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VHE gamma-ray detection of FSRQ QSO B1420+326 and modeling of its enhanced broadband state in 2020

Acciari, V. A. and Ansoldi, S. and Antonelli, L. A. and Arbet Engels, A. and Artero, M. and Asano, K. and Baack, D. and Babić, A. and Baquero, A. and Barres de Almeida, U. and Barrio, J. A. and Becerra González, J. and Bednarek, W. and Bellizzi, L. and Bernardini, E. and Bernardos, M. and Berti, A. and Besenrieder, J. and Bhattacharyya, W. and Bigongiari, C. and Biland, A. and Blanch, O. and Bonnoli, G. and Bošnjak, Ž. and Busetto, G. and Carosi, R. and Ceribella, G. and Cerruti, M. and Chai, Y. and Chilingarian, A. and Cikota, S. and Colak, S. M. and Colombo, E. and Contreras, J. L. and Cortina, J. and Covino, S. and D'Amico, G. and D'Elia, V. and Da Vela, P. and Dazzi, F. and De Angelis, A. and De Lotto, B. and Delfino, M. and Delgado, J. and Delgado Mendez, C. and Depaoli, D. and Di Pierro, F. and Di Venere, L. and Do Souto Espiñeira, E. and Dominis Prester, D. and Donini, A. and Dorner, D. and Doro, M. and Elsaesser, D. and Fallah Ramazani, V. and Fattorini, A. and Ferrara, G. and Foffano, L. and Fonseca, M. V. and Font, L. and Fruck, C. and Fukami, S. and García López, R. J. and Garczarczyk, M. and Gasparyan, S. and Gaug, M. and Giglietto, N. and Giordano, F. and Gliwny, P. and Godinović, N. and Green, J. G. and Green, D. and Hadasch, D. and Hahn, A. and Heckmann, L. and Herrera, J. and Hoang, J. and Hrupec, D. and Hütten, M. and Inada, T. and Inoue, S. and Ishio, K. and Iwamura, Y. and Jormanainen, J. and Jouvin, L. and Kajiwara, Y. and Karjalainen, M. and Kerszberg, D. and Kobayashi, Y. and Kubo, H. and Kushida, J. and Lamastra, A. and Lelas, D. and Leone, F. and Lindfors, E. and Lombardi, S. and Longo, F. and López-Coto, R. and López-Moya, M. and López-Oramas, A. and Loporchio, S. and Machado de Oliveira Fraga, B. and Maggio, C. and Majumdar, P. and Makariev, M. and Mallamaci, M. and Maneva, G. and Manganaro, M. and Mannheim, K. and Maraschi, L. and Mariotti, M. and Martínez, M. and Mazin, D. and Mender, S. and Mićanović, S. and Miceli, D. and Miener, T. and Minev, M. and Miranda, J. M. and Mirzoyan, R. and Molina, E. and Moralejo, A. and Morcuende, D. and Moreno, V. and Moretti, E. and Neustroev, V. and Nigro, C. and Nilsson, K. and Ninci, D. and Nishijima, K. and Noda, K. and Nozaki, S. and Ohtani, Y. and Oka, T. and Otero-Santos, J. and Paiano, S. and Palatiello, M. and Paneque, D. and Paoletti, R. and Paredes, J. M. and Pavletić, L. and Peñil, P. and Perennes, C. and Persic, M. and Prada Moroni, P. G. and Prandini, E. and Priyadarshi, C. and Puljak, I. and Rhode, W. and Ribó, M. and Rico, J. and Righi, C. and Rugliancich, A. and Saha, L. and Sahakyan, N. and Saito, T. and Sakurai, S. and Satalecka, K. and Saturni, F. G. and Schleicher, B. and Schmidt, K. and Schweizer, T. and Sitarek, J. and Šnidarić, I. and Sobczynska, D. and Spolon, A. and Stamerra, A. and Strom, D. and Strzys, M. and Suda, Y. and Surić, T. and Takahashi, M. and Tavecchio, F. and Temnikov, P. and Terzić, T. and Teshima, M. and Torres-Albà, N. and Tosti, L. and Truzzi, S. and Tutone, A. and van Scherpenberg, J. and Vanzo, G. and Vazquez Acosta, M. and Ventura, S. and Verguilov, V. and Vigorito, C. F. and Vitale, V. and Vovk, I. and Will, M. and Zarić, D. and Angioni, R. and D'Ammando, F. and Ciprini, S. and Cheung, C. C. and Orienti, M. and Pacciani, L. and Prajapati, P. and Kumar, P. and Ganesh, S. and Minev, M. and Kurtenkov, A. and Marchini, A. and Carrasco, L. and Escobedo, G. and Porras, A. and Recillas, E. and Lähteenmäki, A. and Tornikoski, M. and Berton, M. and Tammi, J. and Vera, R. J. C. and Jorstad, S. G. and Marscher, A. P. and Weaver, Z. R. and Hart, M. and Hallum, M. K. and Larionov, V. M. and Borman, G. A. and Grishina, T. S. and Kopatskaya, E. N. and Larionova, E. G. and Nikiforova, A. A. and Morozova, D. A. and Savchenko, S. S. and Troitskaya, Yu. V. and Troitsky, I. S. and Vasilyev, A. A. and Hodges, M. and Hovatta, T. and Kiehlmann, S. and Max-Moerbeck, W. and Readhead, A. C. S. and Reeves, R. and Pearson, T. J. (2021) VHE gamma-ray detection of FSRQ QSO B1420+326 and modeling of its enhanced broadband state in 2020. Astronomy and Astrophysics, 647 . Art. No. A163. ISSN 0004-6361. doi:10.1051/0004-6361/202039687.

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Context. QSO B1420+326 is a blazar classified as a flat-spectrum radio quasar (FSRQ). At the beginning of the year 2020, it was found to be in an enhanced flux state and an extensive multiwavelength campaign allowed us to trace the evolution of the flare. Aims. We search for very high-energy (VHE) gamma-ray emission from QSO B1420+326 during this flaring state. We aim to characterize and model the broadband emission of the source over different phases of the flare. Methods. The source was observed with a number of instruments in radio, near-infrared, optical (including polarimetry and spectroscopy), ultraviolet, X-ray, and gamma-ray bands. We use dedicated optical spectroscopy results to estimate the accretion disk and the dust torus luminosity. We performed spectral energy distribution modeling in the framework of combined synchrotron-self-Compton and external Compton scenario in which the electron energy distribution is partially determined from acceleration and cooling processes. Results. During the enhanced state, the flux of both SED components of QSO B1420+326 drastically increased and the peaks were shifted to higher energies. Follow-up observations with the MAGIC telescopes led to the detection of VHE gamma-ray emission from this source, making it one of only a handful of FSRQs known in this energy range. Modeling allows us to constrain the evolution of the magnetic field and electron energy distribution in the emission region. The gamma-ray flare was accompanied by a rotation of the optical polarization vector during a low -polarization state. Also, a new superluminal radio knot contemporaneously appeared in the radio image of the jet. The optical spectroscopy shows a prominent FeII bump with flux evolving together with the continuum emission and a MgII line with varying equivalent width.

Item Type:Article
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URLURL TypeDescription Paper
Acciari, V. A.0000-0001-8307-2007
Ansoldi, S.0000-0002-5613-7693
Antonelli, L. A.0000-0002-5037-9034
Arbet Engels, A.0000-0001-9076-9582
Baack, D.0000-0002-2311-4460
Babić, A.0000-0002-1444-5604
Barres de Almeida, U.0000-0001-7909-588X
Barrio, J. A.0000-0002-0965-0259
Becerra González, J.0000-0002-6729-9022
Bednarek, W.0000-0003-0605-108X
Bernardini, E.0000-0003-3108-1141
Berti, A.0000-0003-0396-4190
Bhattacharyya, W.0000-0003-4751-0414
Bigongiari, C.0000-0003-3293-8522
Biland, A.0000-0002-1288-833X
Blanch, O.0000-0002-8380-1633
Bonnoli, G.0000-0003-2464-9077
Bošnjak, Ž.0000-0001-6536-0320
Busetto, G.0000-0002-2687-6380
Carosi, R.0000-0002-4137-4370
Cerruti, M.0000-0001-7891-699X
Chai, Y.0000-0003-2816-2821
Chilingarian, A.0000-0002-2018-9715
Cikota, S.0000-0001-7101-9831
Colak, S. M.0000-0001-7793-3106
Colombo, E.0000-0002-3700-3745
Contreras, J. L.0000-0001-7282-2394
Cortina, J.0000-0003-4576-0452
Covino, S.0000-0001-9078-5507
Dazzi, F.0000-0001-5409-6544
De Angelis, A.0000-0002-3288-2517
De Lotto, B.0000-0003-3624-4480
Delfino, M.0000-0002-9468-4751
Delgado, J.0000-0002-0166-5464
Depaoli, D.0000-0002-2672-4141
Di Pierro, F.0000-0003-4861-432X
Di Venere, L.0000-0003-0703-824X
Do Souto Espiñeira, E.0000-0001-6974-2676
Dominis Prester, D.0000-0002-9880-5039
Donini, A.0000-0002-3066-724X
Dorner, D.0000-0001-8823-479X
Doro, M.0000-0001-9104-3214
Elsaesser, D.0000-0001-6796-3205
Fallah Ramazani, V.0000-0001-8991-7744
Ferrara, G.0000-0002-1137-6252
Foffano, L.0000-0002-0709-9707
Fonseca, M. V.0000-0003-2235-0725
Font, L.0000-0003-2109-5961
Fruck, C.0000-0001-5880-7518
García López, R. J.0000-0002-8204-6832
Garczarczyk, M.0000-0002-0445-4566
Gaug, M.0000-0001-8442-7877
Giglietto, N.0000-0002-9021-2888
Giordano, F.0000-0002-8651-2394
Gliwny, P.0000-0002-4183-391X
Godinović, N.0000-0002-4674-9450
Green, D.0000-0003-0768-2203
Hadasch, D.0000-0001-8663-6461
Hahn, A.0000-0003-0827-5642
Herrera, J.0000-0002-3771-4918
Hoang, J.0000-0001-5591-5927
Hrupec, D.0000-0002-7027-5021
Hütten, M.0000-0002-2133-5251
Inoue, S.0000-0003-1096-9424
Jouvin, L.0000-0001-5119-8537
Kerszberg, D.0000-0002-5289-1509
Kubo, H.0000-0001-9159-9853
Kushida, J.0000-0002-8002-8585
Lamastra, A.0000-0003-2403-913X
Lelas, D.0000-0002-8269-5760
Leone, F.0000-0001-7626-3788
Lindfors, E.0000-0002-9155-6199
Lombardi, S.0000-0002-6336-865X
Longo, F.0000-0003-2501-2270
López-Coto, R.0000-0002-3882-9477
López-Oramas, A.0000-0003-4603-1884
Loporchio, S.0000-0003-4457-5431
Machado de Oliveira Fraga, B.0000-0002-6395-3410
Maggio, C.0000-0003-0670-7771
Majumdar, P.0000-0002-5481-5040
Makariev, M.0000-0002-1622-3116
Mallamaci, M.0000-0003-4068-0496
Maneva, G.0000-0002-5959-4179
Manganaro, M.0000-0003-1530-3031
Mannheim, K.0000-0002-2950-6641
Mariotti, M.0000-0003-3297-4128
Martínez, M.0000-0002-9763-9155
Mazin, D.0000-0002-2010-4005
Mender, S.0000-0002-0755-0609
Mićanović, S.0000-0002-0076-3134
Miceli, D.0000-0002-2686-0098
Miranda, J. M.0000-0002-1472-9690
Mirzoyan, R.0000-0003-0163-7233
Molina, E.0000-0003-1204-5516
Moralejo, A.0000-0002-1344-9080
Morcuende, D.0000-0001-9400-0922
Moreno, V.0000-0002-8358-2098
Moretti, E.0000-0001-5477-9097
Neustroev, V.0000-0003-4772-595X
Nigro, C.0000-0001-8375-1907
Nilsson, K.0000-0002-1445-8683
Ninci, D.0000-0002-5031-1849
Nishijima, K.0000-0002-1830-4251
Noda, K.0000-0003-1397-6478
Nozaki, S.0000-0002-6246-2767
Oka, T.0000-0002-9924-9978
Otero-Santos, J.0000-0002-4241-5875
Palatiello, M.0000-0002-4124-5747
Paneque, D.0000-0002-2830-0502
Paoletti, R.0000-0003-0158-2826
Paredes, J. M.0000-0002-1566-9044
Pavletić, L.0000-0002-9926-0405
Persic, M.0000-0003-1853-4900
Prada Moroni, P. G.0000-0001-9712-9916
Prandini, E.0000-0003-4502-9053
Puljak, I.0000-0001-7387-3812
Rhode, W.0000-0003-2636-5000
Ribó, M.0000-0002-9931-4557
Rico, J.0000-0003-4137-1134
Righi, C.0000-0002-1218-9555
Rugliancich, A.0000-0001-5471-4701
Saha, L.0000-0002-3171-5039
Sahakyan, N.0000-0003-2011-2731
Satalecka, K.0000-0002-7669-266X
Schmidt, K.0000-0002-3418-7251
Schweizer, T.0000-0002-1659-5374
Sitarek, J.0000-0002-1659-5374
Sobczynska, D.0000-0003-4973-7903
Spolon, A.0000-0001-8770-9503
Stamerra, A.0000-0002-9430-5264
Strom, D.0000-0003-2108-3311
Suda, Y.0000-0002-2692-5891
Takahashi, M.0000-0002-0574-6018
Tavecchio, F.0000-0003-0256-0995
Temnikov, P.0000-0002-9559-3384
Terzić, T.0000-0002-4209-3407
Torres-Albà, N.0000-0003-3638-8943
van Scherpenberg, J.0000-0002-6173-867X
Vanzo, G.0000-0003-1539-3268
Vazquez Acosta, M.0000-0002-2409-9792
Ventura, S.0000-0001-7065-5342
Verguilov, V.0000-0001-7911-1093
Vigorito, C. F.0000-0002-0069-9195
Vitale, V.0000-0001-8040-7852
Vovk, I.0000-0003-3444-3830
Will, M.0000-0002-7504-2083
Zarić, D.0000-0001-5763-9487
Angioni, R.0000-0003-4571-5192
Marchini, A.0000-0003-3779-6762
Lähteenmäki, A.0000-0002-0393-0647
Tornikoski, M.0000-0003-1249-6026
Berton, M.0000-0002-1058-9109
Jorstad, S. G.0000-0001-6158-1708
Marscher, A. P.0000-0001-7396-3332
Weaver, Z. R.0000-0001-6314-0690
Larionov, V. M.0000-0002-4640-4356
Hovatta, T.0000-0002-2024-8199
Kiehlmann, S.0000-0001-6314-9177
Max-Moerbeck, W.0000-0002-5491-5244
Readhead, A. C. S.0000-0001-9152-961X
Reeves, R.0000-0001-5704-271X
Pearson, T. J.0000-0001-5213-6231
Additional Information:© 2021 ESO. Received: 15 October 2020; Accepted: 18 December 2020; Published online 29 March 2021. We would like to dedicate this paper to the memory of our friend and colleague, Dr. Valeri Larionov (1950−2020), who enthusiastically contributed to this and many other projects aimed at understanding blazars. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF and MPG; the Italian INFN and INAF; the Swiss National Fund SNF; the ERDF under the Spanish MINECO (FPA2017-87859-P, FPA2017-85668-P, FPA2017-82729-C6-2-R, FPA2017-82729-C6-6-R, FPA2017-82729-C6-5-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2017-87055-C2-2-P, FPA2017-90566-REDC); the Indian Department of Atomic Energy; the Japanese ICRR, the University of Tokyo, JSPS, and MEXT; the Bulgarian Ministry of Education and Science, National RI Roadmap Project DO1-268/16.12.2019 and the Academy of Finland grant nr. 320045 is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia “Severo Ochoa” SEV-2016-0588 and SEV-2015-0548, the Unidad de Excelencia “María de Maeztu” MDM-2014-0369 and the “la Caixa” Foundation (fellowship LCF/BQ/PI18/11630012), by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382 and by the Brazilian MCTIC, CNPq and FAPERJ. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT, as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States; the Commissariat à l’Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France; the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy; the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK), and Japan Aerospace Exploration Agency (JAXA) in Japan; and the K. A. Wallenberg Foundation, the Swedish Research Council, and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Etudes Spatiales in France. This work was performed in part under DOE Contract DE-AC02-76SF00515. This publication makes use of data obtained at the Metsähovi Radio Observatory, operated by Aalto University in Finland. This research has made use of data from the OVRO 40 m monitoring program Richards et al. (2011) which is supported in part by NASA grants NNX08AW31G, NNX11A043G, and NNX14AQ89G and NSF grants AST-0808050 and AST-1109911. This study was based in part on observations conducted using the 1.8 m Perkins Telescope Observatory (PTO) in Arizona, which is owned and operated by Boston University. The research at Boston University was supported in part by NASA Fermi GI program grants 80NSSC17K0649, 80NSSC19K1504, and 80NSSC19K1505. We thank the ASAS-SN team for making their data publicly available. The VLBA is an instrument of the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated by Associated Universities, Inc. This work made use of the Lowell Discovery Telescope (formerly Discovery Channel Telescope) at Lowell Observatory. Lowell is a private, nonprofit institution dedicated to astrophysical research and public appreciation of astronomy and operates the LDT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University, and Yale University. We acknowledge support by Bulgarian National Science Fund under grant DN18-10/2017 and National RI Roadmap Projects DO1-277/16.12.2019 and DO1-268/16.12.2019 of the Ministry of Education and Science of the Republic of Bulgaria.
Group:Astronomy Department
Funding AgencyGrant Number
Bundesministerium für Bildung und Forschung (BMBF)UNSPECIFIED
Max Planck SocietyUNSPECIFIED
Istituto Nazionale di Fisica Nucleare (INFN)UNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Swiss National Science Foundation (SNSF)UNSPECIFIED
European Regional Development FundUNSPECIFIED
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2017-87859-P
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2017-85668-P
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2017-82729-C6-2-R
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2017-82729-C6-6-R
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2017-82729-C6-5-R
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2015-71042-P
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2016-76012-C3-1-P
Ministerio de Economía, Industria y Competitividad (MINECO)ESP2017-87055-C2-2-P
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2017-90566-REDC
Department of Atomic Energy (India)UNSPECIFIED
Institute for Cosmic Ray ResearchUNSPECIFIED
University of TokyoUNSPECIFIED
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Ministry of Education and Science (Bulgaria)DO1-268/16.12.2019
Academy of Finland320045
Centro de Excelencia Severo OchoaSEV-2016-0588
Centro de Excelencia Severo OchoaSEV-2015-0548
Ministerio de Economía, Industria y Competitividad (MINECO)MDM-2014-0369
la Caixa FoundationLCF/BQ/PI18/11630012
Croatian Science FoundationIP-2016-06-9782
University of Rijeka13.
Deutsche Forschungsgemeinschaft (DFG)SFB823/C4
Deutsche Forschungsgemeinschaft (DFG)SFB876/C3
National Science Centre (Poland)UMO-2016/22/M/ST9/00382
Ministério da Ciência, Tecnolgia, Inovação e ComunicaçõesUNSPECIFIED
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)UNSPECIFIED
Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)UNSPECIFIED
Department of Energy (DOE)DE-AC02-76SF00515
Commissariat à l’Energie Atomique (CEA)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Institut National de Physique Nucléaire et de Physique des Particules (IN2P3)UNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
High Energy Accelerator Research Organization (KEK)UNSPECIFIED
Japan Aerospace Exploration Agency (JAXA)UNSPECIFIED
Knut and Alice Wallenberg FoundationUNSPECIFIED
Swedish Research CouncilUNSPECIFIED
Swedish National Space Board (SNSB)UNSPECIFIED
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Bulgarian National Science FundDN18-10/2017
Ministry of Education and Science (Bulgaria)DO1-277/16.12.2019
Subject Keywords:gamma rays: galaxies – galaxies: jets – radiation mechanisms: non-thermal – quasars: individual: QSO B1420+326
Record Number:CaltechAUTHORS:20210202-095252065
Persistent URL:
Official Citation:VHE gamma-ray detection of FSRQ QSO B1420+326 and modeling of its enhanced broadband state in 2020 MAGIC Collaboration, V. A. Acciari, et. al. A&A, 647 (2021) A163; DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107862
Deposited By: George Porter
Deposited On:03 Feb 2021 19:05
Last Modified:31 Mar 2021 14:29

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