Author: "Ribeiro D." - Searchworks@Jio Institute Digital Library Search Results

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1,598 results on '"Ribeiro D."'

1. The cool brown dwarf Gliese 229 B is a close binary

Author: Xuan, Jerry W., Mérand, A., Thompson, W., Zhang, Y., Lacour, S., Blakely, D., Mawet, D., Oppenheimer, R., Kammerer, J., Batygin, K., Sanghi, A., Wang, J., Ruffio, J. -B., Liu, M. C., Knutson, H., Brandner, W., Burgasser, A., Rickman, E., Bowens-Rubin, R., Salama, M., Balmer, W., Blunt, S., Bourdarot, G., Caselli, P., Chauvin, G., Davies, R., Drescher, A., Eckart, A., Eisenhauer, F., Fabricius, M., Feuchtgruber, H., Finger, G., Schreiber, N. M. Förster, Garcia, P., Genzel, R., Gillessen, S., Grant, S., Hartl, M., Haußmann, F., Henning, T., Hinkley, S., Hönig, S. F., Horrobin, M., Houllé, M., Janson, M., Kervella, P., Kral, Q., Kreidberg, L., Bouquin, J. -B. Le, Lutz, D., Mang, F., Marleau, G. -D., Millour, F., More, N., Nowak, M., Ott, T., Otten, G., Paumard, T., Rabien, S., Rau, C., Ribeiro, D. C., Bordoni, M. Sadun, Sauter, J., Shangguan, J., Shimizu, T. T., Sykes, C., Soulain, A., Spezzano, S., Straubmeier, C., Stolker, T., Sturm, E., Subroweit, M., Tacconi, L. J., van Dishoeck, E. F., Vigan, A., Widmann, F., Wieprecht, E., Winterhalder, T. O., and Woillez, J.
Subjects: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: Owing to their similarities with giant exoplanets, brown dwarf companions of stars provide insights into the fundamental processes of planet formation and evolution. From their orbits, several brown dwarf companions are found to be more massive than theoretical predictions given their luminosities and the ages of their host stars (e.g. Brandt et al. 2021, Cheetham et al. 2018, Li et al. 2023). Either the theory is incomplete or these objects are not single entities. For example, they could be two brown dwarfs each with a lower mass and intrinsic luminosity (Brandt et al. 2021, Howe et al. 2024). The most problematic example is Gliese 229 B (Nakajima et al. 1995, Oppenheimer et al. 1995), which is at least 2-6 times less luminous than model predictions given its dynamical mass of $71.4\pm0.6$ Jupiter masses ($M_{\rm Jup}$) (Brandt et al. 2021). We observed Gliese 229 B with the GRAVITY interferometer and, separately, the CRIRES+ spectrograph at the Very Large Telescope. Both sets of observations independently resolve Gliese 229 B into two components, Gliese 229 Ba and Bb, settling the conflict between theory and observations. The two objects have a flux ratio of $0.47\pm0.03$ at a wavelength of 2 $\mu$m and masses of $38.1\pm1.0$ and $34.4\pm1.5$ $M_{\rm Jup}$, respectively. They orbit each other every 12.1 days with a semimajor axis of 0.042 astronomical units (AU). The discovery of Gliese 229 BaBb, each only a few times more massive than the most massive planets, and separated by 16 times the Earth-moon distance, raises new questions about the formation and prevalence of tight binary brown dwarfs around stars., Comment: Published in Nature. The Version of Record of this article is located at https://www.nature.com/articles/s41586-024-08064-x
Published: 2024
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2. The GRAVITY young stellar object survey XIV : Investigating the magnetospheric accretion-ejection processes in S CrA N

Author: GRAVITY Collaboration, Nowacki, H., Perraut, K., Labadie, L., Bouvier, J., Dougados, C., Benisty, M., Wojtczak, J. A., Soulain, A., Alecian, E., Brandner, W., Garatti, A. Caratti o, Lopez, R. Garcia, Ganci, V., Sánchez-Bermúdez, J., Berger, J. -P., Bourdarot, G., Caselli, P., Clénet, Y., Davies, R., Drescher, A., Eckart, A., Eisenhauer, F., Fabricius, M., Feuchtgruber, H., Förster-Schreiber, N. M., Garcia, P., Gendron, E., Genzel, R., Gillessen, S., Grant, S., Henning, T., Jocou, L., Kervella, P., Kurtovic, N., Lacour, S., Lapeyrère, V., Bouquin, J. -B. Le, Lutz, D., Mang, F., Ott, T., Paumard, T., Perrin, G., Rabien, S., Ribeiro, D., Bordoni, M. Sadun, Scheithauer, S., Shangguan, J., Shimizu, T., Spezzano, S., Straubmeier, C., Sturm, E., Tacconi, L., van Dishoeck, E., Vincent, F., and Widmann, F.
Subjects: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract: The dust- and gas-rich protoplanetary disks around young stellar systems play a key role in star and planet formation. While considerable progress has recently been made in probing these disks on large scales of a few tens of astronomical units (au), the central au needs to be more investigated. We aim at unveiling the physical processes at play in the innermost regions of the strongly accreting T Tauri Star S CrA N by means of near-infrared interferometric observations. The K-band continuum emission is well reproduced with an azimuthally-modulated dusty ring. As the star alone cannot explain the size of this sublimation front, we propose that magnetospheric accretion is an important dust-heating mechanism leading to this continuum emission. The differential analysis of the Hydrogen Br$\gamma$ line is in agreement with radiative transfer models combining magnetospheric accretion and disk winds. Our observations support an origin of the Br$\gamma$ line from a combination of (variable) accretion-ejection processes in the inner disk region.
Published: 2024
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3. Results from ON-OFF analysis of the Neutrinos-Angra detector

Author: Kemp, E., Santos, W. V., Anjos, J. C., Chimenti, P., Gonzalez, L. F. G., Guedes, G. P., Lima Jr., H. P., Nóbrega, R. A., Pepe, I. M., and Ribeiro, D. B. S.
Subjects: High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Abstract: The Neutrinos Angra Experiment, a water-based Cherenkov detector, is located at the Angra dos Reis nuclear power plant in Brazil. Designed to detect electron antineutrinos produced in the nuclear reactor, the primary objective of the experiment is to demonstrate the feasibility of monitoring reactor activity using an antineutrino detector. This effort aligns with the International Atomic Energy Agency (IAEA) program to identify potential and novel technologies applicable to nonproliferation safeguards. Operating on the surface presents challenges such as high noise rates, necessitating the development of very sensitive, yet small-scale detectors. These conditions make the Angra experiment an excellent platform for both developing the application and gaining expertise in new technologies and analysis methods. The detector employs a water-based target doped with gadolinium to enhance its sensitivity to antineutrinos. In this work, we describe the main features of the detector and the electronics chain, including front-end and data acquisition components. We detail the data acquisition strategies and the methodologies applied for signal processing and event selection. Preliminary physics results suggest that the detector can reliably monitor reactor operations by detecting the inverse beta decay induced by electron antineutrinos from the reactor.
Published: 2024

4. 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

5. 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

6. High contrast at short separation with VLTI/GRAVITY: Bringing Gaia companions to light

Author: Pourré, N., Winterhalder, T. O., Bouquin, J. -B. Le, Lacour, S., Bidot, A., Nowak, M., Maire, A. -L., Mouillet, D., Babusiaux, C., Woillez, J., Abuter, R., Amorim, A., Asensio-Torres, R., Balmer, W. O., Benisty, M., Berger, J. -P., Beust, H., Blunt, S., Boccaletti, A., Bonnefoy, M., Bonnet, H., Bordoni, M. S., Bourdarot, G., Brandner, W., Cantalloube, F., Caselli, P., Charnay, B., Chauvin, G., Chavez, A., Choquet, E., Christiaens, V., Clénet, Y., Foresto, V. Coudé du, Cridland, A., Davies, R., Defrère, D., Dembet, R., Dexter, J., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Schreiber, N. M. Föster, Garcia, P., Lopez, R. Garcia, Gendron, E., Genzel, R., Gillessen, S., Girard, J. H., Gonte, F., Grant, S., Haubois, X., Heißel, G., Henning, Th., Hinkley, S., Hippler, S., Hönig, S. F., Houllé, M., Hubert, Z., Jocou, L., Kammerer, J., Kenworthy, M., Keppler, M., Kervella, P., Kreidberg, L., Kurtovic, N. T., Lagrange, A. -M., Lapeyrère, V., Lutz, D., Mang, F., Marleau, G. -D., Mérand, A., Millour, F., Mollière, P., Monnier, J. D., Mordasini, C., Nasedkin, E., Oberti, S., Ott, T., Otten, G. P. L., Paladini, C., Paumard, T., Perraut, K., Perrin, G., Pfuhl, O., Pueyo, L., Ribeiro, D. C., Rickman, E., Rustamkulov, Z., Shangguan, J., Shimizu, T., Sing, D., Soulez, F., Stadler, J., Stolker, T., Straub, O., Straubmeier, C., Sturm, E., Sykes, C., Tacconi, L. J., van Dishoeck, E. F., Vigan, A., Vincent, F., von Fellenberg, S. D., Wang, J., Widmann, F., Yazici, S., Collaboration, the GRAVITY, Abad, J. A., Carpentier, E. Aller, Alonso, J., Andolfato, L., Barriga, P., Beuzit, J. -L., Bourget, P., Brast, R., Caniguante, L., Cottalorda, E., Darré, P., Delabre, B., Delboulbé, A., Delplancke-Ströbele, F., Donaldson, R., Dorn, R., Dupuy, C., Egner, S., Fischer, G., Frank, C., Fuenteseca, E., Gitton, P., Guerlet, T., Guieu, S., Gutierrez, P., Haguenauer, P., Haimerl, A., Heritier, C. T., Huber, S., Hubin, N., Jolley, P., Kirchbauer, J. -P., Kolb, J., Kosmalski, J., Krempl, P., Louarn, M. Le, Lilley, P., Lopez, B., Magnard, Y., Mclay, S., Meilland, A., Meister, A., Moulin, T., Pasquini, L., Paufique, J., Percheron, I., Pettazzi, L., Phan, D., Pirani, W., Quentin, J., Rakich, A., Ridings, R., Reyes, J., Rochat, S., Schmid, C., Schuhler, N., Shchekaturov, P., Seidel, M., Soenke, C., Stadler, E., Stephan, C., Suárez, M., Todorovic, M., Valdes, G., Verinaud, C., Zins, G., Zúñiga-Fernández, S., and Collaboration, the NAOMI
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract: Since 2019, GRAVITY has provided direct observations of giant planets and brown dwarfs at separations of down to 95 mas from the host star. Some of these observations have provided the first direct confirmation of companions previously detected by indirect techniques (astrometry and radial velocities). We want to improve the observing strategy and data reduction in order to lower the inner working angle of GRAVITY in dual-field on-axis mode. We also want to determine the current limitations of the instrument when observing faint companions with separations in the 30-150 mas range. To improve the inner working angle, we propose a fiber off-pointing strategy during the observations to maximize the ratio of companion-light-to-star-light coupling in the science fiber. We also tested a lower-order model for speckles to decouple the companion light from the star light. We then evaluated the detection limits of GRAVITY using planet injection and retrieval in representative archival data. We compare our results to theoretical expectations. We validate our observing and data-reduction strategy with on-sky observations; first in the context of brown dwarf follow-up on the auxiliary telescopes with HD 984 B, and second with the first confirmation of a substellar candidate around the star Gaia DR3 2728129004119806464. With synthetic companion injection, we demonstrate that the instrument can detect companions down to a contrast of $8\times 10^{-4}$ ($\Delta \mathrm{K}= 7.7$ mag) at a separation of 35 mas, and a contrast of $3\times 10^{-5}$ ($\Delta \mathrm{K}= 11$ mag) at 100 mas from a bright primary (K<6.5), for 30 min exposure time. With its inner working angle and astrometric precision, GRAVITY has a unique reach in direct observation parameter space. This study demonstrates the promising synergies between GRAVITY and Gaia for the confirmation and characterization of substellar companions., Comment: 16 pages, 14 figures. Submitted to A&A
Published: 2024

7. Broadband Multi-wavelength Properties of M87 during the 2018 EHT Campaign including a Very High Energy Flaring Episode

Author: Algaba, J. C., Balokovic, M., Chandra, S., Cheong, W. Y., Cui, Y. Z., D'Ammando, F., Falcone, A. D., Ford, N. M., Giroletti, M., Goddi, C., Gurwell, M. A., Hada, K., Haggard, D., Jorstad, S., Kaur, A., Kawashima, T., Kerby, S., Kim, J. Y., Kino, M., Kravchenko, E. V., Lee, S. S., Lu, R. S., Markoff, S., Michail, J., Neilsen, J., Nowak, M. A., Principe, G., Ramakrishnan, V., Ripperda, B., Sasada, M., Savchenko, S. S., Sheridan, C., Akiyama, K., Alberdi, A., Alef, W., Anantua, R., Asada, K., Azulay, R., Bach, U., Baczko, A. -K., Ball, D., Bandyopadhyay, B., Barrett, J., Bauböck, M., Benson, B. A., Bintley, D., Blackburn, L., Blundell, R., Bouman, K. L., Bower, G. C., Boyce, H., Bremer, M., Brissenden, R., Britzen, S., Broderick, A. E., Broguiere, D., Bronzwaer, T., Bustamante, S., Carlstrom, J. E., Chael, A., Chan, C. -K., Chang, D. O., Chatterjee, K., Chatterjee, S., Chen, M. -T., Chen, Y., Cheng, X., Cho, I., Christian, P., Conroy, N. S., Conway, J. E., Crawford, T. M., Crew, G. B., Cruz-Osorio, A., Dahale, R., Davelaar, J., De Laurentis, M., Deane, R., Dempsey, J., Desvignes, G., Dexter, J., Dhruv, V., Dihingia, I. K., Doeleman, S. S., Dzib, S. A., Eatough, R. P., Emami, R., Falcke, H., Farah, J., Fish, V. L., Fomalont, E., Ford, H. A., Foschi, M., Fraga-Encinas, R., Freeman, W. T., Friberg, P., Fromm, C. M., Fuentes, A., Galison, P., Gammie, C. F., García, R., Gentaz, O., Georgiev, B., Gold, R., Gómez-Ruiz, A. I., Gómez, J. L., Gu, M., Hesper, R., Heumann, D., Ho, L. C., Ho, P., Honma, M., Huang, C. -W. L., Huang, L., Hughes, D. H., Ikeda, S., Impellizzeri, C. M. V., Inoue, M., Issaoun, S., James, D. J., Jannuzi, B. T., Janssen, M., Jeter, B., Jiang, W., Jiménez-Rosales, A., Johnson, M. D., Jones, A. C., Joshi, A. V., Jung, T., Karuppusamy, R., Keating, G. K., Kettenis, M., Kim, D. -J., Kim, J., Koay, J. Y., Kocherlakota, P., Kofuji, Y., Koch, P. M., Koyama, S., Kramer, C., Kramer, J. A., Kramer, M., Krichbaum, T. P., Kuo, C. -Y., La Bella, N., Levis, A., Li, Z., Lico, R., Lindahl, G., Lindqvist, M., Lisakov, M., Liu, J., Liu, K., Liuzzo, E., Lo, W. -P., Lobanov, A. P., Loinard, L., Lonsdale, C. J., Lowitz, A. E., MacDonald, N. R., Mao, J., Marchili, N., Marrone, D. P., Marscher, A. P., Martí-Vidal, I., Matsushita, S., Matthews, L. D., Medeiros, L., Menten, K. M., Mizuno, I., Mizuno, Y., Montgomery, J., Moran, J. M., Moriyama, K., Moscibrodzka, M., Mulaudzi, W., Müller, C., Müller, H., Mus, A., Musoke, G., Myserlis, I., Nagai, H., Nagar, N. M., Nair, D. G., Nakamura, M., Narayanan, G., Natarajan, I., Nathanail, A., Fuentes, S. Navarro, Ni, C., Oh, J., Okino, H., Olivares, H., Oyama, T., Özel, F., Palumbo, D. C. M., Paraschos, G. Filippos, Park, J., Parsons, H., Patel, N., Pen, U. -L., Pesce, D. W., Piétu, V., PopStefanija, A., Porth, O., Prather, B., Psaltis, D., Pu, H. -Y., Rao, R., Rawlings, M. G., Raymond, A. W., Rezzolla, L., Ricarte, A., Roelofs, F., Romero-Cañizales, C., Ros, E., Roshanineshat, A., Rottmann, H., Roy, A. L., Ruiz, I., Ruszczyk, C., Rygl, K. L. J., Sánchez, S., Sánchez-Argüelles, D., Sánchez-Portal, M., Satapathy, K., Savolainen, T., Schloerb, F. P., Schonfeld, J., Schuster, K. -F., Shao, L., Shen, Z., Small, D., Sohn, B. W., SooHoo, J., Salas, L. D. Sosapanta, Souccar, K., Stanway, J. S., Sun, H., Tazaki, F., Tetarenko, A. J., Tiede, P., Tilanus, R. P. J., Titus, M., Toma, K., Torne, P., Toscano, T., Traianou, E., Trent, T., Trippe, S., Turk, M., van Bemmel, I., van Langevelde, H. J., van Rossum, D. R., Vos, J., Wagner, J., Ward-Thompson, D., Wardle, J., Washington, J. E., Weintroub, J., Wharton, R., Wielgus, M., Wiik, K., Witzel, G., Wondrak, M. F., Wong, G. N., Wu, Q., Yadlapalli, N., Yamaguchi, P., Yfantis, A., Yoon, D., Young, A., Younsi, Z., Yu, W., Yuan, F., Yuan, Y. -F., Zensus, J. A., Zhang, S., Zhao, G. -Y., Zhao, S. -S., Bellazzini, R., Berenji, B., Bissaldi, E., Blandford, R. D., Bonino, R., Bruel, P., Cameron, R. A., Caraveo, P. A., Cavazzuti, E., Cheung, C. C., Ciprini, S., Orestano, P. Cristarella, Cutini, S., Di Lalla, N., Dinesh, A., Di Venere, L., Domínguez, A., Fegan, S. J., Franckowiak, A., Fukazawa, Y., Fusco, P., Gargano, F., Gasbarra, C., Germani, S., Giliberti, M., Grenier, I. A., Hays, E., Horan, D., Kuss, M., Larsson, S., Liodakis, I., Longo, F., Loparco, F., Lovellette, M. N., Maldera, S., Mazziotta, M. N., Mereu, I., Michelson, P. F., Mirabal, N., Mizuno, T., Monzani, M. E., Morselli, A., Negro, M., Omodei, N., Orlando, E., Persic, M., Rainò, S., Rani, B., Reimer, A., Reimer, O., Sánchez-Conde, M., Parkinson, P. M. Saz, Sgrò, C., Siskind, E. J., Spinelli, P., Suson, D. J., Tajima, H., Torres, D. F., Zaharijas, G., Aharonian, F., Benkhali, F. Ait, Aschersleben, J., Ashkar, H., Backes, M., Martins, V. Barbosa, Batzofin, R., Becherini, Y., Berge, D., Böttcher, M., Boisson, C., Bolmont, J., de Lavergne, M. de Bony, Borowska, J., Bouyahiaoui, M., Bradascio, F., Brose, R., Brown, A., Bruno, B., Bulik, T., Burger-Scheidlin, C., Casanova, S., Cecil, R., Celic, J., Cerruti, M., Chand, T., Chen, A., Chibueze, J., Chibueze, O., Czerny, T., Dainotti, M., Dubus, F., Dumm, J., D'Urso, G., Drouhin, A., Durouchoux, P., Fabbian, D., Franczak, D., Funk, M., Gabanyi, J., Gaggero, G., Garcia, N., Geiger, A., Giorgi, M. G., Gleeson, S., Gonzalez, S., Gauthier, G. T., Grasso, P., Hovatta, T., Hyman, J., Kaaret, C., Kirk, D., Lal, S., Lesch, T. M., Lohmann, K., Massaro, C., Mayer, M., Meintjes, P. J., Miral, E., Mirra, A., Neronov, J., Padovani, E., Paccagnella, F., Parisi, E., Piotrowska, A., Pohl, S., Puga, G., Ramirez, L. R., Reville, S., Rowell, D. S., Rudge, M., Rybka, G., Schlenstedt, M. S., Seo, E. S., Svirski, J., Taylor, J. R., Torres, F., Tsujimoto, K., Tosti, F., Volpi, S., Walraven, N. A., Welker, L., Zietkiewicz, M., Abdalla, G., Aleva, C., Benkhali, H. A. Ait, Aldous, M., Amin, M., Aschieri, M. A., de Deus, E., Santos, J. de Los, Fontanot, D., Jorfi, S., Levens, P., Zwart, A. E. E., Oliviero, S., Puglisi, D., Thiel, M., Zaharijas, C., Amaral, F., Boella, L., Holincheck, L., Queiroz, R., Sofue, H., Tellis, G., Wagner, G., Wierzcholska, A., Zacharias, M., Zdziarski, A. A., Zech, A., Zywucka, N., Abe, S., Abhir, J., Abhishek, A., Acciari, V. A., Aguasca-Cabot, A., Agudo, I., Aniello, T., Ansoldi, S., Antonelli, L. A., Engels, A. Arbet, Arcaro, C., Artero, M., Asano, K., Babic, A., de Almeida, U. Barres, Barrio, J. A., Batkovic, I., Bautista, A., Baxter, J., González, J. Becerra, Bednarek, W., Bernardini, E., Bernete, J., Berti, A., Besenrieder, J., Bigongiari, C., Biland, A., Blanch, O., Bonnoli, G., Bosnjak, Z., Bronzini, E., Burelli, I., Busetto, G., Campoy-Ordaz, A., Carosi, A., Carosi, R., Carretero-Castrillo, M., Castro-Tirado, A. J., Cerasole, D., Ceribella, G., Chai, Y., Cifuentes, A., 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., de Menezes, R., Delfino, M., Delgado, J., Mendez, C. Delgado, Di Pierro, F., Di Tria, R., Prester, D. Dominis, Donini, A., Dorner, D., Doro, M., Elsaesser, D., Escudero, J., Fariña, L., Fattorini, A., Foffano, L., Font, L., Fröse, S., Fukami, S., López, R. J. García, Garczarczyk, M., Gasparyan, S., Gaug, M., Paiva, J. G. Giesbrecht, Giglietto, N., Giordano, F., Gliwny, P., Godinovic, N., Gradetzke, T., Grau, R., Green, D., Green, J. G., Günther, P., Hadasch, D., Hahn, A., Hassan, T., Heckmann, L., Llorente, J. Herrera, Hrupec, D., Imazawa, R., Ishio, K., Martínez, I. Jiménez, Jormanainen, J., Kayanoki, T., Kerszberg, D., Kluge, G. W., Kobayashi, Y., Kouch, P. M., Kubo, H., Kushida, J., Laínez, M., Lamastra, A., Leone, F., Lindfors, E., Lombardi, S., 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., Manganaro, M., Mangano, S., Mannheim, K., Mariotti, M., Martínez, M., Martínez-Chicharro, M., Mas-Aguilar, A., Mazin, D., Menchiari, S., Mender, S., Miceli, D., Miener, T., Miranda, J. M., Mirzoyan, R., González, M. Molero, Molina, E., Mondal, H. A., Moralejo, A., Morcuende, D., Nakamori, T., Nanci, C., Neustroev, V., Nickel, L., Rosillo, M. Nievas, Nigro, C., Nikolic, L., Nilsson, K., Nishijima, K., Ekoume, T. Njoh, Noda, K., Nozaki, S., Ohtani, Y., Okumura, A., Otero-Santos, J., Paiano, S., Paneque, D., Paoletti, R., Paredes, J. M., Peresano, M., Pihet, M., Pirola, G., Podobnik, F., Moroni, P. G. Prada, Prandini, E., Priyadarshi, C., Ribó, M., Rico, J., Righi, C., Sahakyan, N., Saito, T., Saturni, F. G., Schmidt, K., Schmuckermaier, F., Schubert, J. L., Schweizer, T., Sciaccaluga, A., Silvestri, G., Sitarek, J., Sliusar, V., Sobczynska, D., Spolon, A., Stamerra, A., Strišković, J., Strom, D., Strzys, M., Suda, Y., Suutarinen, S., Takahashi, M., Takeishi, R., Tavecchio, F., Temnikov, P., Terauchi, K., Terzic, T., Teshima, M., Truzzi, S., Tutone, A., Ubach, S., van Scherpenberg, J., Acosta, M. Vazquez, Ventura, S., Verna, G., Viale, I., Vigorito, C. F., Vitale, V., Vovk, I., Walter, R., Will, M., Wunderlich, C., Yamamoto, T., Acharyya, A., Adams, C. B., Bangale, P., Bartkoske, J. T., Benbow, W., Christiansen, J. L., Duerr, A., Errando, M., Feng, Q., Foote, G. M., Fortson, L., Furniss, A., Hanlon, W., 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., Krennrich, F., Kumar, S., Lang, M. J., Lundy, M., Maier, G., McGrath, C. E., Millard, M. J., Mooney, C. L., Moriarty, P., Mukherjee, R., Ning, W., O'Brien, S., Ong, R. A., 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., Talluri, A. K., Tucci, J. V., Valverde, J., Vassiliev, V. V., Williams, D. A., Wong, S. L., Chen, Z., Cui, L., Hirota, T., Li, B., Li, G., Liu, Q., Liu, X., Liu, Z., Ma, J., Niinuma, K., Ro, H., Sakai, N., Sawada-Satoh, S., Wajima, K., Wang, J., Wang, N., Xia, B., Yan, H., Yonekura, Y., Zhang, H., Zhao, R., Zhong, W., group, The Event Horizon Telescope - Multi-wavelength science working, Collaboration, The Event Horizon Telescope, Collaboration, The Fermi Large Area Telescope, Collaboration, H. E. S. S., Collaboration, MAGIC, Collaboration, VERITAS, and Collaboration, EAVN
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract: The nearby elliptical galaxy M87 contains one of the only two supermassive black holes whose emission surrounding the event horizon has been imaged by the Event Horizon Telescope (EHT). In 2018, more than two dozen multi-wavelength (MWL) facilities (from radio to gamma-ray energies) took part in the second M87 EHT campaign. The goal of this extensive MWL campaign was to better understand the physics of the accreting black hole M87*, the relationship between the inflow and inner jets, and the high-energy particle acceleration. Understanding the complex astrophysics is also a necessary first step towards performing further tests of general relativity. The MWL campaign took place in April 2018, overlapping with the EHT M87* observations. We present a new, contemporaneous spectral energy distribution (SED) ranging from radio to very high energy (VHE) gamma-rays, as well as details of the individual observations and light curves. We also conduct phenomenological modelling to investigate the basic source properties. We present the first VHE gamma-ray flare from M87 detected since 2010. The flux above 350 GeV has more than doubled within a period of about 36 hours. We find that the X-ray flux is enhanced by about a factor of two compared to 2017, while the radio and millimetre core fluxes are consistent between 2017 and 2018. We detect evidence for a monotonically increasing jet position angle that corresponds to variations in the bright spot of the EHT image. Our results show the value of continued MWL monitoring together with precision imaging for addressing the origins of high-energy particle acceleration. While we cannot currently pinpoint the precise location where such acceleration takes place, the new VHE gamma-ray flare already presents a challenge to simple one-zone leptonic emission model approaches, and emphasises the need for combined image and spectral modelling., Comment: 46 pages, 23 figures, accepted by Astronomy & Astrophysics on August. 29, 2024
Published: 2024
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8. Astrometric detection of a Neptune-mass candidate planet in the nearest M-dwarf binary system GJ65 with VLTI/GRAVITY

Author: GRAVITY Collaboration, Abuter, R., Amorim, A., Benisty, M., Berger, J-P., Bonnet, H., Bourdarot, G., Bourget, P., Brandner, W., Clénet, Y., Davies, R., Delplancke-Ströbele, F., Dembet, R., Drescher, A., Eckart, A., Eisenhauer, F., Feuchtgruber, H., Finger, G., Förster-Schreiber, N. M., Garcia, P., Garcia-Lopez, R., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Hartl, M., Haubois, X., Haussmann, F., Henning, T., Hippler, S., Horrobin, M., Jochum, L., Jocou, L., Kaufer, A., Kervella, P., Lacour, S., Lapeyrère, V., Bouquin, J. B. Le, Ledoux, C., Léna, P., Lutz, D., Mang, F., Mérand, A., More, N., Nowak, M., Ott, T., Paumard, T., Perraut, K., Perrin, G., Pfuhl, O., Rabien, S., Ribeiro, D. C., Bordoni, M. Sadun, Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Tacconi, L. J., Tristram, K. R. W, Vincent, F., von Fellenberg, S., Widmann, F., Wieprecht, E., Woillez, J., Yazici, S., and Zins, G.
Subjects: Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract: The detection of low-mass planets orbiting the nearest stars is a central stake of exoplanetary science, as they can be directly characterized much more easily than their distant counterparts. Here, we present the results of our long-term astrometric observations of the nearest binary M-dwarf Gliese 65 AB (GJ65), located at a distance of only 2.67 pc. We monitored the relative astrometry of the two components from 2016 to 2023 with the VLTI/GRAVITY interferometric instrument. We derived highly accurate orbital parameters for the stellar system, along with the dynamical masses of the two red dwarfs. The GRAVITY measurements exhibit a mean accuracy per epoch of 50-60 microarcseconds in 1.5h of observing time using the 1.8m Auxiliary Telescopes. The residuals of the two-body orbital fit enable us to search for the presence of companions orbiting one of the two stars (S-type orbit) through the reflex motion they imprint on the differential A-B astrometry. We detected a Neptune-mass candidate companion with an orbital period of p = 156 +/- 1 d and a mass of m = 36 +/- 7 Mearth. The best-fit orbit is within the dynamical stability region of the stellar pair. It has a low eccentricity, e = 0.1 - 0.3, and the planetary orbit plane has a moderate-to-high inclination of i > 30{\deg} with respect to the stellar pair, with further observations required to confirm these values. These observations demonstrate the capability of interferometric astrometry to reach microarcsecond accuracy in the narrow-angle regime for planet detection by reflex motion from the ground. This capability offers new perspectives and potential synergies with Gaia in the pursuit of low-mass exoplanets in the solar neighborhood., Comment: Corresponding authors: G.Bourdarot, P.Kervella, O.Pfuhl. Accepted in A&A Letters
Published: 2024

9. Four-of-a-kind? Comprehensive atmospheric characterisation of the HR 8799 planets with VLTI/GRAVITY

Author: Nasedkin, E., Mollière, P., Lacour, S., Nowak, M., Kreidberg, L., Stolker, T., Wang, J. J., Balmer, W. O., Kammerer, J., Shangguan, J., Abuter, R., Amorim, A., Asensio-Torres, R., Benisty, M., Berger, J. -P., Beust, H., Blunt, S., Boccaletti, A., Bonnefoy, M., Bonnet, H., Bordoni, M. S., Bourdarot, G., Brandner, W., Cantalloube, F., Caselli, P., Charnay, B., Chauvin, G., Chavez, A., Choquet, E., Christiaens, V., Clénet, Y., Foresto, V. Coudé du, Cridland, A., Davies, R., Dembet, R., Dexter, J., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Schreiber, N. M. Förster, Garcia, P., Lopez, R. Garcia, Gendron, E., Genzel, R., Gillessen, S., Girard, J. H., Grant, S., Haubois, X., Heißel, G., Henning, Th., Hinkley, S., Hippler, S., Houllé, M., Hubert, Z., Jocou, L., Keppler, M., Kervella, P., Kurtovic, N. T., Lagrange, A. -M., Lapeyrère, V., Bouquin, J. -B. Le, Lutz, D., Maire, A. -L., Mang, F., Marleau, G. -D., Mérand, A., Monnier, J. D., Mordasini, C., Ott, T., Otten, G. P. P. L., Paladini, C., Paumard, T., Perraut, K., Perrin, G., Pfuhl, O., Pourré, N., Pueyo, L., Ribeiro, D. C., Rickman, E., Ruffio, J. B., Rustamkulov, Z., Shimizu, T., Sing, D., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Tacconi, L. J., van Dishoeck, E. F., Vigan, A., Vincent, F., von Fellenberg, S. D., Widmann, F., Winterhalder, T. O., Woillez, J., Yazici, S., and Collaboration, the GRAVITY
Subjects: Astrophysics - Earth and Planetary Astrophysics
Abstract: With four companions at separations from 16 to 71 au, HR 8799 is a unique target for direct imaging, presenting an opportunity for the comparative study of exoplanets with a shared formation history. Combining new VLTI/GRAVITY observations obtained within the ExoGRAVITY program with archival data, we perform a systematic atmospheric characterisation of all four planets. We explore different levels of model flexibility to understand the temperature structure, chemistry and clouds of each planet using both petitRADTRANS atmospheric retrievals and fits to self-consistent radiative-convective equilibrium models. Using Bayesian Model Averaging to combine multiple retrievals, we find that the HR 8799 planets are highly enriched in metals, with [M/H] $\gtrsim$1, and have stellar to super-stellar C/O ratios. The C/O ratio increases with increasing separation from $0.55^{+0.12}_{-0.10}$ for d to $0.78^{+0.03}_{-0.04}$ for b, with the exception of the innermost planet which has a C/O ratio of $0.87\pm0.03$. By retrieving a quench pressure and using a disequilibrium chemistry model we derive vertical mixing strengths compatible with predictions for high-metallicity, self-luminous atmospheres. Bayesian evidence comparisons strongly favour the presence of HCN in HR 8799 c and e, as well as CH$_{4}$ in HR 8799 c, with detections at $>5\sigma$ confidence. All of the planets are cloudy, with no evidence for patchiness. The clouds of c, d and e are best fit by silicate clouds lying above a deep iron cloud layer, while the clouds of the cooler HR 8799 b are more likely composed of Na$_{2}$S. With well defined atmospheric properties, future exploration of this system is well positioned to unveil further detail in these planets, extending our understanding of the composition, structure, and formation history of these siblings., Comment: 45 pages, 25 figures, accepted by Astronomy & Astrophysics
Published: 2024
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10. Combining Gaia and GRAVITY: Characterising five new Directly Detected Substellar Companions

Author: Winterhalder, T. O., Lacour, S., Mérand, A., Maire, A. -L., Kammerer, J., Stolker, T., Pourré, N., Babusiaux, C., Abuter, R., Amorim, A., Asensio-Torres, R., Balmer, W. O., Benisty, M., Berger, J. -P., Beust, H., Blunt, S., Boccaletti, A., Bonnefoy, M., Bonnet, H., Bordoni, M. S., Bourdarot, G., Brandner, W., Cantalloube, F., Caselli, P., Charnay, B., Chauvin, G., Chavez, A., Choquet, E., Christiaens, V., Clénet, Y., Foresto, V. Coudé du, Cridland, A., Davies, R., Dembet, R., Dexter, J., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Schreiber, N. M. Förster, Garcia, P., Lopez, R. Garcia, Gardner, T., Gendron, E., Genzel, R., Gillessen, S., Girard, J. H., Grant, S., Haubois, X., Heißel, G., Henning, Th., Hinkley, S., Hippler, S., Houllé, M., Hubert, Z., Jocou, L., Keppler, M., Kervella, P., Kreidberg, L., Kurtovic, N. T., Lagrange, A. -M., Lapeyrère, V., Bouquin, J. -B. Le, Lutz, D., Mang, F., Marleau, G. -D., Mollière, P., Monnier, J. D., Mordasini, C., Mouillet, D., Nasedkin, E., Nowak, M., Ott, T., Otten, G. P. P. L., Paladini, C., Paumard, T., Perraut, K., Perrin, G., Pfuhl, O., Pueyo, L., Ribeiro, D. C., Rickman, E., Rustamkulov, Z., Shangguan, J., Shimizu, T., Sing, D., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Tacconi, L. J., van Dishoeck, E. F., Vigan, A., Vincent, F., von Fellenberg, S. D., Wang, J. J., Widmann, F., Woillez, J., and Yazıcı, Ş.
Subjects: Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract: Precise mass constraints are vital for the characterisation of brown dwarfs and exoplanets. Here we present how the combination of data obtained by Gaia and GRAVITY can help enlarge the sample of substellar companions with measured dynamical masses. We show how the Non-Single-Star (NSS) two-body orbit catalogue contained in Gaia DR3 can be used to inform high-angular-resolution follow-up observations with GRAVITY. Applying the method presented in this work to eight Gaia candidate systems, we detect all eight predicted companions, seven of which were previously unknown and five are of a substellar nature. Among the sample is Gaia DR3 2728129004119806464 B, which - detected at an angular separation of (34.01 $\pm$ 0.15) mas from the host - is the closest substellar companion ever imaged. This translates to a semi-major axis of (0.938 $\pm$ 0.023) AU. WT 766 B, detected at a greater angular separation, was confirmed to be on an orbit exhibiting an even smaller semi-major axis of (0.676 $\pm$ 0.008) AU. The GRAVITY data were then used to break the host-companion mass degeneracy inherent to the Gaia NSS orbit solutions as well as to constrain the orbital solutions of the respective target systems. Knowledge of the companion masses enabled us to further characterise them in terms of their ages, effective temperatures, and radii via the application of evolutionary models. The inferred ages exhibit a distinct bias towards values younger than what is to be expected based on the literature. The results serve as an independent validation of the orbital solutions published in the NSS two-body orbit catalogue and show that the combination of astrometric survey missions and high-angular-resolution direct imaging holds great promise for efficiently increasing the sample of directly imaged companions in the future, especially in the light of Gaia's upcoming DR4 and the advent of GRAVITY+., Comment: Accepted for publication in Astronomy and Astrophysics
Published: 2024
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11. Dark Matter Line Searches with the Cherenkov Telescope Array

Author: Abe, S., Abhir, J., Abhishek, A., Acero, F., Acharyya, A., Adam, R., Aguasca-Cabot, A., Agudo, I., Aguirre-Santaella, A., Alfaro, J., Alfaro, R., Alvarez-Crespo, N., Batista, R. Alves, Amans, J. -P., Amato, E., Ambrosi, G., Angel, L., Aramo, C., Arcaro, C., Arnesen, T. T. H., Arrabito, L., Asano, K., Ascasibar, Y., Aschersleben, J., Ashkar, H., Backes, M., Baktash, A., Balazs, C., Balbo, M., Larriva, A. Baquero, Martins, V. Barbosa, de Almeida, U. Barres, Barrio, J. A., Batković, I., Batzofin, R., Baxter, J., González, J. Becerra, Beck, G., Benbow, W., Berge, D., Bernardini, E., Bernete, J., Bernlöhr, K., Berti, A., Bertucci, B., Bhattacharjee, P., Bhattacharyya, S., Bigongiari, C., Biland, A., Bissaldi, E., Biteau, J., Blanch, O., Blazek, J., Bocchino, F., Boisson, C., Bolmont, J., Bonnoli, G., Bonollo, A., Bordas, P., Bosnjak, Z., Bottacini, E., Böttcher, M., Bringmann, T., Bronzini, E., Brose, R., Brown, A. M., Brunelli, G., Bulgarelli, A., Bulik, T., Burelli, I., Burmistrov, L., Burton, M., Buscemi, M., Bylund, T., Cailleux, J., Campoy-Ordaz, A., Cantlay, B. K., Capasso, G., Caproni, A., Capuzzo-Dolcetta, R., Caraveo, P., Caroff, S., Carosi, A., Carosi, R., Carquin, E., Carrasco, M. -S., Cassol, F., Castaldini, L., Castrejon, N., Castro-Tirado, A. J., Cerasole, D., Cerruti, M., Chadwick, P. M., Chaty, S., Chen, A. W., Chernyakova, M., Chiavassa, A., Chudoba, J., Chytka, L., Cicciari, G. M., Cifuentes, A., Araujo, C. H. Coimbra, Colapietro, M., Conforti, V., Conte, F., Contreras, J. L., Costa, A., Costantini, H., Cotter, G., Cristofari, P., Cuevas, O., Curtis-Ginsberg, Z., D'Amico, G., D'Ammando, F., Dai, S., Dalchenko, M., Dazzi, F., De Angelis, A., de Lavergne, M. de Bony, De Caprio, V., Pino, E. M. de Gouveia Dal, De Lotto, B., De Lucia, M., de Menezes, R., de Naurois, M., de Souza, V., del Peral, L., del Valle, M. V., Giler, A. G. Delgado, Mengual, J. Delgado, Delgado, C., Dell'aiera, M., della Volpe, D., Depaoli, D., Di Girolamo, T., Di Piano, A., Di Pierro, F., Di Tria, R., Di Venere, L., Díaz, C., Diebold, S., Dinesh, A., Djuvsland, J., Dominik, R. M., Prester, D. Dominis, Donini, A., Dorner, D., Dörner, J., Doro, M., Dournaux, J. -L., Duangchan, C., Dubos, C., Ducci, L., Dwarkadas, V. V., Ebr, J., Eckner, C., Egberts, K., Einecke, S., Elsässer, D., Emery, G., Errando, M., Escanuela, C., Escarate, P., Godoy, M. Escobar, Escudero, J., Esposito, P., Ettori, S., Falceta-Goncalves, D., Fedorova, E., Fegan, S., Feng, Q., Ferrand, G., Ferrarotto, F., Fiandrini, E., Fiasson, A., Filipovic, M., Fioretti, V., Fiori, M., Foffano, L., Guiteras, L. Font, Fontaine, G., Fröse, S., Fukazawa, Y., Fukui, Y., Furniss, A., Galanti, G., Galaz, G., Galelli, C., Gallozzi, S., Gammaldi, V., Garczarczyk, M., Gasbarra, C., Gasparrini, D., Ghalumyan, A., Gianotti, F., Giarrusso, M., Paiva, J. G. Giesbrecht Formiga, Giglietto, N., Giordano, F., Giuffrida, R., Glicenstein, J. -F., Glombitza, J., Goldoni, P., González, J. M., González, M. M., Coelho, J. Goulart, Gradetzke, T., Granot, J., Grasso, D., Grau, R., Gréaux, L., Green, D., Green, J. G., Grolleron, G., Guedes, L. M. V., Gueta, O., Hackfeld, J., Hadasch, D., Hamal, P., Hanlon, W., Hara, S., Harvey, V. M., Hassan, T., Hayashi, K., Heß, B., Heckmann, L., Heller, M., Cadena, S. Hernández, Hervet, O., Hinton, J., Hiroshima, N., Hnatyk, B., Hnatyk, R., Hofmann, W., Holder, J., Horan, D., Horvath, P., Hovatta, T., Hrabovsky, M., Hrupec, D., Iarlori, M., Inada, T., Incardona, F., Inoue, S., Inoue, Y., Iocco, F., Iori, M., Ishio, K., Jamrozy, M., Janecek, P., Jankowsky, F., Jean, P., Quiles, J. Jimenez, Jin, W., Juramy-Gilles, C., Jurysek, J., Kagaya, M., Kalekin, O., Karas, V., Katagiri, H., Kataoka, J., Kaufmann, S., Kazanas, D., Kerszberg, D., Kieda, D. B., Kleiner, T., Kluge, G., Kobayashi, Y., Kohri, K., Komin, N., Kornecki, P., Kosack, K., Kowal, G., Kubo, H., Kushida, J., La Barbera, A., La Palombara, N., Láinez, M., Lamastra, A., Lapington, J., Laporte, P., Lazarević, S., Lazendic-Galloway, J., Lemoine-Goumard, M., Lenain, J. -P., Leone, F., Leonora, E., Leto, G., Lindfors, E., Linhoff, M., Liodakis, I., Lipniacka, A., Lombardi, S., Longo, F., López-Coto, R., López-Moya, M., López-Oramas, A., Loporchio, S., Bahilo, J. Lozano, Luque-Escamilla, P. L., Macias, O., Majumdar, P., Mallamaci, M., Malyshev, D., Mandat, D., Manicò, G., Mariotti, M., Márquez, I., Marquez, P., Marsella, G., Martí, J., Martínez, G. A., Martínez, M., Martinez, O., Marty, C., Mas-Aguilar, A., Mastropietro, M., Mazin, D., Menchiari, S., Mestre, E., Meunier, J. -L., Meyer, D. M. -A., Meyer, M., Miceli, D., Miceli, M., Michailidis, M., Michałowski, J., Miener, T., Miranda, J. M., Mitchell, A., Mizote, M., Mizuno, T., Moderski, R., Molero, M., Molfese, C., Molina, E., Montaruli, T., Moralejo, A., Morcuende, D., Morselli, A., Moulin, E., Zamanillo, V. Moya, Munari, K., Murach, T., Muraczewski, A., Muraishi, H., Nakamori, T., Nayak, A., Nemmen, R., Neto, J. P., Nickel, L., Niemiec, J., Nieto, D., Rosillo, M. Nievas, Nikołajuk, M., Nikolić, L., Nishijima, K., Noda, K., Nosek, D., Novotny, V., Nozaki, S., Ohishi, M., Ohtani, Y., Okumura, A., Olive, J. -F., Ong, R. A., Orienti, M., Orito, R., Orlandini, M., Orlando, E., Orlando, S., Ostrowski, M., Otero-Santos, J., Oya, I., Pagano, I., Pagliaro, A., Palatiello, M., Panebianco, G., Paneque, D., Pantaleo, F. R., Paredes, J. M., Parmiggiani, N., Patricelli, B., Pe'er, A., Pech, M., Pecimotika, M., Pensec, U., Peresano, M., Pérez-Romero, J., Persic, M., Peters, K. P., Petruk, O., Piano, G., Pierre, E., Pietropaolo, E., Pihet, M., Pinchbeck, L., Pirola, G., Pittori, C., Plard, C., Podobnik, F., Pohl, M., Pollet, V., Ponti, G., Prandini, E., Principe, G., Priyadarshi, C., Produit, N., Prouza, M., Pueschel, E., Pühlhofer, G., Pumo, M. L., Queiroz, F., Quirrenbach, A., Rainò, S., Rando, R., Razzaque, S., Regeard, M., Reimer, A., Reimer, O., Reisenegger, A., Rhode, W., Ribeiro, D., Ribó, M., Ricci, C., Richtler, T., Rico, J., Rieger, F., Riitano, L., Rizi, V., Roache, E., Fernandez, G. Rodriguez, Frías, M. D. Rodríguez, Rodríguez-Vázquez, J. J., Romano, P., Romeo, G., Rosado, J., de Leon, A. Rosales, Rowell, G., Rudak, B., Ruiter, A. J., Rulten, C. B., Sadeh, I., Saha, L., Saito, T., Salzmann, H., Sánchez-Conde, M., Sandaker, H., Sangiorgi, P., Sano, H., Santander, M., Santos-Lima, R., Sapienza, V., Šarić, T., Sarkar, A., Sarkar, S., Saturni, F. G., Savarese, S., Scherer, A., Schiavone, F., Schipani, P., Schleicher, B., Schovanek, P., Schubert, J. L., Schwanke, U., Arroyo, M. Seglar, Seitenzahl, I. R., Sergijenko, O., Servillat, M., Siegert, T., Siejkowski, H., Siqueira, C., Sliusar, V., Slowikowska, A., Sol, H., Spencer, S. T., Spiga, D., Stamerra, A., Stanič, S., Starecki, T., Starling, R., Stawarz, Ł., Steppa, C., Hatlen, E. Sæther, Stolarczyk, T., Strišković, J., Suda, Y., Świerk, P., Tajima, H., Tak, D., Takahashi, M., Takeishi, R., Tavernier, T., Tejedor, L. A., Terauchi, K., Teshima, M., Testa, V., Tian, W. W., Tibaldo, L., Tibolla, O., Peixoto, C. J. Todero, Torradeflot, F., Torres, D. F., Tosti, G., Tothill, N., Toussenel, F., Tramacere, A., Travnicek, P., Tripodo, G., Trois, A., Truzzi, S., Tutone, A., Vaclavek, L., Vacula, M., Vallania, P., Vallés, R., van Eldik, C., van Scherpenberg, J., Vandenbroucke, J., Vassiliev, V., Acosta, M. Vázquez, Vecchi, M., Ventura, S., Vercellone, S., Verna, G., Viana, A., Viaux, N., Vigliano, A., Vignatti, J., Vigorito, C. F., Villanueva, J., Visentin, E., Vitale, V., Vodeb, V., Voisin, V., Voitsekhovskyi, V., Vorobiov, S., Voutsinas, G., Vovk, I., Vuillaume, T., Wagner, S. J., Walter, R., White, M., White, R., Wierzcholska, A., Will, M., Williams, D. A., Wohlleben, F., Wolter, A., Yamamoto, T., Yang, L., Yoshida, T., Yoshikoshi, T., Zaharijas, G., Zampieri, L., Sanchez, R. Zanmar, Zavrtanik, D., Zavrtanik, M., Zdziarski, A. A., Zech, A., Zhang, W., Zhdanov, V. I., Ziętara, K., Živec, M., and Zuriaga-Puig, J.
Subjects: High Energy Physics - Phenomenology, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
Abstract: Monochromatic gamma-ray signals constitute a potential smoking gun signature for annihilating or decaying dark matter particles that could relatively easily be distinguished from astrophysical or instrumental backgrounds. We provide an updated assessment of the sensitivity of the Cherenkov Telescope Array (CTA) to such signals, based on observations of the Galactic centre region as well as of selected dwarf spheroidal galaxies. We find that current limits and detection prospects for dark matter masses above 300 GeV will be significantly improved, by up to an order of magnitude in the multi-TeV range. This demonstrates that CTA will set a new standard for gamma-ray astronomy also in this respect, as the world's largest and most sensitive high-energy gamma-ray observatory, in particular due to its exquisite energy resolution at TeV energies and the adopted observational strategy focussing on regions with large dark matter densities. Throughout our analysis, we use up-to-date instrument response functions, and we thoroughly model the effect of instrumental systematic uncertainties in our statistical treatment. We further present results for other potential signatures with sharp spectral features, e.g.~box-shaped spectra, that would likewise very clearly point to a particle dark matter origin., Comment: 44 pages JCAP style (excluding author list and references), 19 figures; minor changes to match published version
Published: 2024
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12. A catalogue of dual-field interferometric binary calibrators

Author: Nowak, M., Lacour, S., Abuter, R., Amorim, A., Asensio-Torres, R., Balmer, W. O., Benisty, M., Berger, J. -P., Beust, H., Blunt, S., Boccaletti, A., Bonnefoy, M., Bonnet, H., Bordoni, M. S., Bourdarot, G., Brandner, W., Cantalloube, F., Charnay, B., Chauvin, G., Chavez, A., Choquet, E., Christiaens, V., Clénet, Y., Foresto, V. Coudé du, Cridland, A., Davies, R., Dembet, R., Dexter, J., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Schreiber, N. M. Förster, Garcia, P., Lopez, R. Garcia, Gardner, T., Gendron, E., Genzel, R., Gillessen, S., Girard, J. H., Grant, S., Haubois, X., Heißel, G., Henning, T., Hinkley, S., Hippler, S., Houllé, M., Hubert, Z., Jocou, L., Kammerer, J., Keppler, M., Kervella, P., Kreidberg, L., Kurtovic, N. T., Lagrange, A. -M., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Lutz, D., Maire, A. -L., Mang, F., Marleau, G. -D., Mérand, A., Monnier, J. D., Mordasini, C., Mouillet, D., Nasedkin, E., Ott, T., Otten, G. P. P. L., Paladini, C., Paumard, T., Perraut, K., Perrin, G., Pfuh, O., Pourré, N., Pueyo, L., Ribeiro, D. C., Rickman, E., Rustamkulov, Z., Shangguan, J., Shimizu, T., Sing, D., Stadler, J., Stolker, T., Straub, O., Straubmeier, C., Sturm, E., Subroweit, M., Tacconi, L. J., van Dishoeck, E. F., Vigan, A., Vincent, F., von Fellenberg, S. D., Wang, J. J., Widmann, F., Winterhalder, T. O., Woillez, J., Yazıcı, Ş., Young, A., and Collaboration, the GRAVITY
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract: Dual-field interferometric observations with VLTI/GRAVITY sometimes require the use of a "binary calibrator", a binary star whose individual components remain unresolved by the interferometer, with a separation between 400 and 2000 mas for observations with the Units Telescopes (UTs), or 1200 to 3000 mas for the Auxiliary Telescopes (ATs). The separation vector also needs to be predictable to within 10 mas for proper pointing of the instrument. Up until now, no list of properly vetted calibrators was available for dual-field observations with VLTI/GRAVITY on the UTs. Our objective is to compile such a list, and make it available to the community. We identify a list of candidates from the Washington Double Star (WDS) catalogue, all with appropriate separations and brightness, scattered over the Southern sky. We observe them as part of a dedicated calibration programme, and determine whether these objects are true binaries (excluding higher multiplicities resolved interferometrically but unseen by imaging), and extract measurements of the separation vectors. We combine these new measurements with those available in the WDS to determine updated orbital parameters for all our vetted calibrators. We compile a list of 13 vetted binary calibrators for observations with VLTI/GRAVITY on the UTs, and provide orbital estimates and astrometric predictions for each of them. We show that our list guarantees that there are always at least two binary calibrators at airmass < 2 in the sky over the Paranal observatory, at any point in time. Any Principal Investigator wishing to use the dual-field mode of VLTI/GRAVITY with the UTs can now refer to this list to select an appropriate calibrator. We encourage the use of "whereistheplanet" to predict the astrometry of these calibrators, which seamlessly integrates with "p2Gravity" for VLTI/GRAVITY dual-field observing material preparation., Comment: 16 pages, 6 figures. Submitted to A&A
Published: 2024
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13. Upgrading the GRAVITY fringe tracker for GRAVITY+: Tracking the white light fringe in the non-observable Optical Path Length state-space

Author: Nowak, M., Lacour, S., Abuter, R., Woillez, J., Dembet, R., Bordoni, M. S., Bourdarot, G., Courtney-Barrer, B., Defrère, D., Drescher, A., Eisenhauer, F., Fabricius, M., Feuchtgruber, H., Frahm, R., Garcia, P., Gillessen, S., Gopinath, V., Graf, J., Hoenig, S., Kreidberg, L., Laugier, R., Bouquin, J. B. Le, Lutz, D., Mang, F., Millour, F., More, N., Morujão, N., Ott, T., Paumard, T., Perrin, G., Rau, C., Ribeiro, D. C., Shangguan, J., Shimizu, T., Soulez, F., Straubmeier, C., Widmann, F., and Wolff, B.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: Aims. As part of the ongoing GRAVITY+ upgrade of the Very Large Telescope Interferometer infrastructure, we aim to improve the performance of the GRAVITY Fringe-Tracker, and to enable its use by other instruments. Methods. We modify the group delay controller to consistently maintain tracking in the white light fringe, characterised by a minimum group delay. Additionally, we introduce a novel approach in which fringe-tracking is performed in the non-observable Optical Path Length state-space, using a covariance-weighted Kalman filter and an auto-regressive model of the disturbance. We outline this new state-space representation, and the formalism we use to propagate the state-vector and generate the control signal. While our approach is presented specifically in the context of GRAVITY/GRAVITY+, it can easily be adapted to other instruments or interferometric facilities. Results. We successfully demonstrate phase delay tracking within a single fringe, with any spurious phase jumps detected and corrected in less than 100 ms. We also report a significant performance improvement, as evidenced by a reduction of about 30 to 40% in phase residuals, and a much better behaviour under sub-optimal atmospheric conditions. Compared to what was observed in 2019, the median residuals have decreased from 150 nm to 100 nm on the Auxiliary Telescopes and from 250 nm to 150 nm on the Unit Telescopes. Conclusions. The improved phase-delay tracking combined with whit light fringe tracking means that from now-on, the GRAVITY Fringe-Tracker can be used by other instruments operating in different wavebands. The only limitation remains the need for an optical path dispersion adjustment., Comment: 16 pages, 8 figures. Accepted for publication in A&A
Published: 2024

14. The GRAVITY young stellar object survey XIII. Tracing the time-variable asymmetric disk structure in the inner AU of the Herbig star HD98922

Author: GRAVITY Collaboration, Ganci, V., Labadie, L., Perraut, K., Wojtczak, A., Kaufhold, J., Benisty, M., Alecian, E., Bourdarot, G., Brandner, W., Garatti, A. Caratti o, Dougados, C., Lopez, R. Garcia, Sanchez-Bermudez, J., Soulain, A., Amorim, A., Berger, J. -P., Caselli, P., Clénet, Y., Drescher, A., Eckart, A., Eisenhauer, F., Fabricius, M., Feuchtgruber, H., Garcia, P., Gendron, E., Genzel, R., Gillessen, S., Grant, S., Heißel, G., Henning, T., Horrobin, M., Jocou, L., Kervella, P., Lacour, S., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Lutz, D., Mang, F., Morujão, N., Ott, T., Paumard, T., Perrin, G., Ribeiro, D., Bordoni, M. Sadun, Scheithauer, S., Shangguan, J., Shimizu, T., Straubmeier, C., Sturm, E., Tacconi, L., van Dishoeck, E., Vincent, F., and Woillez, J.
Subjects: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: Temporal variability in the photometric and spectroscopic properties of protoplanetary disks is common in YSO. However, evidence pointing toward changes in their morphology over short timescales has only been found for a few sources, mainly due to a lack of high cadence observations at mas resolution. We combine GRAVITY multi-epoch observations of HD98922 at mas resolution with PIONIER archival data covering a total time span of 11 years. We interpret the interferometric visibilities and spectral energy distribution with geometrical models and through radiative transfer techniques. We investigated high-spectral-resolution quantities to obtain information on the properties of the HI BrG-line-emitting region. The observations are best fitted by a model of a crescent-like asymmetric dust feature located at 1 au and accounting for 70% of the NIR emission. The feature has an almost constant magnitude and orbits the central star with a possible sub-Keplerian period of 12 months, although a 9 month period is another, albeit less probable, solution. The radiative transfer models show that the emission originates from a small amount of carbon-rich (25%) silicates, or quantum-heated particles located in a low-density region. Among different possible scenarios, we favor hydrodynamical instabilities in the inner disk that can create a large vortex. The high spectral resolution differential phases in the BrG-line show that the hot-gas component is offset from the star and in some cases is located between the star and the crescent feature. The scale of the emission does not favor magnetospheric accretion as a driving mechanism. The scenario of an asymmetric disk wind or a massive accreting substellar or planetary companion is discussed. With this unique observational data set for HD98922, we reveal morphological variability in the innermost 2 au of its disk region., Comment: 45 pages, 20 figures, accepted by and to be published in Astronomy & Astrophysics (A&A)
Published: 2024

15. The GRAVITY young stellar object survey: XI. Imaging the hot gas emission around the Herbig Ae star HD 58647

Author: Bouarour, Y. -I., Lopez, R. Garcia, Sanchez-Bermudez, J., Garatti, A. Caratti o, Perraut, K., Aimar, N., Amorim, A., Berger, J. -P., Bourdarot, G., Brandner, W., Clénet, Y., de Zeeuw, P. T., Dougados, C., Drescher, A., Eckart, A., Eisenhauer, F., Flock, M., Garcia, P., Gendron, E., Genzel, R., Gillessen, S., Grant, S., Heißel, G., Henning, Th., Jocou, L., Kervella, P., Labadie, L., Lacour, S., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Linz, H., Lutz, D., Mang, F., Nowacki, H., Ott, T., Paumard, T., Perrin, G., Pineda, J. E., Ribeiro, D. C., Bordoni, M. Sadun, Shangguan, J., Shimizu, T., Soulain, A., Straubmeier, C., Sturm, E., Tacconi, L., and Vincent, F.
Subjects: Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract: We aim to investigate the origin of the HI Br$\gamma$ emission in young stars by using GRAVITY to image the innermost region of circumstellar disks, where important physical processes such as accretion and winds occur. With high spectral and angular resolution, we focus on studying the continuum and the HI Br$\gamma$-emitting area of the Herbig star HD58647. Using VLTI-GRAVITY, we conducted observations of HD58647 with both high spectral and high angular resolution. Thanks to the extensive $uv$ coverage, we were able to obtain detailed images of the circumstellar environment at a sub-au scale, specifically capturing the continuum and the Br$\gamma$-emitting region. Through the analysis of velocity-dispersed images and photocentre shifts, we were able to investigate the kinematics of the HI Br$\gamma$-emitting region. The recovered continuum images show extended emission where the disk major axis is oriented along a position angle of 14\degr. The size of the continuum emission at 5-sigma levels is $\sim$ 1.5 times more extended than the sizes reported from geometrical fitting (3.69 mas $\pm$ 0.02 mas). This result supports the existence of dust particles close to the stellar surface, screened from the stellar radiation by an optically thick gaseous disk. Moreover, for the first time with GRAVITY, the hot gas component of HD58647 traced by the Br$\gamma$ ,has been imaged. This allowed us to constrain the size of the Br$\gamma$-emitting region and study the kinematics of the hot gas; we find its velocity field to be roughly consistent with gas that obeys Keplerian motion. The velocity-dispersed images show that the size of the hot gas emission is from a more compact region than the continuum (2.3 mas $\pm$ 0.2 mas). Finally, the line phases show that the emission is not entirely consistent with Keplerian rotation, hinting at a more complex structure in the hot gaseous disk., Comment: accepted in A&A on 20/11/2023
Published: 2023

16. VLTI/GRAVITY Provides Evidence the Young, Substellar Companion HD 136164 Ab formed like a 'Failed Star'

Author: Balmer, William O., Pueyo, L., Lacour, S., Wang, J. J., Stolker, T., Kammerer, J., Pourré, N., Nowak, M., Rickman, E., Blunt, S., Sivaramakrishnan, A., Sing, D., Wagner, K., Marleau, G. -D., Lagrange, A. -M., Abuter, R., Amorim, A., Asensio-Torres, R., Berger, J. -P., Beust, H., Boccaletti, A., Bohn, A., Bonnefoy, M., Bonnet, H., Bordoni, M. S., Bourdarot, G., Brandner, W., Cantalloube, F., Caselli, P., Charnay, B., Chauvin, G., Chavez, A., Choquet, E., Christiaens, V., Clénet, Y., Foresto, V. Coudé du, Cridland, A., Davies, R., Dembet, R., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Schreiber, N. M. F"orster, Garcia, P., Lopez, R. Garcia, Gendron, E., Genzel, R., Gillessen, S., Girard, J. H., Grant, S., Haubois, X., Heißel, G., Henning, Th., Hinkley, S., Hippler, S., Houllé, M., Hubert, Z., Jocou, L., Keppler, M., Kervella, P., Kreidberg, L., Kurtovic, N. T., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Lutz, D., Maire, A. -L., Mang, F., Mérand, A., Mollière, P., Mordasini, C., Mouillet, D., Nasedkin, E., Ott, T., Otten, G. P. P. L., Paladini, C., Paumard, T., Perraut, K., Perrin, G., Pfuhl, O., Ribeiro, D. C., Rodet, L., Rustamkulov, Z., Shangguan, J., Shimizu, T., Straubmeier, C., Sturm, E., Tacconi, L. J., Vigan, A., Vincent, F., Ward-Duong, K., Widmann, F., Winterhalder, T., Woillez, J., and Yazici, S.
Subjects: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: Young, low-mass Brown Dwarfs orbiting early-type stars, with low mass ratios ($q\lesssim0.01$), appear intrinsically rare and present a formation dilemma: could a handful of these objects be the highest mass outcomes of ``planetary" formation channels (bottom up within a protoplanetary disk), or are they more representative of the lowest mass ``failed binaries" (formed via disk fragmentation, or core fragmentation)? Additionally, their orbits can yield model-independent dynamical masses, and when paired with wide wavelength coverage and accurate system age estimates, can constrain evolutionary models in a regime where the models have a wide dispersion depending on initial conditions. We present new interferometric observations of the $16\,\mathrm{Myr}$ substellar companion HD~136164~Ab (HIP~75056~Ab) with VLTI/GRAVITY and an updated orbit fit including proper motion measurements from the Hipparcos-Gaia Catalogue of Accelerations. We estimate a dynamical mass of $35\pm10\,\mathrm{M_J}$ ($q\sim0.02$), making HD~136164~Ab the youngest substellar companion with a dynamical mass estimate. The new mass and newly constrained orbital eccentricity ($e=0.44\pm0.03$) and separation ($22.5\pm1\,\mathrm{au}$) could indicate that the companion formed via the low-mass tail of the Initial Mass Function. Our atmospheric fit to the \texttt{SPHINX} M-dwarf model grid suggests a sub-solar C/O ratio of $0.45$, and $3\times$ solar metallicity, which could indicate formation in the circumstellar disk via disk fragmentation. Either way, the revised mass estimate likely excludes ``bottom-up" formation via core accretion in the circumstellar disk. HD~136164~Ab joins a select group of young substellar objects with dynamical mass estimates; epoch astrometry from future \textit{Gaia} data releases will constrain the dynamical mass of this crucial object further., Comment: Accepted for publication in The Astronomical Journal. 9 figures, 3 tables
Published: 2023

17. 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

18. Using the motion of S2 to constrain vector clouds around SgrA*

Author: GRAVITY Collaboration, Foschi, A., Abuter, R., Dayem, K. Abd El, Aimar, N., Seoane, P. Amaro, Amorim, A., Berger, J. P., Bonnet, H., Bourdarot, G., Brandner, W., Davies, R., de Zeeuw, P. T., Defrère, D., Dexter, J., Drescher, A., Eckart, A., Eisenhauer, F., Schreiber, N. M. Förster, Garcia, P. J. V., Genzel, R., Gillessen, S., Gomes, T., Haubois, X., Heißel, G., Henning, Th., Jochum, L., Jocou, L., Kaufer, A., Kreidberg, L., Lacour, S., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Lutz, D., Mang, F., Millour, F., Ott, T., Paumard, T., Perraut, K., Perrin, G., Pfuhl, O., Rabien, S., Ribeiro, D. C., Bordoni, M. Sadun, Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straubmeier, C., Sturm, E., Subroweit, M., Tacconi, L. J., Vincent, F., von Fellenberg, S., and Woillez, J.
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - Instrumentation and Methods for Astrophysics, General Relativity and Quantum Cosmology
Abstract: The dark compact object at the centre of the Milky Way is well established to be a supermassive black hole with mass $M_{\bullet} \sim 4.3 \cdot 10^6 \, M_{\odot}$, but the nature of its environment is still under debate. In this work, we used astrometric and spectroscopic measurements of the motion of the star S2, one of the closest stars to the massive black hole, to determine an upper limit on an extended mass composed of a massive vector field around Sagittarius A*. For a vector with effective mass $10^{-19} \, \rm eV \lesssim m_s \lesssim 10^{-18} \, \rm eV$, our Markov Chain Monte Carlo analysis shows no evidence for such a cloud, placing an upper bound $M_{\rm cloud} \lesssim 0.1\% M_{\bullet}$ at $3\sigma$ confidence level. We show that dynamical friction exerted by the medium on S2 motion plays no role in the analysis performed in this and previous works, and can be neglected thus., Comment: 9 pages, 5 figures, accepted to MNRAS
Published: 2023

19. Polarization analysis of the VLTI and GRAVITY

Author: GRAVITY Collaboration, Widmann, F., Schuhler, X. Haubois N., Pfuhl, O., Eisenhauer, F., Gillessen, S., Aimar, N., Amorim, A., Bauböck, M., Berger, J. B., Bonnet, H., Bourdarot, G., Brandner, W., Clénet, Y., Davies, R., de Zeeuw, P. T., Dexter, J., Drescher, A., Eckart, A., Feuchtgruber, H., Schreiber, N. M. Förster, Garcia, P., Gendron, E., Genzel, R., Hartl, M., Haußmann, F., Heißel, G., Henning, T., Hippler, S., Horrobin, M., Jiménez-Rosales, A., Jocou, L., Kaufer, A., Kervella, P., Lacour, S., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Lutz, D., Mang, F., More, N., Nowak, M., Ott, T., Paumard, T., Perraut, K., Perrin, G., Rabien, S., Ribeiro, D., Bordoni, M. Sadun, Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Tacconi, L. J., Vincent, F., von Fellenberg, S. D., Wieprecht, E., Wiezorrek, E., and Woillez, J.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The goal of this work is to characterize the polarization effects of the VLTI and GRAVITY. This is needed to calibrate polarimetric observations with GRAVITY for instrumental effects and to understand the systematic error introduced to the astrometry due to birefringence when observing targets with a significant intrinsic polarization. By combining a model of the VLTI light path and its mirrors and dedicated experimental data, we construct a full polarization model of the VLTI UTs and the GRAVITY instrument. We first characterize all telescopes together to construct a UT calibration model for polarized targets. We then expand the model to include the differential birefringence. With this, we can constrain the systematic errors for highly polarized targets. Together with this paper, we publish a standalone Python package to calibrate the instrumental effects on polarimetric observations. This enables the community to use GRAVITY to observe targets in a polarimetric observing mode. We demonstrate the calibration model with the galactic center star IRS 16C. For this source, we can constrain the polarization degree to within 0.4 % and the polarization angle within 5 deg while being consistent with the literature. Furthermore, we show that there is no significant contrast loss, even if the science and fringe-tracker targets have significantly different polarization, and we determine that the phase error in such an observation is smaller than 1 deg, corresponding to an astrometric error of 10 {\mu}as. With this work, we enable the use of the polarimetric mode with GRAVITY/UTs and outline the steps necessary to observe and calibrate polarized targets. We demonstrate that it is possible to measure the intrinsic polarization of astrophysical sources with high precision and that polarization effects do not limit astrometric observations of polarized targets., Comment: Accepted by A&A
Published: 2023

20. 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

21. Prospects for $\gamma$-ray observations of the Perseus galaxy cluster with the Cherenkov Telescope Array

Author: Consortium, The Cherenkov Telescope Array, Abe, K., Abe, S., Acero, F., Acharyya, A., Adam, R., Aguasca-Cabot, A., Agudo, I., Aguirre-Santaella, A., Alfaro, J., Alfaro, R., Alvarez-Crespo, N., Batista, R. Alves, Amans, J. -P., Amato, E., Angüner, E. O., Antonelli, L. A., Aramo, C., Araya, M., Arcaro, C., Arrabito, L., Asano, K., Ascasíbar, Y., Aschersleben, J., Ashkar, H., Stuani, L. Augusto, Baack, D., Backes, M., Baktash, A., Balazs, C., Balbo, M., Ballester, O., Larriva, A. Baquero, Martins, V. Barbosa, de Almeida, U. Barres, Barrio, J. A., Batista, P. I., Batkovic, I., Batzofin, R., Baxter, J., González, J. Becerra, Beck, G., Tjus, J. Becker, Benbow, W., Medrano, J. Bernete, Bernlöhr, K., Berti, A., Bertucci, B., Beshley, V., Bhattacharjee, P., Bhattacharyya, S., Bi, B., Biederbeck, N., Biland, A., Bissaldi, E., Biteau, J., Blanch, O., Blazek, J., Boisson, C., Bolmont, J., Bordas, P., Bosnjak, Z., Bottacini, E., Bradascio, F., Braiding, C., Bronzini, E., Brose, R., Brown, A. M., Brun, F., Brunetti, G., Bucciantini, N., Bulgarelli, A., Burelli, I., Burmistrov, L., Burton, M., Bylund, T., Calisse, P. G., Campoy-Ordaz, A., Cantlay, B. K., Capalbi, M., Caproni, A., Capuzzo-Dolcetta, R., Caraveo, P., Caroff, S., Carosi, R., Carquin, E., Carrasco, M. -S., Cascone, E., Cassol, F., Castro-Tirado, A. J., Cerasole, D., Cerruti, M., Chadwick, P., Chaty, S., Chen, A. W., Chernyakova, M., Chiavassa, A., Chudoba, J., Chytka, L., Cifuentes, A., Araujo, C. H. Coimbra, Conforti, V., Conte, F., Contreras, J. L., Cortina, J., Costa, A., Costantini, H., Cotter, G., Cristofari, P., Cuevas, O., Curtis-Ginsberg, Z., D'Amico, G., D'Ammando, F., Dalchenko, M., Dazzi, F., de Lavergne, M. de Bony, De Caprio, V., Laadim, F. De Frondat, Pino, E. M. de Gouveia Dal, De Lotto, B., De Lucia, M., De Martino, D., de Menezes, R., de Naurois, M., De Simone, N., de Souza, V., del Valle, M. V., Delagnes, E., Giler, A. G. Delgado, Delgado, C., Dell'aiera, M., della Volpe, D., Depaoli, D., Di Girolamo, T., Di Piano, A., Di Pierro, F., Di Tria, R., Di Venere, L., Diebold, S., Djannati-Ataï, A., Djuvsland, J., Dominik, R. M., Donini, A., Dorner, D., Dörner, J., Doro, M., Anjos, R. D. C. dos, Dournaux, J. -L., Duangchan, C., Dubos, C., Dumora, D., Dwarkadas, V. V., Ebr, J., Eckner, C., Egberts, K., Einecke, S., Elsässer, D., Emery, G., Godoy, M. Escobar, Escudero, J., Esposito, P., Ettori, S., Evoli, C., Falceta-Goncalves, D., Ramazani, V. Fallah, Fattorini, A., Faure, A., Fedorova, E., Fegan, S., Feijen, K., Feng, Q., Ferrand, G., Ferrarotto, F., Fiandrini, E., Fiasson, A., Filipovic, M., Fioretti, V., Foffano, L., Guiteras, L. Font, Fontaine, G., Fröse, S., Fukazawa, Y., Fukui, Y., Gaggero, D., Galanti, G., Gallozzi, S., Gammaldi, V., Garczarczyk, M., Gasbarra, C., Gasparrini, D., Gaug, M., Ghalumyan, A., Gianotti, F., Giarrusso, M., Giesbrecht, J., Giglietto, N., Giordano, F., Glicenstein, J. -F., Göksu, H., Goldoni, P., González, J. M., González, M. M., Coelho, J. Goulart, Granot, J., Grau, R., Gréaux, L., Green, D., Green, J. G., Grenier, I., Grolleron, G., Grube, J., Gueta, O., Hackfeld, J., Hadasch, D., Hamal, P., Hanlon, W., Hara, S., Harvey, V. M., Hassan, T., Heckmann, L., Heller, M., Cadena, S. Hernández, Hervet, O., Hie, J., Hiroshima, N., Hnatyk, B., Hnatyk, R., Hoang, J., Hoffmann, D., Hofmann, W., Holder, J., Horan, D., Horvath, P., Hrupec122, D., Hütten, M., Iarlori, M., Inada, T., Incardona, F., Inoue, S., Iocco, F., Iori, M., Jamrozy, M., Janecek, P., Jankowsky, F., Jarnot, C., Jean, P., Martínez, I. Jiménez, Jin, W., Juramy-Gilles, C., Jurysek, J., Kagaya, M., Kantzas, D., Karas, V., Katagiri, H., Kataoka, J., Kaufmann, S., Kerszberg, D., Khélifi, B., Kissmann, R., Kleiner, T., Kluge, G., Kluźniak, W., Knödlseder, J., Kobayashi, Y., Kohri, K., Komin, N., Kornecki, P., Kosack, K., Kowal, G., Kubo, H., Kushida, J., La Barbera, A., La Palombara, N., Láinez, M., Lamastra, A., Lapington, J., Laporte, P., Lazarević, S., Leitgeb, F., Lemoine-Goumard, M., Lenain, J. -P., Leone, F., Leto, G., Leuschner, F., Lindfors, E., Linhoff, M., Liodakis, I., Lombardi, S., Longo, F., López-Coto, R., López-Moya, M., López-Oramas, A., Loporchio, S., Luque-Escamilla, P. L., Macias, O., Mackey, J., Majumdar, P., Malyshev, D., Mandat, D., Manganaro, M., Manicò, G., Mariotti, M., Markoff, S., Márquez, I., Marquez, P., Marsella, G., Martínez, G. A., Martínez, M., Martinez, O., Marty, C., Mas-Aguilar, A., Mastropietro, M., Maurin, G., Mazin, D., Melkumyan, D., Mello, A. J. T. S., Meunier, J. -L., Meyer, D. M. -A., Meyer, M., Miceli, D., Michailidis, M., Michałowski, J., Miener, T., Miranda, J. M., Mitchell, A., Mizote, M., Mizuno, T., Moderski, R., Molero, M., Molfese, C., Molina, E., Montaruli, T., Morcuende, D., Morik, K., Morlino, G., Morselli, A., Moulin, E., Zamanillo, V. Moya, Munari, K., Murach, T., Muraczewski, A., Muraishi, H., Nagataki, S., Nakamori, T., Nemmen, R., Neyroud, N., Nickel, L., Niemiec, J., Nieto, D., Rosillo, M. Nievas, Nikołajuk, M., Nishijima, K., Noda, K., Nosek, D., Novotny, V., Nozaki, S., O'Brien, P., Ohishi, M., Ohtani, Y., Okumura, A., Olive, J. -F., Olmi, B., Ong, R. A., Orienti, M., Orito, R., Orlandini, M., Orlando, E., Ostrowski, M., Oya, I., Pagliaro, A., Palatiello, M., Panebianco, G., Paneque, D., Pantaleo, F. R., Paoletti, R., Paredes, J. M., Parmiggiani, N., Patel, S. R., Patricelli, B., Pavlović, D., Pech, M., Pecimotika, M., Pensec, U., Peresano, M., Pérez-Romero, J., Peron, G., Persic, M., Petrucci, P. -O., Petruk, O., Piano, G., Pierre, E., Pietropaolo, E., Pintore, F., Pirola, G., Pita, S., Plard, C., Podobnik, F., Pohl, M., Polo, M., Pons, E., Ponti, G., Prandini, E., Prast, J., Principe, G., Priyadarshi, C., Produit, N., Pueschel, E., Pühlhofer, G., Pumo, M. L., Punch, M., Queiroz, F., Quirrenbach, A., Rainò, S., Rando, R., Razzaque, S., Recchia, S., Regeard, M., Reichherzer, P., Reimer, A., Reimer, O., Reisenegger, A., Rhode, W., Ribeiro, D., Ribó, M., Richtler, T., Rico, J., Rieger, F., Righi, C., Riitano, L., Rizi, V., Roache, E., Fernandez, G. Rodriguez, Rodríguez-Vázquez, J. J., Romano, P., Romeo, G., Rosado, J., de Leon, A. Rosales, Rowell, G., Rudak, B., Rulten, C. B., Russo, F., Sadeh, I., Saha, L., Saito, T., Salzmann, H., Sanchez, D., Sánchez-Conde, M., Sangiorgi, P., Sano, H., Santander, M., Santangelo, A., Santos-Lima, R., Sanuy, A., Šarić, T., Sarkar, A., Sarkar, S., Satalecka, K., Saturni, F. G., Savchenko, V., Scherer, A., Schipani, P., Schleicher, B., Schubert, J. L., Schussler, F., Schwanke, U., Schwefer, G., Arroyo, M. Seglar, Seiji, S., Semikoz, D., Sergijenko, O., Servillat, M., Sguera, V., Shang, R. Y., Sharma, P., Siejkowski, H., Sinha, A., Siqueira, C., Sliusar, V., Slowikowska, A., Sol, H., Specovius, A., Spencer, S. T., Spiga, D., Stamerra, A., Stanič, S., Starecki, T., Starling, R., Stawarz, Ł., Steppa, C., Stolarczyk, T., Strišković, J., Suda, Y., Suomijärvi, T., Tajima, H., Tak, D., Takahashi, M., Takeishi, R., Tanaka, S. J., Tavernier, T., Tejedor, L. A., Terauchi, K., Terrier, R., Teshima, M., Tian, W. W., Tibaldo, L., Tibolla, O., Torradeflot, F., Torres, D. F., Torresi, E., Tosti, G., Tosti, L., Tothill, N., Toussenel, F., Touzard, V., Tramacere, A., Travnicek, P., Tripodo, G., Truzzi, S., Tsiahina, A., Tutone, A., Vacula, M., Vallage, B., Vallania, P., van Eldik, C., van Scherpenberg, J., Vandenbroucke, J., Vassiliev, V., Acosta, M. Vázquez, Vecchi, M., Ventura, S., Vercellone, S., Verna, G., Viana, A., Viaux, N., Vigliano, A., Vigorito, C. F., Vitale, V., Vodeb, V., Voisin, V., Vorobiov, S., Voutsinas, G., Vovk, I., Vuillaume, T., Wagner, S. J., Walter, R., Wechakama, M., White, R., Wierzcholska, A., Will, M., Williams, D. A., Wohlleben, F., Wolter, A., Yamamoto, T., Yamazaki, R., Yoshida, T., Yoshikoshi, T., Zacharias, M., Zaharijas, G., Zavrtanik, D., Zavrtanik, M., Zdziarski, A. A., Zech, A., Zhdanov, V. I., Živec, M., Zuriaga-Puig, J., and Luque, P. De la Torre
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics, High Energy Physics - Phenomenology
Abstract: Galaxy clusters are expected to be dark matter (DM) reservoirs and storage rooms for the cosmic-ray protons (CRp) that accumulate along the cluster's formation history. Accordingly, they are excellent targets to search for signals of DM annihilation and decay at gamma-ray energies and are predicted to be sources of large-scale gamma-ray emission due to hadronic interactions in the intracluster medium. We estimate the sensitivity of the Cherenkov Telescope Array (CTA) to detect diffuse gamma-ray emission from the Perseus galaxy cluster. We perform a detailed spatial and spectral modelling of the expected signal for the DM and the CRp components. For each, we compute the expected CTA sensitivity. The observing strategy of Perseus is also discussed. In the absence of a diffuse signal (non-detection), CTA should constrain the CRp to thermal energy ratio within the radius $R_{500}$ down to about $X_{500}<3\times 10^{-3}$, for a spatial CRp distribution that follows the thermal gas and a CRp spectral index $\alpha_{\rm CRp}=2.3$. Under the optimistic assumption of a pure hadronic origin of the Perseus radio mini-halo and depending on the assumed magnetic field profile, CTA should measure $\alpha_{\rm CRp}$ down to about $\Delta\alpha_{\rm CRp}\simeq 0.1$ and the CRp spatial distribution with 10% precision. Regarding DM, CTA should improve the current ground-based gamma-ray DM limits from clusters observations on the velocity-averaged annihilation cross-section by a factor of up to $\sim 5$, depending on the modelling of DM halo substructure. In the case of decay of DM particles, CTA will explore a new region of the parameter space, reaching models with $\tau_{\chi}>10^{27}$s for DM masses above 1 TeV. These constraints will provide unprecedented sensitivity to the physics of both CRp acceleration and transport at cluster scale and to TeV DM particle models, especially in the decay scenario., Comment: 93 pages (including author list, appendix and references), 143 figures. Submitted to JCAP
Published: 2023
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22. Polarimetry and Astrometry of NIR Flares as Event Horizon Scale, Dynamical Probes for the Mass of Sgr A*

Author: The GRAVITY Collaboration, Abuter, R., Aimar, N., Seoane, P. Amaro, Amorim, A., Bauböck, M., Berger, J. P., Bonnet, H., Bourdarot, G., Brandner, W., Cardoso, V., Clénet, Y., Davies, R., de Zeeuw, P. T., Dexter, J., Drescher, A., Eckart, A., Eisenhauer, F., Feuchtgruber, H., Finger, G., Schreiber, N. M. Förster, Foschi, A., Garcia, P., Gao, F., Gelles, Z., Gendron, E., Genzel, R., Gillessen, S., Hartl, M., Haubois, X., Haussmann, F., Heißel, G., Henning, T., Hippler, S., Horrobin, M., Jochum, L., Jocou, L., Kaufer, A., Kervella, P., Lacour, S., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Lutz, D., Mang, F., More, N., Ott, T., Paumard, T., Perraut, K., Perrin, G., Pfuhl, O., Rabien, S., Ribeiro, D. C., Bordoni, M. Sadun, Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Tacconi, L. J., Vincent, F., von Fellenberg, S., Widmann, F., Wielgus, M., Wieprecht, E., Wiezorrek, E., and Woillez, J.
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Abstract: We present new astrometric and polarimetric observations of flares from Sgr A* obtained with GRAVITY, the near-infrared interferometer at ESO's Very Large Telescope Interferometer (VLTI), bringing the total sample of well-covered astrometric flares to four and polarimetric ones to six, where we have for two flares good coverage in both domains. All astrometric flares show clockwise motion in the plane of the sky with a period of around an hour, and the polarization vector rotates by one full loop in the same time. Given the apparent similarities of the flares, we present a common fit, taking into account the absence of strong Doppler boosting peaks in the light curves and the EHT-measured geometry. Our results are consistent with and significantly strengthen our model from 2018: We find that a) the combination of polarization period and measured flare radius of around nine gravitational radii ($9 R_g \approx 1.5 R_{ISCO}$, innermost stable circular orbit) is consistent with Keplerian orbital motion of hot spots in the innermost accretion zone. The mass inside the flares' radius is consistent with the $4.297 \times 10^6 \; \text{M}_\odot$ measured from stellar orbits at several thousand $R_g$. This finding and the diameter of the millimeter shadow of Sgr A* thus support a single black hole model. Further, b) the magnetic field configuration is predominantly poloidal (vertical), and the flares' orbital plane has a moderate inclination with respect to the plane of the sky, as shown by the non-detection of Doppler-boosting and the fact that we observe one polarization loop per astrometric loop. Moreover, c) both the position angle on sky and the required magnetic field strength suggest that the accretion flow is fueled and controlled by the winds of the massive, young stars of the clockwise stellar disk 1-5 arcsec from Sgr A*, in agreement with recent simulations., Comment: 10 pages, 12 figures. Accepted for publication in A&A
Published: 2023
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23. 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

24. Using the motion of S2 to constrain scalar clouds around SgrA*

Author: GRAVITY Collaboration, Foschi, A., Abuter, R., Aimar, N., Seoane, P. Amaro, Amorim, A., Bauböck, M., Berger, J. P., Bonnet, H., Bourdarot, G., Brandner, W., Cardoso, V., Clénet, Y., Dallilar, Y., Davies, R., de Zeeuw, P. T., Defrère, D., Dexter, J., Drescher, A., Eckart, A., Eisenhauer, F., Ferreira, M. C., Schreiber, N. M. Förster, Garcia, P. J. V., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Gomes, T., Habibi, M., Haubois, X., Heißel, G., Henning, T., Hippler, S., Hönig, S. F., Horrobin, M., Jochum, L., Jocou, L., Kaufer, A., Kervella, P., Kreidberg, L., Lacour, S., Lapeyrère, V., Bouquin, J. B. Le, Léna, P., Lutz, D., Millour, F., Ott, T., Paumard, T., Perraut, K., Perrin, G., Pfuhl, O., Rabien, S., Ribeiro, D. C., Bordoni, M. Sadun, Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Sykes, C., Tacconi, L. J., Vincent, F., von Fellenberg, S., Widmann, F., Wieprecht, E., Wiezorrek, E., and Woillez, J.
Subjects: Astrophysics - Astrophysics of Galaxies, Astrophysics - Instrumentation and Methods for Astrophysics, General Relativity and Quantum Cosmology
Abstract: The motion of S2, one of the stars closest to the Galactic Centre, has been measured accurately and used to study the compact object at the centre of the Milky Way. It is commonly accepted that this object is a supermassive black hole but the nature of its environment is open to discussion. Here, we investigate the possibility that dark matter in the form of an ultralight scalar field ``cloud'' clusters around Sgr~A*. We use the available data for S2 to perform a Markov Chain Monte Carlo analysis and find the best-fit estimates for a scalar cloud structure. Our results show no substantial evidence for such structures. When the cloud size is of the order of the size of the orbit of S2, we are able to constrain its mass to be smaller than $0.1\%$ of the central mass, setting a strong bound on the presence of new fields in the galactic centre., Comment: Published on MNRAS. References added
Published: 2023
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25. Where intermediate-mass black holes could hide in the Galactic Centre: A full parameter study with the S2 orbit

Author: The GRAVITY Collaboration, Straub, O., Bauböck, M., Abuter, R., Aimar, N., Seoane, P. Amaro, Amorim, A., Berger, J. P., Bonnet, H., Bourdarot, G., Brandner, W., Cardoso, V., Clénet, Y., Dallilar, Y., Davies, R., de Zeeuw, P. T., Dexter, J., Drescher, A., Eisenhauer, F., Schreiber, N. M. Förster, Foschi, A., Garcia, P., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Habibi, M., Haubois, X., Heißel, G., Henning, T., Hippler, S., Horrobin, M., Jochum, L., Jocou, L., Kaufer, A., Kervella, P., Lacour, S., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Lutz, D., Ott, T., Paumard, T., Perraut, K., Perrin, G., Pfuhl, O., Rabien, S., Ribeiro, D. C., Bordoni, M. Sadun, Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straubmeier, C., Sturm, E., Tacconi, L. J., Vincent, F., von Fellenberg, S., Widmann, F., Wieprecht, E., Wiezorrek, E., and Woillez, J.
Subjects: Astrophysics - Astrophysics of Galaxies
Abstract: In the Milky Way the central massive black hole, SgrA*, coexists with a compact nuclear star cluster that contains a sub-parsec concentration of fast-moving young stars called S-stars. Their location and age are not easily explained by current star formation models, and in several scenarios the presence of an intermediate-mass black hole (IMBH) has been invoked. We use GRAVITY astrometric and SINFONI, KECK, and GNIRS spectroscopic data of S2 to investigate whether a second massive object could be present deep in the Galactic Centre (GC) in the form of an IMBH binary companion to SgrA*. To solve the three-body problem, we used a post-Newtonian framework and consider two types of settings: (i) a hierarchical set-up where the star S2 orbits the SgrA* - IMBH binary and (ii) a non-hierarchical set-up where the IMBH trajectory lies outside the S2 orbit. In both cases we explore the full 20-dimensional parameter space by employing a Bayesian dynamic nested sampling method. For the hierarchical case we find: IMBH masses > 2000 Msun on orbits with smaller semi-major axes than S2 are largely excluded. For the non-hierarchical case the parameter space contains several pockets of valid IMBH solutions. However, a closer analysis of their impact on the resident stars reveals that IMBHs on semi-major axes larger than S2 tend to disrupt the S-star cluster in less than a million years. This makes the existence of an IMBH among the S-stars highly unlikely. The current S2 data do not formally require the presence of an IMBH. If an IMBH hides in the GC, it has to be either a low-mass IMBH inside the S2 orbit that moves on a short and significantly inclined trajectory or an IMBH with a semi-major axis >1". We provide the parameter maps of valid IMBH solutions in the GC and discuss the general structure of our results. (abridged), Comment: 11 pages, 6 figures, published in A $\&$ A
Published: 2023
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26. 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
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27. 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
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28. 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
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29. 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
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30. 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
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31. Prototype Schwarzschild-Couder Telescope for the Cherenkov Telescope Array: Commissioning the Optical System

Author: Adams, C. B., Ambrosi, G., Ambrosio, M., Aramo, C., Batista, P. I., Benbow, W., Bertucci, B., Bissaldi, E., Bitossi, M., Boiano, A., Bonavolontà, C., Bose, R., Brill, A., Buckley, J. H., Cameron, R. A., Canestrari, R., Capasso, M., Caprai, M., Covault, C. E., Depaoli, D., Di Venere, L., Errando, M., Fegan, S., Feng, Q., Fiandrini, E., Furniss, A., Gent, A., Giglietto, N., Giordano, F., Giro, E., Halliday, R., Hervet, O., Humensky, T. B., Incardona, S., Ionica, M., Jin, W., Kieda, D., Licciulli, F., Loporchio, S., Marsella, G., Masone, V., Meagher, K., Meures, T., Mode, B. A. W., Mognet, S. A. I., Mukherjee, R., Nieto, D., Okumura, A., Otte, N., Pantaleo, F. R., Paoletti, R., Pareschi, G., Di Pierro, F., Pueschel, E., Ribeiro, D., Riitano, L., Roache, E., Rousselle, J., Rugliancich, A., Santander, M., Shang, R., Stiaccini, L., Taylor, L. P., Tosti, L., Tovmassian, G., Tripodo, G., Vagelli, V., Valentino, M., Vandenbroucke, J., Vassiliev, V. V., Williams, D. A., and Yu, P.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Physics - Optics
Abstract: A prototype Schwarzschild-Couder Telescope (pSCT) has been constructed at the Fred Lawrence Whipple Observatory as a candidate for the medium-sized telescopes of the Cherenkov Telescope Array Observatory (CTAO). CTAO is currently entering early construction phase of the project and once completed it will vastly improve very high energy gamma-ray detection component in multi-wavelength and multi-messenger observations due to significantly improved sensitivity, angular resolution and field of view comparing to the current generation of the ground-based gamma-ray observatories H.E.S.S., MAGIC and VERITAS. The pSCT uses a dual aspheric mirror design with a $9.7$ m primary mirror and $5.4$ m secondary mirror, both of which are segmented. The Schwarzschild-Couder (SC) optical system (OS) selected for the prototype telescope achieves wide field of view of $8$ degrees and simultaneously reduces the focal plane plate scale allowing an unprecedented compact ($0.78$m diameter) implementation of the high-resolution camera ($6$mm/ $0.067$deg per imaging pixel with $11,328$ pixels) based on the silicon photo-multipliers (SiPMs). The OS of the telescope is designed to eliminate spherical and comatic aberrations and minimize astigmatism to radically improve off-axis imaging and consequently angular resolution across all the field of view with respect to the conventional single-mirror telescopes. Fast and high imaging resolution OS of the pSCT comes with the challenging submillimeter-precision custom alignment system, which was successfully demonstrated with an on-axis point spread function (PSF) of $2.9$ arcmin prior to the first-light detection of the Crab Nebula in 2020. Ongoing and future commissioning activities are reported.
Published: 2021

32. 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
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33. 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
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34. Detection of the Crab Nebula by the prototype Schwarzschild-Couder Telescope

Author: Adams, C. B., Ambrosi, G., Ambrosio, M., Aramo, C., Batista, P. I., Benbow, W., Bertucci, B., Bissaldi, E., Bitossi, M., Boiano, A., Bonavolontà, C., Bose, R., Brill, A., Brown, A. M., Buckley, J. H., Cameron, R. A., Canestrari, R., Capasso, M., Caprai, M., Covault, C. E., Depaoli, D., Di Venere, L., Errando, M., Fegan, S., Feng, Q., Fiandrini, E., Furniss, A., Gent, A., Giglietto, N., Giordano, F., Giro, E., Halliday, R., Hervet, O., Holder, J., Humensky, T. B., Incardona, S., Ionica, M., Jin, W., Kieda, D., Licciulli, F., Loporchio, S., Marsella, G., Masone, V., Meagher, K., Meures, T., Mode, B. A. W., Mognet, S. A. I., Mukherjee, R., Okumura, A., Otte, N., Pantaleo, F. R., Paoletti, R., Pareschi, G., Di Pierro, F., Pueschel, E., Ribeiro, D., Riitano, L., Roache, E., Rousselle, J., Rugliancich, A., Santander, M., Shang, R., Stiaccini, L., Tajima, H., Taylor, L. P., Tosti, L., Tovmassian, G., Tripodo, G., Vagelli, V., Valentino, M., Vandenbroucke, J., Vassiliev, V. V., Williams, D. A., and Zink, A.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Schwarzschild-Couder Telescope (SCT) is a medium-sized telescope technology proposed for the Cherenkov Telescope Array. It uses a novel dual-mirror optical design that removes comatic aberrations across its entire field of view. The SCT camera employs high-resolution silicon photomultiplier (SiPM) sensors with a pixel size of 4 arcminutes. A prototype SCT (pSCT) has been constructed at the Fred Lawrence Whipple Observatory in Arizona, USA. An observing campaign in 2020, with a partial camera of 1600 pixels (2.7 degrees by 2.7 degrees field of view) resulted in detection of the Crab Nebula at 8.6 sigma statistical significance. Work on the pSCT camera and optical system is ongoing to improve performance and prepare for an upcoming camera upgrade. The pSCT camera upgrade will replace the current camera modules with improved SiPMs and readout electronics and will expand the camera to its full design field of view of 8 degrees in diameter (11,328 pixels). The fully upgraded pSCT will enable next-generation very-high-energy gamma-ray astrophysics through excellent background rejection and angular resolution. In this presentation we describe first results from the successful operation of the pSCT and future plans., Comment: 9 pages, 3 figures, 2 tables, contribution to ICRC 2021, similar to 10.1016/j.astropartphys.2021.102562 (arXiv:2012.08448)
Published: 2021
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35. Design and performance of the prototype Schwarzschild-Couder Telescope camera

Author: Adams, C. B., Ambrosi, G., Ambrosio, M., Aramo, C., Batista, P. I., Benbow, W., Bertucci, B., Bissaldi, E., Bitossi, M., Boiano, A., Bonavolonta, C., Bose, R., Brill, A., Brown, A. M., Buckley, J. H., Cameron, R. A., Capasso, M., Caprai, M., Covault, C. E., Depaoli, D., Di Venere, L., Errando, M., Fegan, S., Feng, Q., Fiandrini, E., Furniss, A., Gent, A., Giglietto, N., Giordano, F., Halliday, R., Hervet, O., Humensky, T. B., Incardona, S., Ionica, M., Jin, W., Kieda, D., Licciulli, F., Loporchio, S., Marsella, G., Masone, V., Meagher, K., Meures, T., Mode, B. A. W., Mognet, S. A. I., Mukherjee, R., Okumura, A., Otte, N., Pantaleo, F. R., Paoletti, R., Pareschi, G., Di Pierro, F., Pueschel, E., Ribeiro, D., Riitano, L., Roache, E., Ross, D., Rousselle, J., Rugliancich, A., Santander, M., Shang, R., Stiaccini, L., Tajima, H., Taylor, L. P., Tosti, L., Tovmassian, G., Tripodo, G., Vagelli, V., Valentino, M., Vandenbroucke, J., Vassiliev, V. V., Watson, J. J., White, R., Williams, D. A., and Zink, A.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: The Cherenkov Telescope Array (CTA) is the next-generation ground-based observatory for very-high-energy gamma-ray astronomy. An innovative 9.7 m aperture, dual-mirror Schwarzschild-Couder Telescope (SCT) design is a candidate design for CTA Medium-Sized Telescopes. A prototype SCT (pSCT) has been constructed at the Fred Lawrence Whipple Observatory in Arizona, USA. Its camera is currently partially instrumented with 1600 pixels covering a field of view of 2.7 degrees square. The small plate scale of the optical system allows densely packed silicon photomultipliers to be used, which combined with high-density trigger and waveform readout electronics enable the high-resolution camera. The camera's electronics are capable of imaging air shower development at a rate of one billion samples per second. We describe the commissioning and performance of the pSCT camera, including trigger and waveform readout performance, calibration, and absolute GPS time stamping. We also present the upgrade to the camera, which is currently underway. The upgrade will fully populate the focal plane, increasing the field of view to 8 degree diameter, and lower the front-end electronics noise, enabling a lower trigger threshold and improved reconstruction and background rejection., Comment: 8 pages, 5 figures, Proceedings of the 37th International Cosmic Ray Conference (ICRC 2021), Berlin, Germany
Published: 2021
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36. 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

37. 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
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38. A Search for TeV Gamma-ray Emission from Pulsar Tails by VERITAS

Author: Benbow, Wystan, Brill, A., Buckley, James, Capasso, M, Chromey, A, Errando, M., Falcone, Abraham, Farrell, K. A., Feng, Qi, Finley, J, Foote, G. M., Fortson, Lucy, Furniss, Amy, Gent, Alasdair, Giuri, C, Hanna, David, Hassan, Tarek, Hervet, Olivier, Holder, Jamie, Hughes, G, Humensky, T. B., Jin, Weidong, Kaaret, Philip, Kargaltsev, Oleg, Kertzman, Mary P., Kieda, David, Klingler, Noel, Kumar, Sajan, Lang, M, Lundy, M, Maier, Gernot, McGrath, C. E., Moriarty, Patrick, Mukherjee, Reshmi, Nieto, D, Nievas-Rosillo, M, O'Brien, S, Ong, Rene A., Otte, A. N., Patel, S., Pfrang, Konstantin, Pohl, Martin, Prado, Raul, Quinn, John, Ragan, Kenneth J., Reynolds, T., Ribeiro, D, Richards, G. T., Roache, Emmet Thomas, Ryan, James, Santander, Marcos, Sembroski, Glenn H, Shang, R, Volkov, Igor, Wakely, S. P, Weinstein, Amanda, Wilcox, P., and Williams, D. A.
Subjects: Astrophysics - High Energy Astrophysical Phenomena
Abstract: We report on the search for very-high-energy gamma-ray emission from the regions around three nearby supersonic pulsars (PSR B0355+54, PSR J0357+3205 and PSR J1740+1000) that exhibit long X-ray tails. To date there is no clear detection of TeV emission from any pulsar tail that is prominent in X-ray or radio. We provide upper limits on the TeV flux, and luminosity, and also compare these limits with other pulsar wind nebulae detected in X-rays and the tail emission model predictions. We find that at least one of the three tails is likely to be detected in observations that are a factor of 2-3 more sensitive. The analysis presented here also has implications for deriving the properties of pulsar tails, for those pulsars whose tails could be detected in TeV., Comment: 21 pages, 6 figures
Published: 2021
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39. 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
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40. How data curation and new geographical records can change the conservation status of threatened brazilian butterflies

Author: Rosa, Augusto H. B., Ribeiro, D. B., and Freitas, André V. L.
Published: 2023
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41. Detection of the Crab Nebula with the 9.7 m Prototype Schwarzschild-Couder Telescope

Author: Adams, C. B., Alfaro, R., Ambrosi, G., Ambrosio, M., Aramo, C., Arlen, T., Batista, P. I., Benbow, W., Bertucci, B., Bissaldi, E., Biteau, J., Bitossi, M., Boiano, A., Bonavolontà, C., Bose, R., Bouvier, A., Brill, A., Brown, A. M., Buckley, J. H., Byrum, K., Cameron, R. A., Canestrari, R., Capasso, M., Caprai, M., Covault, C. E., Depaoli, D., Errando, M., Fegan, S., Feng, Q., Fiandrini, E., Foote, G., Fortin, P., Funk, S., Furniss, A., Garfias, F., Gent, A., Giglietto, N., Giordano, F., Giro, E., González, M. M., Guarino, V., Halliday, R., Hervet, O., Holder, J., Hughes, G., Humensky, T. B., Ionica, M., Iriarte, A., Jin, W., Johnson, C. A., Kaaret, P., Kieda, D., Kim, B., Kuznetsov, A., Lapington, J. S., Licciulli, F., Loporchio, S., Mason, V., Meagher, K., Meures, T., Mode, B. A. W., Mognet, S. A. I., Mukherjee, R., Nguyen, T., Nieto, D., Okumura, A., Otte, N., La Palombara, N., Pantaleo, F. R., Paoletti, R., Pareschi, G., Petrashyk, A., Di Pierro, F., Pueschel, E., Reynolds, P. T., Ribeiro, D., Richards, G., Roache, E., Ross, D., Rousselle, J., Rugliancich, A., Ruíz-Díaz-Soto, J., Santander, M., Schlenstedt, S., Schneider, M., Scuderi, S., Shang, R., Sironi, G., Stevenson, B., Stiaccini, L., Tajima, H., Taylor, L. P., Thornhill, J., Tosti, L., Tovmassian, G., Vagelli, V., Valentino, M., Vandenbroucke, J., Vassiliev, V. V., Di Venere, L., Wakely, S. P., Watson, J. J., White, R., Wilcox, P., Williams, D. A., Wood, M., Yu, P., and Zink, A.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Schwarzschild-Couder Telescope (SCT) is a telescope concept proposed for the Cherenkov Telescope Array. It employs a dual-mirror optical design to remove comatic aberrations over an $8^{\circ}$ field of view, and a high-density silicon photomultiplier camera (with a pixel resolution of 4 arcmin) to record Cherenkov emission from cosmic ray and gamma-ray initiated particle cascades in the atmosphere. The prototype SCT (pSCT), comprising a 9.7 m diameter primary mirror and a partially instrumented camera with 1536 pixels, has been constructed at the Fred Lawrence Whipple Observatory. The telescope was inaugurated in January 2019, with commissioning continuing throughout 2019. We describe the first campaign of observations with the pSCT, conducted in January and February of 2020, and demonstrate the detection of gamma-ray emission from the Crab Nebula with a statistical significance of $8.6\sigma$., Comment: 13 pages, 12 figures, 3 tables, submitted to Astroparticle Physics
Published: 2020
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42. Verification of the Optical System of the 9.7-m Prototype Schwarzschild-Couder Telescope

Author: Adams, C., Alfaro, R., Ambrosi, G., Ambrosio, M., Aramo, C., Benbow, W., Bertucci, B., Bissaldi, E., Bitossi, M., Boiano, A., Bonavolontà, C., Bose, R., Brill, A., Buckley, J. H., Byrum, K., Cameron, R. A., Capasso, M., Caprai, M., Covault, C. E., Di Venere, L., Fegan, S., Feng, Q., Fiandrini, E., Furniss, A., Garczarczyk, M., Garfias, F., Gent, A., Giglietto, N., Giordano, F., González, M. M., Halliday, R., Hervet, O., Hughes, G., Humensky, T. B., Ionica, M., Iriarte, A., Jin, W., Kaarat, P., Kieda, D., Kim, B., Licciulli, F., Limon, M., Loporchio, S., Masone, V., Meures, T., Mode, B. A. W., Mukherjee, R., Nieto, D., Okumura, A., Otte, N., La Palombara, N., Pantaleo, F. R., Paoletti, R., Pareschi, G., Petrashyk, A., Powell, J., Powell, K., Ribeiro, D., Roache, E., Rousselle, J., Rugliancich, A., Ruíz-Díaz-Soto, J., Santander, M., Schlenstedt, S., Scuderi, S., Shang, R., Sironi, G., Stevenson, B., Stiaccini, L., Taylor, L. P., Tosti, L., Tovmassian, G., Vagelli, V., Valentino, M., Vandenbroucke, J., Vassiliev, V. V., Wakely, S. P., Wilcox, P., Williams, D. A., and Yu, P.
Subjects: Astrophysics - Instrumentation and Methods for Astrophysics, High Energy Physics - Experiment
Abstract: For the first time in the history of ground-based $\gamma$-ray astronomy, the on-axis performance of the dual mirror, aspheric, aplanatic Schwarzschild-Couder optical system has been demonstrated in a $9.7$-m aperture imaging atmospheric Cherenkov telescope. The novel design of the prototype Schwarzschild-Couder Telescope (pSCT) is motivated by the need of the next-generation Cherenkov Telescope Array (CTA) observatory to have the ability to perform wide ($\geq 8^{\circ}$) field-of-view observations simultaneously with superior imaging of atmospheric cascades (resolution of $0.067^{\circ}$ per pixel or better). The pSCT design, if implemented in the CTA installation, has the potential to improve significantly both the $\gamma$-ray angular resolution and the off-axis sensitivity of the observatory, reaching nearly the theoretical limit of the technique and thereby making a major impact on the CTA observatory sky survey programs, follow-up observations of multi-messenger transients with poorly known initial localization, as well as on the spatially resolved spectroscopic studies of extended $\gamma$-ray sources. This contribution reports on the initial alignment procedures and point-spread-function results for the challenging segmented aspheric primary and secondary mirrors of the pSCT., Comment: 19 pages, 11 figures, proceedings for SPIE Optical Engineering + Applications, 2020, Online Only
Published: 2020
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43. Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation

Author: Consortium, The Cherenkov Telescope Array, Abdalla, H., Abe, H., Acero, F., Acharyya, A., Adam, R., Agudo, I., Aguirre-Santaella, A., Alfaro, R., Alfaro, J., Alispach, C., Aloisio, R., B, R. Alves, Amati, L., Amato, E., Ambrosi, G., Angüner, E. O., Araudo, A., Armstrong, T., Arqueros, F., Arrabito, L., Asano, K., Ascasíbar, Y., Ashley, M., Backes, M., Balazs, C., Balbo, M., Balmaverde, B., Larriva, A. Baquero, Martins, V. Barbosa, Barkov, M., Baroncelli, L., de Almeida, U. Barres, Barrio, J. A., Batista, P., Becerra, J., Becherini, Y., Beck, G., Tjus, J. Becker, Belmont, R., Benbow, W., Bernardini, E., Berti, A., Berton, M., Bertucci, B., Beshley, V., Bi, B., Biasuzzi, B., Biland, A., Bissaldi, E., Biteau, J., Blanch, O., Bocchino, F., Boisson, C., Bolmont, J., Bonanno, G., Arbeletche, L. Bonneau, Bonnoli, G., Bordas, P., Bottacini, E., Böttcher, M., Bozhilov, V., Bregeon, J., Brill, A., Brown, A. M., Bruno, P., Bruno, A., Bulgarelli, A., Burton, M., Buscemi, M., Caccianiga, A., Cameron, R., Capasso, M., Caprai, M., Caproni, A., Capuzzo-Dolcetta, R., Caraveo, P., Carosi, R., Carosi, A., Casanova, S., Cascone, E., Cauz, D., Cerny, K., Cerruti, M., Chadwick, P., Chaty, S., Chen, A., Chernyakova, M., Chiaro, G., Chiavassa, A., Chytka, L., Conforti, V., Conte, F., Contreras, J. L., Coronado-Blazquez, J., Cortina, J., Costa, A., Costantini, H., Covino, S., Cristofari, P., Cuevas, O., D'Ammando, F., Daniel, M. K., Davies, J., Dazzi, F., De Angelis, A., de Lavergne, M. de Bony, De Caprio, V., Anjos, R. de Cássia dos, Pino, E. M. de Gouveia Dal, De Lotto, B., De Martino, D., de Naurois, M., Wilhelmi, E. de Oña, De Palma, F., de Souza, V., Delgado, C., Della Ceca, R., della Volpe, D., Depaoli, D., Di Girolamo, T., Di Pierro, F., Díaz, C., Díaz-Bahamondes, C., Diebold, S., Djannati-Ataï, A., Dmytriiev, A., Domínguez, A., Donini, A., Dorner, D., Doro, M., Dournaux, J., Dwarkadas, V. V., Ebr, J., Eckner, C., Einecke, S., Ekoume, T. R. N., Elsässer, D., Emery, G., Evoli, C., Fairbairn, M., Falceta-Goncalves, D., Fegan, S., Feng, Q., Ferrand, G., Fiandrini, E., Fiasson, A., Fioretti, V., Foffano, L., Fonseca, M. V., Font, L., Fontaine, G., Franco, F. J., Coromina, L. Freixas, Fukami, S., Fukazawa, Y., Fukui, Y., Gaggero, D., Galanti, G., Gammaldi, V., Garcia, E., Garczarczyk, M., Gascon, D., Gaug, M., Gent, A., Ghalumyan, A., Ghirlanda, G., Gianotti, F., Giarrusso, M., Giavitto, G., Giglietto, N., Giordano, F., Glicenstein, J., Goldoni, P., González, J. M., Gourgouliatos, K., Grabarczyk, T., Grandi, P., Granot, J., Grasso, D., Green, J., Grube, J., Gueta, O., Gunji, S., Halim, A., Harvey, M., Collado, T. Hassan, Hayashi, K., Heller, M., Cadena, S. Hernández, Hervet, O., Hinton, J., Hiroshima, N., Hnatyk, B., Hnatyk, R., Hoffmann, D., Hofmann, W., Holder, J., Horan, D., Hörandel, J., Horvath, P., Hovatta, T., Hrabovsky, M., Hrupec, D., Hughes, G., Hütten, M., Iarlori, M., Inada, T., Inoue, S., Insolia, A., Ionica, M., Iori, M., Jacquemont, M., Jamrozy, M., Janecek, P., Martínez, I. Jiménez, Jin, W., Jung-Richardt, I., Jurysek, J., Kaaret, P., Karas, V., Karkar, S., Kawanaka, N., Kerszberg, D., Khélifi, B., Kissmann, R., Knödlseder, J., Kobayashi, Y., Kohri, K., Komin, N., Kong, A., Kosack, K., Kubo, H., La Palombara, N., Lamanna, G., Lang, R. G., Lapington, J., Laporte, P., Lemoine-Goumard, M., Lenain, J., Leone, F., Leto, G., Leuschner, F., Lindfors, E., Lloyd, S., Lohse, T., Lombardi, S., Longo, F., Lopez, A., López, M., López-Coto, R., Loporchio, S., Lucarelli, F., Luque-Escamilla, P. L., Lyard, E., Maggio, C., Majczyna, A., Makariev, M., Mallamaci, M., Mandat, D., Maneva, G., Manganaro, M., Manicò, G., Marcowith, A., Marculewicz, M., Markoff, S., Marquez, P., Martí, J., Martinez, O., Martínez, M., Martínez, G., Martínez-Huerta, H., Maurin, G., Mazin, D., Mbarubucyeye, J. D., Miranda, D. Medina, Meyer, M., Micanovic, S., Miener, T., Minev, M., Miranda, J. M., Mitchell, A., Mizuno, T., Mode, B., Moderski, R., Mohrmann, L., Molina, E., Montaruli, T., Moralejo, A., Merino, J. Morales, Morcuende-Parrilla, D., Morselli, A., Mukherjee, R., Mundell, C., Murach, T., Muraishi, H., Nagai, A., Nakamori, T., Nemmen, R., Niemiec, J., Nieto, D., Nievas, M., Nikołajuk, M., Nishijima, K., Noda, K., Nosek, D., Nozaki, S., O'Brien, P., Ohira, Y., Ohishi, M., Oka, T., Ong, R. A., Orienti, M., Orito, R., Orlandini, M., Orlando, E., Osborne, J. P., Ostrowski, M., Oya, I., Pagliaro, A., Palatka, M., Paneque, D., Pantaleo, F. R., Paredes, J. M., Parmiggiani, N., Patricelli, B., Pavletić, L., Pe'er, A., Pech, M., Pecimotika, M., Peresano, M., Persic, M., Petruk, O., Pfrang, K., Piatteli, P., Pietropaolo, E., Pillera, R., Pilszyk, B., Pimentel, D., Pintore, F., Pita, S., Pohl, M., Poireau, V., Polo, M., Prado, R. R., Prast, J., Principe, G., Produit, N., Prokoph, H., Prouza, M., Przybilski, H., Pueschel, E., Pühlhofer, G., Pumo, M. L., Punch, M., Queiroz, F., Quirrenbach, A., Rando, R., Razzaque, S., Rebert, E., Recchia, S., Reichherzer, P., Reimer, O., Reimer, A., Renier, Y., Reposeur, T., Rhode, W., Ribeiro, D., Ribó, M., Richtler, T., Rico, J., Rieger, F., Rizi, V., Rodriguez, J., Fernandez, G. Rodriguez, Ramirez, J. C. Rodriguez, Vázquez, J. J. Rodríguez, Romano, P., Romeo, G., Roncadelli, M., Rosado, J., de Leon, A. Rosales, Rowell, G., Rudak, B., Rujopakarn, W., Russo, F., Sadeh, I., Saha, L., Saito, T., Greus, F. Salesa, Sanchez, D., Sánchez-Conde, M., Sangiorgi, P., Sano, H., Santander, M., Santos, E. M., Sanuy, A., Sarkar, S., Saturni, F. G., Sawangwit, U., Scherer, A., Schleicher, B., Schovanek, P., Schussler, F., Schwanke, U., Sciacca, E., Scuderi, S., Arroyo, M. Seglar, Sergijenko, O., Servillat, M., Seweryn, K., Shalchi, A., Sharma, P., Shellard, R. C., Siejkowski, H., Sinha, A., Sliusar, V., Slowikowska, A., Sokolenko, A., Sol, H., Specovius, A., Spencer, S., Spiga, D., Stamerra, A., Stanič, S., Starling, R., Stolarczyk, T., Straumann, U., Strišković, J., Suda, Y., Świerk, P., Tagliaferri, G., Takahashi, H., Takahashi, M., Tavecchio, F., Taylor, L., Tejedor, L. A., Temnikov, P., Terrier, R., Terzic, T., Testa, V., Tian, W., Tibaldo, L., Tonev, D., Torres, D. F., Torresi, E., Tosti, L., Tothill, N., Tovmassian, G., Travnicek, P., Truzzi, S., Tuossenel, F., Umana, G., Vacula, M., Vagelli, V., Valentino, M., Vallage, B., Vallania, P., van Eldik, C., Varner, G. S., Vassiliev, V., Acosta, M. Vázquez, Vecchi, M., Veh, J., Vercellone, S., Vergani, S., Verguilov, V., Vettolani, G. P., Viana, A., Vigorito, C. F., Vitale, V., Vorobiov, S., Vovk, I., Vuillaume, T., Wagner, S. J., Walter, R., Watson, J., White, M., White, R., Wiemann, R., Wierzcholska, A., Will, M., Williams, D. A., Wischnewski, R., Wolter, A., Yamazaki, R., Yanagita, S., Yang, L., Yoshikoshi, T., Zacharias, M., Zaharijas, G., Zaric, D., Zavrtanik, M., Zavrtanik, D., Zech, A., Zechlin, H., Zhdanov, V. I., and Živec, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for $\gamma$-ray astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of $\gamma$-ray cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of $\gamma$-ray absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift $z=2$ and to constrain or detect $\gamma$-ray halos up to intergalactic-magnetic-field strengths of at least 0.3pG. Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from $\gamma$-ray astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of $\gamma$-ray cosmology., Comment: 71 pages (including affiliations and references), 13 figures, 6 tables. Accepted in JCAP; matches published version. Corresponding authors: Jonathan Biteau, Julien Lefaucheur, Humberto Martinez-Huerta, Manuel Meyer, Santiago Pita, Ievgen Vovk
Published: 2020
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44. Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre

Author: Consortium, The Cherenkov Telescope Array, Acharyya, A., Adam, R., Adams, C., Agudo, I., Aguirre-Santaella, A., Alfaro, R., Alfaro, J., Alispach, C., Aloisio, R., Batista, R. Alves, Amati, L., Ambrosi, G., Angüner, E. O., Antonelli, L. A., Aramo, C., Araudo, A., Armstrong, T., Arqueros, F., Asano, K., Ascasíbar, Y., Ashley, M., Balazs, C., Ballester, O., Larriva, A. Baquero, Martins, V. Barbosa, Barkov, M., de Almeida, U. Barres, Barrio, J. A., Bastieri, D., Becerra, J., Beck, G., Tjus, J. Becker, Benbow, W., Benito, M., Berge, D., Bernardini, E., Bernlöhr, K., Berti, A., Bertucci, B., Beshley, V., Biasuzzi, B., Biland, A., Bissaldi, E., Biteau, J., Blanch, O., Blazek, J., Bocchino, F., Boisson, C., Arbeletche, L. Bonneau, Bordas, P., Bosnjak, Z., Bottacini, E., Bozhilov, V., Bregeon, J., Brill, A., Bringmann, T., Brown, A. M., Brun, P., Brun, F., Bruno, P., Bulgarelli, A., Burton, M., Burtovoi, A., Buscemi, M., Cameron, R., Capasso, M., Caproni, A., Capuzzo-Dolcetta, R., Caraveo, P., Carosi, R., Carosi, A., Casanova, S., Cascone, E., Cassol, F., Catalani, F., Cauz, D., Cerruti, M., Chadwick, P., Chaty, S., Chen, A., Chernyakova, M., Chiaro, G., Chiavassa, A., Chikawa, M., Chudoba, J., Çolak, M., Conforti, V., Coniglione, R., Conte, F., Contreras, J. L., Coronado-Blazquez, J., Costa, A., Costantini, H., Cotter, G., Cristofari, P., D'Aì, A., D'Ammando, F., Damone, L. A., Daniel, M. K., Dazzi, F., De Angelis, A., De Caprio, V., Anjos, R. de Cássia dos, Pino, E. M. de Gouveia Dal, De Lotto, B., De Martino, D., Wilhelmi, E. de Oña, De Palma, F., de Souza, V., Delgado, C., Giler, A. G. Delgado, della Volpe, D., Depaoli, D., Di Girolamo, T., Di Pierro, F., Di Venere, L., Diebold, S., Dmytriiev, A., Domínguez, A., Donini, A., Doro, M., Ebr, J., Eckner, C., Edwards, T. D. P., Ekoume, T. R. N., Elsässer, D., Evoli, C., Falceta-Goncalves, D., Fedorova, E., Fegan, S., Feng, Q., Ferrand, G., Ferrara, G., Fiandrini, E., Fiasson, A., Filipovic, M., Fioretti, V., Fiori, M., Foffano, L., Fontaine, G., Fornieri, O., Franco, F. J., Fukami, S., Fukui, Y., Gaggero, D., Galaz, G., Gammaldi, V., Garcia, E., Garczarczyk, M., Gascon, D., Gent, A., Ghalumyan, A., Gianotti, F., Giarrusso, M., Giavitto, G., Giglietto, N., Giordano, F., Giuliani, A., Glicenstein, J., Gnatyk, R., Goldoni, P., González, M. M., Gourgouliatos, K., Granot, J., Grasso, D., Green, J., Grillo, A., Gueta, O., Gunji, S., Halim, A., Hassan, T., Heller, M., Cadena, S. Hernández, Hiroshima, N., Hnatyk, B., Hofmann, W., Holder, J., Horan, D., Hörandel, J., Horvath, P., Hovatta, T., Hrabovsky, M., Hrupec, D., Hughes, G., Humensky, T. B., Hütten, M., Iarlori, M., Inada, T., Inoue, S., Iocco, F., Iori, M., Jamrozy, M., Janecek, P., Jin, W., Jouvin, L., Jurysek, J., Karukes, E., Katarzyński, K., Kazanas, D., Kerszberg, D., Kherlakian, M. C., Kissmann, R., Knödlseder, J., Kobayashi, Y., Kohri, K., Komin, N., Kubo, H., Kushida, J., Lamanna, G., Lapington, J., Laporte, P., de Oliveira, M. A. Leigui, Lenain, J., Leone, F., Leto, G., Lindfors, E., Lohse, T., Lombardi, S., Longo, F., Lopez, A., López, M., López-Coto, R., Loporchio, S., Luque-Escamilla, P. L., Mach, E., Maggio, C., Maier, G., Mallamaci, M., de Almeida, R. Malta Nunes, Mandat, D., Manganaro, M., Mangano, S., Manicò, G., Marculewicz, M., Mariotti, M., Markoff, S., Marquez, P., Martí, J., Martinez, O., Martínez, M., Martínez, G., Martínez-Huerta, H., Maurin, G., Mazin, D., Mbarubucyeye, J. D., Miranda, D. Medina, Meyer, M., Miceli, M., Miener, T., Minev, M., Miranda, J. M., Mirzoyan, R., Mizuno, T., Mode, B., Moderski, R., Mohrmann, L., Molina, E., Montaruli, T., Moralejo, A., Morcuende-Parrilla, D., Morselli, A., Mukherjee, R., Mundell, C., Nagai, A., Nakamori, T., Nemmen, R., Niemiec, J., Nieto, D., Nikołajuk, M., Ninci, D., Noda, K., Nosek, D., Nozaki, S., Ohira, Y., Ohishi, M., Ohtani, Y., Oka, T., Okumura, A., Ong, R. A., Orienti, M., Orito, R., Orlandini, M., Orlando, S., Orlando, E., Ostrowski, M., Oya, I., Pagano, I., Pagliaro, A., Palatiello, M., Pantaleo, F. R., Paredes, J. M., Pareschi, G., Parmiggiani, N., Patricelli, B., Pavletić, L., Pe'er, A., Pecimotika, M., Pérez-Romero, J., Persic, M., Petruk, O., Pfrang, K., Piano, G., Piatteli, P., Pietropaolo, E., Pillera, R., Pilszyk, B., Pintore, F., Pohl, M., Poireau, V., Prado, R. R., Prandini, E., Prast, J., Principe, G., Prokoph, H., Prouza, M., Przybilski, H., Pühlhofer, G., Pumo, M. L., Queiroz, F., Quirrenbach, A., Rainò, S., Rando, R., Razzaque, S., Recchia, S., Reimer, O., Reisenegger, A., Renier, Y., Rhode, W., Ribeiro, D., Ribó, M., Richtler, T., Rico, J., Rieger, F., Rinchiuso, L., Rizi, V., Rodriguez, J., Fernandez, G. Rodriguez, Ramirez, J. C. Rodriguez, Rojas, G., Romano, P., Romeo, G., Rosado, J., Rowell, G., Rudak, B., Russo, F., Sadeh, I., Hatlen, E. Sæther, Safi-Harb, S., Greus, F. Salesa, Salina, G., Sanchez, D., Sánchez-Conde, M., Sangiorgi, P., Sano, H., Santander, M., Santos, E. M., Santos-Lima, R., Sanuy, A., Sarkar, S., Saturni, F. G., Sawangwit, U., Schussler, F., Schwanke, U., Sciacca, E., Scuderi, S., Seglar-Arroyo, M., Sergijenko, O., Servillat, M., Seweryn, K., Shalchi, A., Sharma, P., Shellard, R. C., Siejkowski, H., Silk, J., Siqueira, C., Sliusar, V., Słowikowska, A., Sokolenko, A., Sol, H., Spencer, S., Stamerra, A., Stanič, S., Starling, R., Stolarczyk, T., Straumann, U., Strišković, J., Suda, Y., Suomijarvi, T., Świerk, P., Tavecchio, F., Taylor, L., Tejedor, L. A., Teshima, M., Testa, V., Tibaldo, L., Peixoto, C. J. Todero, Tokanai, F., Tonev, D., Tosti, G., Tosti, L., Tothill, N., Truzzi, S., Travnicek, P., Vagelli, V., Vallage, B., Vallania, P., van Eldik, C., Vandenbroucke, J., Varner, G. S., Vassiliev, V., Acosta, M. Vázquez, Vecchi, M., Ventura, S., Vercellone, S., Vergani, S., Verna, G., Viana, A., Vigorito, C. F., Vink, J., Vitale, V., Vorobiov, S., Vovk, I., Vuillaume, T., Wagner, S. J., Walter, R., Watson, J., Weniger, C., White, R., White, M., Wiemann, R., Wierzcholska, A., Will, M., Williams, D. A., Wischnewski, R., Yanagita, S., Yang, L., Yoshikoshi, T., Zacharias, M., Zaharijas, G., Zakaria, A. A., Zampieri, L., Zanin, R., Zaric, D., Zavrtanik, M., Zavrtanik, D., Zdziarski, A. A., Zech, A., Zechlin, H., Zhdanov, V. I., and Živec, M.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Phenomenology
Abstract: We provide an updated assessment of the power of the Cherenkov Telescope Array (CTA) to search for thermally produced dark matter at the TeV scale, via the associated gamma-ray signal from pair-annihilating dark matter particles in the region around the Galactic centre. We find that CTA will open a new window of discovery potential, significantly extending the range of robustly testable models given a standard cuspy profile of the dark matter density distribution. Importantly, even for a cored profile, the projected sensitivity of CTA will be sufficient to probe various well-motivated models of thermally produced dark matter at the TeV scale. This is due to CTA's unprecedented sensitivity, angular and energy resolutions, and the planned observational strategy. The survey of the inner Galaxy will cover a much larger region than corresponding previous observational campaigns with imaging atmospheric Cherenkov telescopes. CTA will map with unprecedented precision the large-scale diffuse emission in high-energy gamma rays, constituting a background for dark matter searches for which we adopt state-of-the-art models based on current data. Throughout our analysis, we use up-to-date event reconstruction Monte Carlo tools developed by the CTA consortium, and pay special attention to quantifying the level of instrumental systematic uncertainties, as well as background template systematic errors, required to probe thermally produced dark matter at these energies. "Full likelihood tables complementing our analysis are provided here [ https://doi.org/10.5281/zenodo.4057987 ]", Comment: 68 pages (including references) and 26 figures; text identical to the version published in JCAP
Published: 2020
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45. 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
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46. 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
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47. Drive-by damage detection methodology for high-speed railway bridges applying Mel-frequency cepstral coefficients

Author: Souza, E.F., primary, Bittencourt, T.N., additional, Ames, I., additional, Ribeiro, D., additional, and Carvalho, H., additional
Published: 2023
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48. 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
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49. Brazilian Report on Safeguards Application of Reactor Neutrinos

Author: Kemp, E., Alfonzo, J. A. M., Anjos, J. C., Cernicchiaro, G., Chimenti, P., Costa, I. A., Farias, P. C. M. A., Fernandes Jr., A., Guedes, G. P., Gonzalez, L. F. G., Lima Jr., H. P., Lopes Jr., A. S., Marcelo, J., Migliorini, M. L., Nóbrega, R. A., Pepe, I. M., Ribeiro, D. B. S., Santos, W. V., Souza, D. M., Teixeira, L. R., and Trzeciak, A. M.
Subjects: Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract: The Neutrinos Angra Experiment is a water-based Cherenkov detector located in the Angra dos Reis nuclear power plant. The experiment has completed a major step by finishing the commissioning of the detector and the data acquisition system at the experimental site. The experiment was designed to detect the electron antineutrinos produced by the nuclear reactor with the main purpose to demonstrate the feasibility of monitoring the reactor activity using an antineutrino detector. This effort is within the context of the International Atomic Energy Agency (IAEA) program to identify potential and novel technologies that can be applied for non-proliferation safeguards. Challenges, such as operating at the surface, therefore with huge noise rates, and the need to build very sensitive but small-scale detectors, make the Angra experiment an excellent platform for developing the application itself, as well as acquiring expertise in new technologies and analysis methods. In this report, we describe the main detector features and the electronics chain (front-end and data acquisition). We also report preliminary physics results obtained from the commissioning phase data. Finally, we address conclusions regarding the future perspectives to keep this program active, due to its importance in the insertion of Latin-American scientists and engineers in a world-scale cutting edge scientific program., Comment: arXiv admin note: substantial text overlap with arXiv:1812.11604
Published: 2019

50. 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
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