8 research outputs found
VERITAS follow-up observation of the BL Lac blazar B2 1811+31 2020 Flare
No full textFull Author List VERITAS Collaboration :- A. Acharyya, C. B. Adams, A. Archer, P. Bangale, J. T. Bartkoske, P. Batista, W. Benbow, J. L. Christiansen, A. J. Chromey, A. Duerr, M. Errando, Q. Feng, G. M. Foote, L. Fortson, A. Furniss, C. Hahn, W. Hanlon, O. Hervet, C. E. Hinrichs, J. Hoang, J. Holder, Z. Hughes, T. B. Humensky, W. Jin, M. N. Johnson, M. Kertzman, M. Kherlakian, D. Kieda, T. K. Kleiner, N. Korzoun, S. Kumar, M. J. Lang, M. Lundy, G. Maier, C. E McGrath, E. T. Meyer, M. J. Millard, C. L. Mooney, P. Moriarty, R. Mukherjee, S. O’Brien, R. A. Ong, N. Park, C. Poggemann, M. Pohl, E. Pueschel, J. Quinn, P. L. Rabinowitz, K. Ragan, P. T. Reynolds, D. Ribeiro, E. Roache, J. L. Ryan, I. Sadeh, A. C. Sadun, L. Saha, M. Santander, G. H. Sembroski, R. Shang, M. Splettstoesser, A. K. Talluri, J. V. Tucci, V. V. Vassiliev, A. Weinstein, D. A. Williams, S. L. Wong, and J. Woo38th International Cosmic Ray Conference (ICRC2023), 26 July - 3 August, 2023, Nagoya, JapanVERITAS is an imaging atmospheric Cherenkov telescope (IACT) array most sensitive to gamma rays in the very-high-energy (VHE) energy band (85 GeV - 50 TeV). As a part of its active galactic nuclei (AGN) program, VERITAS focuses on the identification and follow-up of AGN flares reported by other multiwavelength observatories. Between October 15th and October 19th, 2020, VERITAS followed up on the Fermi-LAT and MAGIC detections of a flare of the intermediate-frequency-peaked BL Lacertae (IBL) object, B2 1811+31, located at a redshift of z=0.117. In this work, we present preliminary scientific results from the analysis of B2 1811+31’s 2020 flare, including the corresponding Fermi-LAT light curve and VERITAS detection analysis.This research is supported by grants from the U.S. Department of Energy Office of Science, the
U.S. National Science Foundation and the Smithsonian Institution, by NSERC in Canada, and by
the Helmholtz Association in Germany. This research used resources provided by the Open Science
Grid, which is supported by the National Science Foundation and the U.S. Department of Energy’s
Office of Science, and resources of the National Energy Research Scientific Computing Center
(NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract
No. DE-AC02-05CH11231. We acknowledge the excellent work of the technical support staff at
the Fred Lawrence Whipple Observatory and at the collaborating institutions in the construction
and operation of the instrument.https://pos.sissa.it/444/701
A Multiwavelength Study to Decipher the 2017 Flare of the Blazar OJ 287
No full textAcharyya, A. et al.--Full list of authors: 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.; 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.; 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.; VERITAS Collaboration; Jorstad, S. G.; Lico, R.; Lusen, P.; Marscher, A. P.In 2017 February, the blazar OJ 287 underwent a period of intense multiwavelength activity. It reached a new historic peak in the soft X-ray (0.3–10 keV) band, as measured by the Swift X-ray Telescope. This event coincides with a very-high-energy (VHE) γ-ray outburst that led VERITAS to detect emission above 100 GeV, with a detection significance of 10σ (from 2016 December 9 to 2017 March 31). The time-averaged VHE γ-ray spectrum was consistent with a soft power law (Γ = −3.81 ± 0.26) and an integral flux corresponding to ∼2.4% that of the Crab Nebula above the same energy. Contemporaneous data from multiple instruments across the electromagnetic spectrum reveal a complex flaring behavior, primarily in the soft X-ray and VHE bands. To investigate the possible origin of such an event, our study focuses on three distinct activity states: before, during, and after the 2017 February peak. The spectral energy distributions during these periods suggest the presence of at least two nonthermal emission zones, with the more compact one responsible for the observed flare. Broadband modeling results and observations of a new radio knot in the jet of OJ 287 in 2017 are consistent with a flare originating from a strong recollimation shock outside the radio core. © 2024. The Author(s). Published by the American Astronomical Society.VERITAS is supported by grants from the U.S. Department of Energy Office of Science, the U.S. National Science Foundation and the Smithsonian Institution, and by NSERC in Canada. We acknowledge the excellent work of the technical support staff at the Fred Lawrence Whipple Observatory and at the collaborating institutions in the construction and operation of the instrument. O.H. thanks NSF for support under grant PHY-2011420. The authors acknowledge support from the Centre de recherche en astrophysique du Québec, un regroupement stratégique du FRQNT.Peer reviewe
Recommended from our members
VERITAS Discovery of Very High Energy Gamma-Ray Emission from S3 1227+25 and Multiwavelength Observations
No full textWe report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on 2015 May 15 with the Fermi-Large Area Telescope (LAT). A combined 5 hr VERITAS exposure on May 16 and 18 resulted in a strong 13? detection with a differential photon spectral index, "= 3.8 ± 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target-of-opportunity observations with Swift, optical photometry, polarimetry, and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of ? obs = 6.2 ± 0.9 hr, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cutoff. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
VTSCat: The VERITAS Catalog of Gamma-Ray Observations
No full textVTSCat is the catalog of high-level data products from all publications of the VERITAS collaboration . This is release version v2.0.3 adding publications from end of 2022 to mid of 2023. The VTSCat data collection contains: high-level data like spectral flux points, light curves, spectral fits in human- and machine-readable yaml and ecsv file format tabled data like upper limits tables from dark matter searches or results on the extragalactic background in ecsv file format sky maps (wherever available) in FITS file format A detailed description of VTSCat can be found in A. Acharyya et al 2023 Res. Notes AAS 7 6 . Please check also the README file and all documentation linked to the README. VTSCat supplements the HEASARC catalogue of VERITAS results, accessible through this link . VTSCat is inspired and derived from gamma-cat . If you are a previous VERITAS author and would like to be associated with this repository, please send an email to G. Maier. Access: GitHub: https://github.com/VERITAS-Observatory/VERITAS-VTSCat HEASARC: HEASARC: https://heasarc.gsfc.nasa.gov/W3Browse/all/verimaster.html References: VERITAS: https://veritas.sao.arizona.edu/ VER Dictionary of Nomenclature: https://cds.u-strasbg.fr/cgi-bin/Dic-Simbad?/17350620 ZENODO: https://doi.org/10.5281/zenodo.4723219 HEASARC: https://heasarc.gsfc.nasa.gov/W3Browse/all/verimaster.html Research note A. Acharyya et al 2023 Res. Notes AAS 7 6 ; see also arXiv:2301.04498 ICRC 2021 proceedings: https://arxiv.org/abs/2108.06424 Changes in relation with v2.0.1: fix in CITATION.cf
Broadband multi-wavelength properties of M87 during the 2018 EHT campaign including a very high energy flaring episode
No full textAlgaba, Juan-Carlos et al.-- Full list of authors: Algaba, J. C.; Baloković, 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.; lackburn, 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.; 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.; Navarro Fuentes, S.; Ni, C.; Oh, J.; Okino, H.; Olivares, H.; Oyama, T.; Özel, F.; Palumbo, D. C. M.; Filippos Paraschos, G.; 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.; Sosapanta Salas, L. D.; 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.; Cristarella Orestano, P.; 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.; Saz Parkinson, P. M.; Sgrò, C.; Siskind, E. J.; Spinelli, P.; Suson, D. J.; Tajima, H.; Torres, D. F.; Zaharijas, G.; Aharonian, F.; Ait Benkhali, F.; Aschersleben, J.; Ashkar, H.; Backes, M.; Barbosa Martins, V.; Batzofin, R.; Becherini, Y.; Berge, D.; Böttcher, M.; Boisson, C.; Bolmont, J.; de Bony de Lavergne, M.; 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.; Cotter, G.; Damascene Mbarubucyeye, J.; Devin, J.; Djuvsland, J.; Dmytriiev, A.; Einecke, S.; Ernenwein, J. -P.; Feijen, K.; Fontaine, G.; Funk, S.; Gabici, S.; Glawion, D.; Glicenstein, J. F.; Goswami, P.; Grolleron, G.; Haerer, L.; Heß, B.; Holch, T. L.; Holler, M.; Horns, D.; Huang, Zhiqiu; Jamrozy, M.; Jankowsky, F.; Jung-Richardt, I.; Kasai, E.; Katarzyński, K.; Khatoon, R.; Khélifi, B.; Kluźniak, W.; Komin, Nu.; Kosack, K.; Kundu, A.; Lang, R. G.; Le Stum, S.; Leitl, F.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J. -P.; Leuschner, F.; Luashvili, A.; Mackey, J.; Malyshev, D.; Martí-Devesa, G.; Marx, R.; Meyer, M.; Mitchell, A.; Moderski, R.; Moghadam, M. O.; Mohrmann, L.; Montanari, A.; Moulin, E.; de Naurois, M.; Niemiec, J.; O'Brien, P.; Ohm, S.; de Ona Wilhelmi, E.; Ostrowski, M.; Panny, S.; Panter, M.; Pensec, U.; Pita, S.; Pühlhofer, G.; Quirrenbach, A.; Ravikularaman, S.; Reimer, A.; Reimer, O.; Reville, B.; Reis, I.; Ren, H.; Rieger, F.; Roellinghoff, G.; Rudak, B.; Ruiz-Velasco, E.; Sabri, K.; Sahakian, V.; Salzmann, H.; Santangelo, A.; Sasaki, M.; Schäfer, J.; Schüssler, F.; Schutte, H. M.; Shapopi, J. N. S.; Sharma, A.; Sol, H.; Spencer, S.; Stawarz, Ł.; Steppa, C.; Streil, K.; Suzuki, H.; Takahashi, T.; Tanaka, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Tsirou, M.; van Eldik, C.; Vecchi, M.; Wach, T.; Wagner, S. J.; Wierzcholska, A.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Żywucka, N.; Abe, S.; Abhir, J.; Abhishek, A.; Acciari, V. A.; Aguasca-Cabot, A.; Agudo, I.; Aniello, T.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels, A.; Arcaro, C.; Artero, M.; Asano, K.; Babić, A.; Barres de Almeida, U.; Barrio, J. A.; Batković, I.; Bautista, A.; Baxter, J.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Bernete, J.; Berti, A.; Besenrieder, J.; Bigongiari, C.; Biland, A.; Blanch, O.; Bonnoli, G.; Bošnjak, Ž.; 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.; Delgado Mendez, C.; Di Pierro, F.; Di Tria, R.; Di Venere, L.; Dominis Prester, D.; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Escudero, J.; Fariña, L.; Fattorini, A.; Foffano, L.; Font, L.; Fröse, S.; Fukami, S.; Fukazawa, Y.; García López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giesbrecht Paiva, J. G.; Giglietto, N.; Giordano, F.; Gliwny, P.; Godinović, N.; Gradetzke, T.; Grau, R.; Green, D.; Green, J. G.; Günther, P.; Hadasch, D.; Hahn, A.; Hassan, T.; Heckmann, L.; Herrera Llorente, J.; Hrupec, D.; Imazawa, R.; Ishio, K.; Jiménez Martínez, I.; Jormanainen, J.; Kayanoki, T.; Kerszberg, D.; Kluge, G. W.; Kobayashi, Y.; Kouch, P. M.; Kubo, H.; Kushida, J.; Láinez, M.; Lamastra, A.; Leone, F.; Lindfors, E.; Lombardi, S.; López-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio, S.; Lorini, A.; Lyard, E.; Machado de Oliveira Fraga, B.; 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.; Molero González, M.; Molina, E.; Mondal, H. A.; Moralejo, A.; Morcuende, D.; Nakamori, T.; Nanci, C.; Neustroev, V.; Nickel, L.; Nievas Rosillo, M.; Nigro, C.; Nikolić, L.; Nilsson, K.; Nishijima, K.; Njoh Ekoume, T.; Noda, K.; Nozaki, S.; Ohtani, Y.; Okumura, A.; Otero-Santos, J.; Paiano, S.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Peresano, M.; Persic, M.; Pihet, M.; Pirola, G.; Podobnik, F.; Prada Moroni, P. G.; 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.; Tajima, H.; Takahashi, M.; Takeishi, R.; Tavecchio, F.; Temnikov, P.; Terauchi, K.; Terzić, T.; Teshima, M.; Truzzi, S.; Tutone, A.; Ubach, S.; van Scherpenberg, J.; Vazquez Acosta, M.; 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, J.; 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.Context. The nearby elliptical galaxy M87 contains one of 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 γ-ray energies) took part in the second M87 EHT campaign.Aims. 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.Methods. 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) γ-rays as well as details of the individual observations and light curves. We also conducted phenomenological modelling to investigate the basic source properties.Results. We present the first VHE γ-ray flare from M87 detected since 2010. The flux above 350 GeV more than doubled within a period of ≈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.Conclusions. 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 γ-ray flare already presents a challenge to simple one-zone leptonic emission model approaches, and it emphasises the need for combined image and spectral modelling. © The Authors 2024The Event Horizon Telescope Collaboration thanks the following organisations and programs: the Academia Sinica;
the Academy of Finland (projects 274477, 284495, 312496,
315721); the Agencia Nacional de Investigación y Desarrollo
(ANID), Chile via NCN19_058 (TITANs), Fondecyt 1221421
and BASAL FB210003; the Alexander von Humboldt Stiftung;
an Alfred P. Sloan Research Fellowship; Allegro, the European
ALMA Regional Centre node in the Netherlands, the NL astronomy research network NOVA and the astronomy institutes of
the University of Amsterdam, Leiden University, and Radboud
University; the ALMA North America Development Fund; the
Astrophysics and High Energy Physics programme by MCIN
(with funding from European Union NextGenerationEU, PRTRC17I1); the Black Hole Initiative, that is funded by grants from
the John Templeton Foundation (60477, 61497, 62286) and the
Gordon and Betty Moore Foundation (Grant GBMF-8273) -
although the opinions expressed in this work are those of the
author and do not necessarily reflect the views of these Foundations; the Brinson Foundation; “la Caixa” Foundation (ID
100010434) through fellowship codes LCF/BQ/DI22/11940027
and LCF/BQ/DI22/11940030; Chandra DD7-18089X and
TM6-17006X; the China Scholarship Council; the China
Postdoctoral Science Foundation fellowships (2020M671266,
2022M712084); Consejo Nacional de Humanidades, Ciencia
y Tecnología (CONAHCYT, Mexico, projects U0004-246083,
U0004-259839, F0003-272050, M0037-279006, F0003-
281692, 104497, 275201, 263356); the Colfuturo Scholarship;
the Consejería de Economía, Conocimiento, Empresas y
Universidad of the Junta de Andalucía (grant P18-FR-1769),
the Consejo Superior de Investigaciones Científicas (grant
2019AEP112); the Delaney Family via the Delaney Family
John A. Wheeler Chair at Perimeter Institute; Dirección General
de Asuntos del Personal Académico-Universidad Nacional
Autónoma de México (DGAPA-UNAM, projects IN112820
and IN108324); the Dutch Organization for Scientific Research
(NWO) for the VICI award (grant 639.043.513), the grant
OCENW.KLEIN.113, and the Dutch Black Hole Consortium
(with project No. NWA 1292.19.202) of the research programme
the National Science Agenda; the Dutch National Supercomputers, Cartesius and Snellius (NWO grant 2021.013); the EACOA
Fellowship awarded by the East Asia Core Observatories
Association, which consists of the Academia Sinica Institute
of Astronomy and Astrophysics, the National Astronomical
Observatory of Japan, Center for Astronomical Mega-Science,
Chinese Academy of Sciences, and the Korea Astronomy and
Space Science Institute; the European Research Council (ERC)
Synergy Grant “BlackHoleCam: Imaging the Event Horizon of
Black Holes" (grant 610058); the European Union Horizon 2020
research and innovation programme under grant agreements
RadioNet (No. 730562) and M2FINDERS (No. 101018682);
the European Research Council for advanced grant ‘JETSET:
Launching, propagation and emission of relativistic jets from
binary mergers and across mass scales’ (grant No. 884631); the
Horizon ERC Grants 2021 programme under grant agreement
No. 101040021; the FAPESP (Fundação de Amparo á Pesquisa
do Estado de São Paulo) under grant 2021/01183-8; the Fondo
CAS-ANID folio CAS220010; the Generalitat Valenciana
(grants APOSTD/2018/177 and ASFAE/2022/018) and GenT
Program (project CIDEGENT/2018/021); the Gordon and Betty
Moore Foundation (GBMF-3561, GBMF-5278, GBMF-10423);
the Institute for Advanced Study; the Istituto Nazionale di
Fisica Nucleare (INFN) sezione di Napoli, iniziative specifiche
TEONGRAV; the International Max Planck Research School
for Astronomy and Astrophysics at the Universities of Bonn
and Cologne; DFG research grant “Jet physics on horizon scales
and beyond” (grant No. 443220636); Joint Columbia/Flatiron
Postdoctoral Fellowship (research at the Flatiron Institute is
supported by the Simons Foundation); the Japan Ministry of
Education, Culture, Sports, Science and Technology (MEXT;
grant JPMXP1020200109); the Japan Society for the Promotion
of Science (JSPS) Grant-in-Aid for JSPS Research Fellowship
(JP17J08829); the Joint Institute for Computational Fundamental Science, Japan; the Key Research Program of Frontier
Sciences, Chinese Academy of Sciences (CAS, grants QYZDJSSW-SLH057, QYZDJSSW-SYS008, ZDBS-LY-SLH011);
the Leverhulme Trust Early Career Research Fellowship; the
Max-Planck-Gesellschaft (MPG); the Max Planck Partner
Group of the MPG and the CAS; the MEXT/JSPS KAKENHI
(grants 18KK0090, JP21H01137, JP18H03721, JP18K13594,
18K03709, JP19K14761, 18H01245, 25120007, 19H01943,
21H01137, 21H04488, 22H00157, 23K03453); the MICINN
Research Project PID2019-108995GB-C22; the MIT International Science and Technology Initiatives (MISTI) Funds;
the Ministry of Science and Technology (MOST) of Taiwan
(103-2119-M-001-010-MY2, 105-2112-M-001-025-MY3, 105-
2119-M-001-042, 106-2112-M-001-011, 106-2119-M-001-013,
106-2119-M-001-027, 106-2923-M-001-005, 107-2119-
M-001-017, 107-2119-M-001-020, 107-2119-M-001-041,
107-2119-M-110-005, 107-2923-M-001-009, 108-2112-M001-048, 108-2112-M-001-051, 108-2923-M-001-002, 109-
2112-M-001-025, 109-2124-M-001-005, 109-2923-M-001-001,
110-2112-M-001-033, 110-2124-M-001-007, 110-2923-M-001-
001, and 112-2112-M-003-010-MY3); the National Science and
Technology Council (NSTC) of Taiwan (111-2124-M-001-005,
112-2124-M-001-014); the Ministry of Education (MoE) of
Taiwan Yushan Young Scholar Program; the Physics Division, National Center for Theoretical Sciences of Taiwan; the
National Aeronautics and Space Administration (NASA, Fermi
Guest Investigator grant 80NSSC23K1508, NASA Astrophysics
Theory Program grant 80NSSC20K0527, NASA NuSTAR
award 80NSSC20K0645); NASA Hubble Fellowship grants
HST-HF2-51431.001-A, HST-HF2-51482.001-A awarded by
the Space Telescope Science Institute, which is operated by
the Association of Universities for Research in Astronomy,
Inc., for NASA, under contract NAS5-26555; the National
Institute of Natural Sciences (NINS) of Japan; the National
Key Research and Development Program of China (grant
2016YFA0400704, 2017YFA0402703, 2016YFA0400702); the
National Science and Technology Council (NSTC, grants NSTC
111-2112-M-001 -041, NSTC 111-2124-M-001-005, NSTC
112-2124-M-001-014); the US National Science Foundation
(NSF, grants AST-0096454, AST-0352953, AST-0521233,
AST-0705062, AST-0905844, AST-0922984, AST-1126433,
OIA-1126433, AST-1140030, DGE-1144085, AST-1207704,
AST-1207730, AST-1207752, MRI-1228509, OPP-1248097,
AST-1310896, AST-1440254, AST-1555365, AST-1614868,
AST-1615796, AST-1715061, AST-1716327, AST-1726637,
OISE-1743747, AST-1743747, AST-1816420, AST-1935980,
AST-1952099, AST-2034306, AST-2205908, AST-2307887);
NSF Astronomy and Astrophysics Postdoctoral Fellowship
(AST-1903847); the Natural Science Foundation of China
(grants 11650110427, 10625314, 11721303, 11725312,
11873028, 11933007, 11991052, 11991053, 12192220,
12192223, 12273022, 12325302); the Natural Sciences and
Engineering Research Council of Canada (NSERC, including
a Discovery Grant and the NSERC Alexander Graham Bell
Canada Graduate Scholarships-Doctoral Program); the National
Research Foundation of Korea (the Global PhD Fellowship
Grant: grants NRF-2015H1A2A1033752, the Korea Research
Fellowship Program: NRF-2015H1D3A1066561, Brain Pool
Program: 2019H1D3A1A01102564, Basic Research Support Grant 2019R1F1A1059721, 2021R1A6A3A01086420,
2022R1C1C1005255, 2022R1F1A1075115); Netherlands
Research School for Astronomy (NOVA) Virtual Institute of
Accretion (VIA) postdoctoral fellowships; NOIRLab, which
is managed by the Association of Universities for Research
in Astronomy (AURA) under a cooperative agreement with
the National Science Foundation; Onsala Space Observatory
(OSO) national infrastructure, for the provisioning of its
facilities/observational support (OSO receives funding through
the Swedish Research Council under grant 2017-00648);
the Perimeter Institute for Theoretical Physics (research at
Perimeter Institute is supported by the Government of Canada
through the Department of Innovation, Science and Economic
Development and by the Province of Ontario through the
Ministry of Research, Innovation and Science); the Princeton
Gravity Initiative; the Spanish Ministerio de Ciencia e Innovación (grants PGC2018-098915-B-C21, AYA2016-80889-P,
PID2019-108995GB-C21, PID2020-117404GB-C21); the
University of Pretoria for financial aid in the provision of
the new Cluster Server nodes and SuperMicro (USA) for a
SEEDING GRANT approved toward these nodes in 2020; the
Shanghai Municipality orientation program of basic research for
international scientists (grant no. 22JC1410600); the Shanghai
Pilot Program for Basic Research, Chinese Academy of Science,
Shanghai Branch (JCYJ-SHFY-2021-013); the State Agency
for Research of the Spanish MCIU through the “Center of
Excellence Severo Ochoa” award for the Instituto de Astrofísica
de Andalucía (SEV-2017- 0709); the Spanish Ministry for
Science and Innovation grant CEX2021-001131-S funded by
MCIN/AEI/10.13039/501100011033; the Spinoza Prize SPI
78-409; the South African Research Chairs Initiative, through
the South African Radio Astronomy Observatory (SARAO,
grant ID 77948), which
