stars hosting transmitting civilizations. We also discuss the minimum pulse sensitivity of our observations and present VERITAS observations of CALIOP: a space-based pulsed laser on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations. The detection of these pulses with VERITAS, using the analysis techniques developed for our technosignature search, allows a test of our analysis efficiency and serves as an important proof of principle.

Published
2023
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2. Multiwavelength Investigation of γ-Ray Source MGRO J1908+06 Emission Using Fermi-LAT, VERITAS and HAWC

Author

A. Acharyya, C. B. Adams, P. Bangale, J. T. Bartkoske, W. Benbow, J. H. Buckley, J. L. Christiansen, A. J. Chromey, A. Duerr, M. Errando, A. Falcone, Q. Feng, G. M. Foote, L. Fortson, A. Furniss, W. Hanlon, D. Hanna, O. Hervet, C. E. Hinrichs, J. Holder, T. B. Humensky, W. Jin, P. Kaaret, M. Kertzman, D. Kieda, T. K. Kleiner, N. Korzoun, S. Kumar, M. J. Lang, M. Lundy, G. Maier, C. E McGrath, M. J. Millard, J. Millis, C. L. Mooney, P. Moriarty, R. Mukherjee, W. Ning, R. A. Ong, N. Park, M. Pohl, E. Pueschel, J. Quinn, P. L. Rabinowitz, K. Ragan, D. Ribeiro, E. Roache, J. L. Ryan, I. Sadeh, L. Saha, G. H. Sembroski, R. Shang, M. Splettstoesser, A. K. Talluri, J. V. Tucci, J. Valverde, V. V. Vassiliev, A. Weinstein, D. A. Williams, S. L. Wong, J. Woo, The VERITAS Collaboration, R. Alfaro, C. Alvarez, J. C. Arteaga-Velázquez, D. Avila Rojas, R. Babu, E. Belmont-Moreno, A. Bernal, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, J. Cotzomi, S. Coutiño de León, E. De la Fuente, D. Depaoli, N. Di Lalla, R. Diaz Hernandez, M. A. DuVernois, C. Espinoza, K. L. Fan, K. Fang, N. Fraija, J. A. García-González, F. Garfias, M. M. González, J. A. Goodman, S. Groetsch, S. Hernández-Cadena, J. Hinton, D. Huang, F. Hueyotl-Zahuantitla, A. Iriarte, S. Kaufmann, J. Lee, H. León Vargas, A. L. Longinotti, G. Luis-Raya, K. Malone, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, J. A. Morales-Soto, E. Moreno, M. Mostafá, L. Nellen, E. G. Pérez-Pérez, C. D. Rho, D. Rosa-González, H. Salazar, A. Sandoval, M. Schneider, J. Serna-Franco, Y. Son, R. W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, R. Turner, F. Ureña-Mena, E. Varela, X. Wang, H. Zhou, The HAWC Collaboration, J. Eagle, and The Fermi-LAT Collaboration

Subjects
Gamma-ray astronomy, Pulsar wind nebulae, Supernova remnants, Astrophysics, QB460-466
Abstract

This paper investigates the origin of the γ -ray emission from MGRO J1908+06 in the GeV–TeV energy band. By analyzing the data collected by the Fermi Large Area Telescope, the Very Energetic Radiation Imaging Telescope Array System, and High Altitude Water Cherenkov, with the addition of spectral data previously reported by LHAASO, a multiwavelength study of the morphological and spectral features of MGRO J1908+06 provides insight into the origin of the γ -ray emission. The mechanism behind the bright TeV emission is studied by constraining the magnetic field strength, the source age, and the distance through detailed broadband modeling. Both spectral shape and energy-dependent morphology support the scenario that inverse Compton emission of an evolved pulsar wind nebula associated with PSR J1907+0602 is responsible for the MGRO J1908+06 γ -ray emission with a best-fit true age of T = 22 ± 9 kyr and a magnetic field of B = 5.4 ± 0.8 μ G, assuming the distance to the pulsar d _PSR = 3.2 kpc.

Published
2024
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3. A Multiwavelength Study to Decipher the 2017 Flare of the Blazar OJ 287

Author

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

Subjects
Blazars, Active galactic nuclei, Active galaxies, Gamma-ray astronomy, Gamma-ray sources, Astrophysics, QB460-466
Abstract

In 2017 February, 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 the Swift X-ray Telescope. This event coincides with a very-high-energy (VHE) γ -ray outburst that led VERITAS to detect emission above 100 GeV, with a detection significance of 10 σ (from 2016 December 9 to 2017 March 31). The time-averaged VHE γ -ray spectrum was consistent with a soft power law (Γ = −3.81 ± 0.26) and an integral flux corresponding to ∼2.4% that of the Crab Nebula above the same energy. Contemporaneous data from multiple instruments across the electromagnetic spectrum reveal a 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 2017 February peak. The spectral energy distributions during these periods suggest the presence of at least two nonthermal 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.

Published
2024
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4. An Angular Diameter Measurement of β UMa via Stellar Intensity Interferometry with the VERITAS Observatory

Author

A. Acharyya, J. P. Aufdenberg, P. Bangale, J. T. Bartkoske, P. Batista, W. Benbow, A. J. Chromey, J. D. Davis, Q. Feng, G. M. Foote, A. Furniss, W. Hanlon, C. E. Hinrichs, J. Holder, W. Jin, P. Kaaret, M. Kertzman, D. Kieda, T. K. Kleiner, N. Korzoun, T. LeBohec, M. A. Lisa, M. Lundy, N. Matthews, C. E McGrath, M. J. Millard, P. Moriarty, S. Nikkhah, S. O’Brien, R. A. Ong, M. Pohl, E. Pueschel, J. Quinn, P. L. Rabinowitz, K. Ragan, E. Roache, J. G. Rose, J. L. Sackrider, I. Sadeh, L. Saha, G. H. Sembroski, R. Shang, D. Tak, M. Ticoras, J. V. Tucci, D. A. Williams, S. L. Wong, and The VERITAS Collaboration

Subjects
Long baseline interferometry, Fundamental parameters of stars, Astronomy data modeling, Astrophysics, QB460-466
Abstract

We use the Very Energetic Radiation Imaging telescope Array System (VERITAS) imaging air Cherenkov telescope array to obtain the first measured angular diameter of β UMa at visual wavelengths using stellar intensity interferometry (SII) and independently constrain the limb-darkened angular diameter. The age of the Ursa Major moving group has been assessed from the ages of its members, including nuclear member Merak ( β UMa), an A1-type subgiant, by comparing effective temperature and luminosity constraints to model stellar evolution tracks. Previous interferometric limb-darkened angular-diameter measurements of β UMa in the near-infrared (Center for High Angular Resolution Astronomy (CHARA) Array, 1.149 ± 0.014 mas) and mid-infrared (Keck Nuller, 1.08 ± 0.07 mas), together with the measured parallax and bolometric flux, have constrained the effective temperature. This paper presents current VERITAS-SII observation and analysis procedures to derive squared visibilities from correlation functions. We fit the resulting squared visibilities to find a limb-darkened angular diameter of 1.07 ± 0.04 (stat) ± 0.05 (sys) mas, using synthetic visibilities from a stellar atmosphere model that provides a good match to the spectrum of β UMa in the optical wave band. The VERITAS-SII limb-darkened angular diameter yields an effective temperature of 9700 ± 200 ± 200 K, consistent with ultraviolet spectrophotometry, and an age of 390 ± 29 ± 32 Myr, using MESA Isochrones and Stellar Tracks. This age is consistent with 408 ± 6 Myr from the CHARA Array angular diameter.

Published
2024
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5. Multiwavelength Observations of the Blazar PKS 0735+178 in Spatial and Temporal Coincidence with an Astrophysical Neutrino Candidate IceCube-211208A

Author

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

Published
2023
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6. A Multiwavelength Investigation of PSR J2229+6114 and its Pulsar Wind Nebula in the Radio, X-Ray, and Gamma-Ray Bands

Author

I. Pope, K. Mori, M. Abdelmaguid, J. D. Gelfand, S. P. Reynolds, S. Safi-Harb, C. J. Hailey, H. An, NuSTAR Collaboration, P. Bangale, P. Batista, W. Benbow, J. H. Buckley, M. Capasso, J. L. Christiansen, A. J. Chromey, A. Falcone, Q. Feng, J. P. Finley, G. M Foote, G. Gallagher, W. F Hanlon, D. Hanna, O. Hervet, J. Holder, T. B. Humensky, W. Jin, P. Kaaret, M. Kertzman, D. Kieda, T. K. Kleiner, N. Korzoun, F. Krennrich, S. Kumar, M. J. Lang, G. Maier, C. E McGrath, C. L. Mooney, P. Moriarty, R. Mukherjee, S. O’Brien, R. A. Ong, N. Park, S. R. Patel, K. Pfrang, M. Pohl, E. Pueschel, J. Quinn, K. Ragan, P. T. Reynolds, E. Roache, I. Sadeh, L. Saha, G. H. Sembroski, D. Tak, J. V. Tucci, A. Weinstein, D. A. Williams, J. Woo, and VERITAS Collaboration

Subjects
Pulsar wind nebulae, X-ray astronomy, Gamma-ray astronomy, Astrophysics, QB460-466
Abstract

G106.3+2.7, commonly considered to be a composite supernova remnant (SNR), is characterized by a boomerang-shaped pulsar wind nebula (PWN) and two distinct (“head” and “tail”) regions in the radio band. A discovery of very-high-energy gamma-ray emission ( E _γ > 100 GeV) followed by the recent detection of ultrahigh-energy gamma-ray emission ( E _γ > 100 TeV) from the tail region suggests that G106.3+2.7 is a PeVatron candidate. We present a comprehensive multiwavelength study of the Boomerang PWN (100″ around PSR J2229+6114) using archival radio and Chandra data obtained two decades ago, a new NuSTAR X-ray observation from 2020, and upper limits on gamma-ray fluxes obtained by Fermi-LAT and VERITAS observatories. The NuSTAR observation allowed us to detect a 51.67 ms spin period from the pulsar PSR J2229+6114 and the PWN emission characterized by a power-law model with Γ = 1.52 ± 0.06 up to 20 keV. Contrary to the previous radio study by Kothes et al., we prefer a much lower PWN B -field ( B ∼ 3 μ G) and larger distance ( d ∼ 8 kpc) based on (1) the nonvarying X-ray flux over the last two decades, (2) the energy-dependent X-ray size of the PWN resulting from synchrotron burn-off, and (3) the multiwavelength spectral energy distribution (SED) data. Our SED model suggests that the PWN is currently re-expanding after being compressed by the SNR reverse shock ∼1000 yr ago. In this case, the head region should be formed by GeV–TeV electrons injected earlier by the pulsar propagating into the low-density environment.

Published
2023
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7. Multiwavelength Observation Campaign of the TeV Gamma-Ray Binary HESS J0632 + 057 with NuSTAR, VERITAS, MDM, and Swift

Author

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

Published
2021
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8. A Search for TeV Gamma-Ray Emission from Pulsar Tails by VERITAS

Author

W. Benbow, A. Brill, J. H. Buckley, M. Capasso, A. J. Chromey, M. Errando, A. Falcone, K. A Farrell, Q. Feng, J. P. Finley, G. M. Foote, L. Fortson, A. Furniss, A. Gent, C. Giuri, D. Hanna, T. Hassan, O. Hervet, J. Holder, G. Hughes, T. B. Humensky, W. Jin, P. Kaaret, Oleg Kargaltsev, M. Kertzman, D. Kieda, Noel Klingler, S. Kumar, M. J. Lang, M. Lundy, G. Maier, C. E McGrath, P. Moriarty, R. Mukherjee, D. Nieto, M. Nievas-Rosillo, S. O’Brien, R. A. Ong, A. N. Otte, S. Patel, K. Pfrang, M. Pohl, R. R. Prado, J. Quinn, K. Ragan, P. T. Reynolds, D. Ribeiro, G. T. Richards, E. Roache, J. L. Ryan, M. Santander, G. H. Sembroski, R. Shang, Igor Volkov, S. P. Wakely, A. Weinstein, P. Wilcox, and D. A. Williams

Published
2021
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9. Search for Ultraheavy Dark Matter from Observations of Dwarf Spheroidal Galaxies with VERITAS

Author

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

Subjects
Astrophysics and Astronomy, Cosmology and Nongalactic Astrophysics (astro-ph.CO), WIMP, VHE [gamma ray], FOS: Physical sciences, mass [dark matter], GeV, annihilation [dark matter], High Energy Physics - Experiment, High Energy Physics - Experiment (hep-ex), High Energy Physics - Phenomenology (hep-ph), TeV, fluctuation [background], composite, Particle Physics - Phenomenology, High Energy Astrophysical Phenomena (astro-ph.HE), astro-ph.HE, hep-ex, dark matter: mass, imaging, hep-ph, dark matter: annihilation, Astronomy and Astrophysics, observatory, High Energy Physics - Phenomenology, Cherenkov counter, gamma ray: VHE, Space and Planetary Science, astro-ph.CO, ddc:520, background: fluctuation, VERITAS, galaxy, Astrophysics - High Energy Astrophysical Phenomena, Particle Physics - Experiment, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

The astrophysical journal / 1 945(2), 101 (2023). doi:10.3847/1538-4357/acbc7b, 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 by Institute of Physics Publ., London

Published
2023

10. Identifying muon rings in VERITAS data using convolutional neural networks trained on images classified with Muon Hunters 2

Author

Matthew Lundy, A. Brill, M. Capasso, Hugh Dickinson, Manel Errando, T. J. Williamson, S. Kumar, S. Patel, Vladimir Vassiliev, M. J. Lang, David Hanna, P. Moriarty, John L. Quinn, Orel Gueta, donggeun tak, David A. Williams, Michael Laraia, Sameer Patel, Jodi Christiansen, P. Wilcox, Thomas Brian Humensky, C. E. McGrath, Alasdair E. Gent, R.R. Prado, Avery Archer, K. Ragan, M. Kertzman, C. Adams, M. Nievas-Rosillo, J. H. Buckley, Reshmi Mukherjee, David Kieda, Tobias Kleiner, A. J. Chromey, A. D. Falcone, Philip Kaaret, James M. Ryan, Wystan Benbow, Lucy Fortson, A. N. Otte, R. A. Ong, C. Giuri, K. A. Farrell, G. M. Foote, Deivid Ribeiro, Stephen Serjeant, E. Roache, Martin Pohl, Binita Hona, Jamie Holder, G. H. Sembroski, Daniel Nieto, K. Pfrang, S. O'Brien, Kevin Flanagan, Amanda Weinstein, Gary Gillanders, Marcos Santander, Q. Feng, I. Sadeh, Darryl Wright, R. Shang, W. Jin, Olivier Hervet, Gernot Maier, P. T. Reynolds, Amy Furniss, and E. Pueschel

Subjects
Muon, Physics::Instrumentation and Detectors, Calibration (statistics), Computer science, business.industry, Pattern recognition, Convolutional neural network, law.invention, Image (mathematics), Hough transform, Telescope, Identification (information), law, Computer Science::Computer Vision and Pattern Recognition, False positive paradox, High Energy Physics::Experiment, Artificial intelligence, business
Abstract

Muons from extensive air showers appear as rings in images taken with imaging atmospheric Cherenkov telescopes, such as VERITAS. These muon-ring images are used for the calibration of the VERITAS telescopes, however the calibration accuracy can be improved with a more efficient muon-identification algorithm. Convolutional neural networks (CNNs) are used in many state-of-the-art image-recognition systems and are ideal for muon image identification, once trained on a suitable dataset with labels for muon images. However, by training a CNN on a dataset labelled by existing algorithms, the performance of the CNN would be limited by the suboptimal muon-identification efficiency of the original algorithms. Muon Hunters 2 is a citizen science project that asks users to label grids of VERITAS telescope images, stating which images contain muon rings. Each image is labelled 10 times by independent volunteers, and the votes are aggregated and used to assign a `muon' or `non-muon' label to the corresponding image. An analysis was performed using an expert-labelled dataset in order to determine the optimal vote percentage cut-offs for assigning labels to each image for CNN training. This was optimised so as to identify as many muon images as possible while avoiding false positives. The performance of this model greatly improves on existing muon identification algorithms, identifying approximately 30 times the number of muon images identified by the current algorithm implemented in VEGAS (VERITAS Gamma-ray Analysis Suite), and roughly 2.5 times the number identified by the Hough transform method, along with significantly outperforming a CNN trained on VEGAS-labelled data.

Published
2021

11. Multi-Messenger observations of the Fermi-LAT blazar 4FGL J0658.6+0636 consistent with an IceCube high-energy neutrino

Author

David R. Williams, Antoine Kouchner, K. A. Farrell, Alasdair E. Gent, V. V. Vassiliev, Fabian Schüssler, H. A. Peña-Herazo, Georgios Paraschos, R. Shang, D. S. Hanna, Q. Feng, John L. Quinn, D. Ribeiro, Daniel Nieto, A. Brill, Giacomo Bonnoli, M. Kertzman, Lucy Fortson, Yong Sheng, Olivier Hervet, T. B. Humensky, Francesco Massaro, S. O'Brien, Alessio Berti, M. J. Lang, donggeun tak, Teddy Cheung, Suvi Gezari, Joern Wilms, A. D. Falcone, P. T. Reynolds, Miguel Perez-Torres, Andrea Tramacere, Reshmi Mukherjee, G. M. Foote, Binita Hona, C. Giuri, Raniere de Menezes, P. Kaaret, I. Sadeh, Frank J. Masci, Emilio Fernandez-Garcia, W. Jin, Wystan Benbow, Uwe Bach, R. R. Prado, P. Moriarty, Jonas Heßdörfer, M. Pohl, Matthias Kadler, Steven Hämmerich, Gernot Maier, G. H. Sembroski, Andrea Gokus, R. A. Ong, M. Capasso, Ivan Agudo, Marcos Santander, C. E. McGrath, T. J. Williamson, A. J.R. Weinstein, E. Roache, A. Archer, Jorge Otero-Santos, Simone Garrappa, Alex Kraus, G. H. Gillanders, A. J. Castro-Tirado, Alexis Coleiro, Jodi Christiansen, Jamie Holder, K. Ragan, Meenakshi Rajagopal, A. N. Otte, Alessandro Paggi, K. Pfrang, Orel Gueta, Marcello Giroletti, Cristina Nanci, Javier Moldon, M. Nievas-Rosillo, Elisa Bernardini, C. Adams, Werner Colmar, Y. D. Hu, J. A. Ryan, Richard Walters, M. Lundy, Florian Eppel, Tobias Kleiner, R. Sanchez-Ramirez, J. H. Buckley, A. J. Chromey, Amy Furniss, Charlotte Ward, Konstancja Satalecka, E. Pueschel, Manel Errando, Sara Buson, S. Kumar, S. Patel, M. D. Caballero-Garcia, and Marco Ajello

Subjects
Physics, High energy, Astrophysics, Neutrino, Blazar, Fermi Gamma-ray Space Telescope
Published
2021

12. Status of the VERITAS Stellar Intensity Interferometry (VSII) System

Author

P. Moriarty, Alasdair E. Gent, James Ryan, R. Shang, Daniel Nieto, E. Roache, M. Capasso, M. Kertzman, T. J. Williamson, Davis Jonathan, David R. Williams, K. Ragan, S. O'Brien, Wystan Benbow, M. J. Lang, Marcos Santander, P. Kaaret, M. Pohl, Reshmi Mukherjee, C. E. McGrath, I. Sadeh, A. Brill, K Matthews Nolan, A. J.R. Weinstein, Jamie Holder, C. Giuri, Q. Feng, John L. Quinn, A. Archer, D. Ribeiro, M. Nievas-Rosillo, Sameer Patel, Orel Gueta, A. D. Falcone, Manel Errando, G. H. Sembroski, Gernot Maier, S. Kumar, R. R. Prado, D. S. Hanna, C. B. Adams, David Kieda, T. B. Humensky, S. Patel, LeBohec Tugdual, R. A. Ong, G. H. Gillanders, Olivier Hervet, K. A. Farrell, V. V. Vassiliev, Lisa Mike, Lucy Fortson, Jodi Christiansen, Tobias Kleiner, G. M. Foote, J. H. Buckley, A. J. Chromey, donggeun tak, A. N. Otte, K. Pfrang, W. Jin, M. Lundy, Binita Hona, Amy Furniss, E. Pueschel, and P. T. Reynolds

Subjects
Physics, Interferometry, Astronomy, Intensity (physics)
Published
2021

13. Very High Energy Gamma-ray Emission from the Binary System LS I +61 303

Author

G. M. Foote, S. O'Brien, W. Jin, Tobias Kleiner, R. Shang, Orel Gueta, R. R. Prado, P. Kaaret, P. T. Reynolds, E. Pueschel, John L. Quinn, I. Sadeh, C. B. Adams, James Ryan, D. Ribeiro, David R. Williams, M. Pohl, Gernot Maier, Jodi Christiansen, Q. Feng, T. B. Humensky, M. Lundy, Marcos Santander, Lucy Fortson, P. Moriarty, Olivier Hervet, C. E. McGrath, M. Capasso, M. Kertzman, A. J.R. Weinstein, A. Brill, A. N. Otte, Daniel Nieto, David Kieda, T. J. Williamson, K. Pfrang, Manel Errando, S. Kumar, R. A. Ong, S. Patel, G. H. Sembroski, J. H. Buckley, M. Nievas-Rosillo, Binita Hona, D. S. Hanna, K. A. Farrell, V. V. Vassiliev, Sameer Patel, donggeun tak, Amy Furniss, A. Archer, E. Roache, A. J. Chromey, G. H. Gillanders, Reshmi Mukherjee, C. Giuri, Alasdair E. Gent, K. Ragan, M. J. Lang, A. D. Falcone, Jamie Holder, and Wystan Benbow

Subjects
Physics, High energy, Gamma ray, Binary system, Computational physics
Published
2021

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

Author

S. O'Brien, donggeun tak, E. Roache, K. A. Farrell, V. V. Vassiliev, John L. Quinn, D. Ribeiro, J. H. Buckley, K. Ragan, P. Kaaret, A. Archer, A. J. Chromey, M. Nievas-Rosillo, G. H. Gillanders, Reshmi Mukherjee, David Kieda, Jodi Christiansen, C. Giuri, James M. Ryan, M. Kertzman, Olivier Hervet, Amy Furniss, A. Brill, I. Sadeh, Lucy Fortson, Marcos Santander, Binita Hona, D. S. Hanna, M. J. Lang, E. Pueschel, Wystan Benbow, A. D. Falcone, Orel Gueta, Q. Feng, P. Moriarty, M. Capasso, W. Jin, Daniel Nieto, Gernot Maier, Martin Pohl, T. J. Williamson, A. N. Otte, C. E. McGrath, K. Pfrang, A. J.R. Weinstein, R. Shang, P. T. Reynolds, G. M. Foote, Jamie Holder, R. A. Ong, R. R. Prado, David A. Williams, Tobias Kleiner, G. H. Sembroski, J. A. Ryan, M. Lundy, C. Adams, T. B. Humensky, Manel Errando, S. Kumar, S. Patel, and Alasdair E. Gent

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Supermassive black hole, Astrophysics::High Energy Astrophysical Phenomena, Galactic Center, Astrophysics::Instrumentation and Methods for Astrophysics, Gamma ray, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Light curve, law.invention, Telescope, Sagittarius A, law, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics, Cherenkov radiation, Zenith
Abstract

The Galactic Center region hosts a variety of powerful astronomical sources and rare astrophysical processes that emit a large flux of non-thermal radiation. We present the analysis of the very-high-energy gamma-ray emission above 2 TeV of the region around the Galactic Center known as the Central Molecular Zone using 125 hours of data taken with the VERITAS imaging-atmospheric Cherenkov telescope between 2010 and 2018. This analysis employs new shower reconstruction algorithms and instrument response functions optimized for data taken at large zenith angles such as the Galactic Center sources. We report positions and spectra for point sources VER J1745-290, G0.9+0.1, and HESS J1746-285, along with a light curve for VER J1745-290, the brightest source in the region consistent with the position of the supermassive black hole Sagittarius A*. We also measure the spectrum of the diffuse emission from the Galactic Center ridge region, which has been claimed as evidence of a Galactic PeVatron., Contribution to the Proceedings of the 37th International Cosmic Ray Conference (ICRC 2021), Berlin, Germany

Published
2021

15. The VERITAS-Stellar Intensity Interferometry (VSII) survey of Stellar Diameters

Author

James Ryan, Wystan Benbow, Mike Lisa, G. M. Foote, P. Moriarty, C. B. Adams, Lucy Fortson, Amy Furniss, Q. Feng, R. A. Ong, P. T. Reynolds, M. Capasso, M. Kertzman, Manel Errando, E. Pueschel, Orel Gueta, Daniel Nieto, T. J. Williamson, S. Kumar, T. B. Humensky, M. Nievas-Rosillo, G. H. Sembroski, S. Patel, Nolan Matthews, Sameer Patel, Alasdair E. Gent, J. H. Buckley, A. N. Otte, D. S. Hanna, Marcos Santander, M. Lundy, Tugdual LeBohec, P. Kaaret, A. Archer, K. Pfrang, Gernot Maier, A. J. Chromey, S. O'Brien, Binita Hona, C. E. McGrath, donggeun tak, Olivier Hervet, David R. Williams, Reshmi Mukherjee, A. Brill, G. H. Gillanders, A. J.R. Weinstein, Jonathan Davis, Jodi Christiansen, I. Sadeh, C. Giuri, R. Shang, Tobias Kleiner, E. Roache, David Kieda, M. Pohl, K. Ragan, K. A. Farrell, V. V. Vassiliev, John L. Quinn, D. Ribeiro, R. R. Prado, W. Jin, Jamie Holder, M. J. Lang, and A. D. Falcone

Subjects
Telescope, Physics, Interferometry, Stars, Cardinal point, Optical wavelength, law, IACT, Astrophysics, Cherenkov radiation, Intensity (physics), law.invention
Abstract

The VERITAS Imaging Air Cherenkov Telescope (IACT) array was augmented in 2019 with high-speed focal plane electronics to allow its use for Stellar Intensity Interferometry (SII) observations. Since January 2019, The VERITAS Stellar Interferometer (VSII) recorded more than 250 hours of moonlit observations on 39 different bright stars and binary systems ($m_V < 3.74$ ) at an effective optical wavelength of 416 nm. These observations resulted in the measurement of the diameters of several stars with better than 5\% resolution. This talk will describe the status of the VSII survey and analysis.

Published
2021

16. Very High Energy Gamma-ray Emission from the Binary System LS I +61 303

Author

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

Published
2021
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17. Status of the VERITAS Stellar Intensity Interferometry (VSII) System

Author

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

Published
2021
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18. The VERITAS-Stellar Intensity Interferometry (VSII) survey of Stellar Diameters

Author

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

Published
2021
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19. Multi-Wavelength Observation Campaign of the TeV Gamma-Ray Binary HESS J0632+057 with NuSTAR, VERITAS, MDM, and Swift

Author

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

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 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
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20. An Archival Search for Neutron-star Mergers in Gravitational Waves and Very-high-energy Gamma Rays

Author

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

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Gravitational wave, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, IACT, Gamma-ray astronomy, Cherenkov Telescope Array, 030226 pharmacology & pharmacy, 01 natural sciences, LIGO, 03 medical and health sciences, Neutron star, 0302 clinical medicine, Space and Planetary Science, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, Gamma-ray burst, 010303 astronomy & astrophysics, Cherenkov radiation
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

21. VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations

Author

A. Acharyya, C. B. Adams, A. Archer, P. Bangale, W. Benbow, A. Brill, J. L. Christiansen, A. J. Chromey, M. Errando, A. Falcone, Q. Feng, J. P. Finley, G. M. Foote, L. Fortson, A. Furniss, G. Gallagher, W. Hanlon, D. Hanna, O. Hervet, C. E. Hinrichs, J. Hoang, J. Holder, W. Jin, M. N. Johnson, P. Kaaret, M. Kertzman, D. Kieda, T. K. Kleiner, N. Korzoun, F. Krennrich, M. J. Lang, M. Lundy, G. Maier, C. E McGrath, M. J. Millard, J. Millis, C. L. Mooney, P. Moriarty, R. Mukherjee, S. O’Brien, R. A. Ong, M. Pohl, E. Pueschel, J. Quinn, K. Ragan, P. T. Reynolds, D. Ribeiro, E. Roache, I. Sadeh, A. C. Sadun, L. Saha, M. Santander, G. H. Sembroski, R. Shang, M. Splettstoesser, A. K. Talluri, J. V. Tucci, V. V. Vassiliev, D. A. Williams, S. L. Wong, The VERITAS Collaboration, Talvikki Hovatta, Svetlana G. Jorstad, Sebastian Kiehlmann, Anne Lähteenmäki, Ioannis Liodakis, Alan P. Marscher, Walter Max-Moerbeck, Anthony C. S. Readhead, Rodrigo Reeves, Paul S. Smith, and Merja Tornikoski

Subjects
Gamma-rays, High energy astrophysics, Blazars, Active galactic nuclei, Jets, Astrophysics, QB460-466
Abstract

We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on 2015 May 15 with the Fermi-Large Area Telescope (LAT). A combined 5 hr VERITAS exposure on May 16 and 18 resulted in a strong 13 σ detection with a differential photon spectral index, Γ = 3.8 ± 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target-of-opportunity observations with Swift, optical photometry, polarimetry, and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of τ _obs = 6.2 ± 0.9 hr, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cutoff. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.

Published
2023
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22. VERITAS and Fermi-LAT Constraints on the Gamma-Ray Emission from Superluminous Supernovae SN2015bn and SN2017egm

Author

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

Subjects
Shocks, Gamma-rays, Particle astrophysics, Supernovae, Magnetars, Millisecond pulsars, Astrophysics, QB460-466
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.

Published
2023
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