A1 Refereed original research article in a scientific journal
GRB 221009A: Observations with LST-1 of CTAO and Implications for Structured Jets in Long Gamma-Ray Bursts
Authors: Abe, K.; Abe, S.; Abhishek, A.; Acero, F.; Aguasca-Cabot, A.; Agudo, I.; Alispach, C.; Ambrosino, D.; Ambrosino, F.; Antonelli, L. A.; Aramo, C.; Arbet-Engels, A.; Arcaro, C.; Arnesen, T. T. H.; Asano, K.; Aubert, P.; Baktash, A.; Balbo, M.; Bamba, A.; Larriva, A. Baquero; Almeida, U. Barres de; Barrio, J. A.; Jiménez, L. Barrios; Batkovic, I.; Baxter, J.; González, J. Becerra; Bernardini, E.; Bernete, J.; Berti, A.; Bezshyiko, I.; Bigongiari, C.; Bissaldi, E.; Blanch, O.; Bonnoli, G.; Bordas, P.; Borkowski, G.; Brunelli, G.; Bulgarelli, A.; Bunse, M.; Burelli, I.; Burmistrov, L.; Cardillo, M.; Caroff, S.; Carosi, A.; Carraro, R.; Carrasco, M. S.; Cassol, F.; Cerasole, D.; Ceribella, G.; Cortínez, A. Cerviño; Chai, Y.; Cheng, K.; Chiavassa, A.; Chikawa, M.; Chon, G.; Chytka, L.; Cicciari, G. M.; Cifuentes, A.; Contreras, J. L.; Cortina, J.; Costantini, H.; Dalchenko, M.; Vela, P. Da; Dazzi, F.; Angelis, A. De; Lavergne, M. de Bony de; Burgo, R. Del; Delgado, C.; Mengual, J. Delgado; Dellaiera, M.; Volpe, D. della; Lotto, B. De; Peral, L. Del; Menezes, R. de; Palma, G. De; Díaz, C.; Piano, A. Di; Pierro, F. Di; Tria, R. Di; Venere, L. Di; Dominik, R. M.; Prester, D. Dominis; Donini, A.; Dorner, D.; Doro, M.; Eisenberger, L.; Elsässer, D.; Emery, G.; Escudero, J.; Fallah Ramazani, V.; Ferrarotto, F.; Fiasson, A.; Foffano, L.; García-Lago, F. Frías; Fröse, S.; Fukazawa, Y.; Gallozzi, S.; López, R. Garcia; Soto, S. Garcia; Gasbarra, C.; Gasparrini, D.; Geyer, D.; Paiva, J. Giesbrecht; Giglietto, N.; Giordano, F.; Godinovic, N.; Gradetzke, T.; Grau, R.; Green, D.; Green, J.; Gunji, S.; Günther, P.; Hackfeld, J.; Hadasch, D.; Hahn, A.; Hashizume, M.; Hassan, T.; Hayashi, K.; Heckmann, L.; Heller, M.; Llorente, J. Herrera; Hirotani, K.; Hoffmann, D.; Horns, D.; Houles, J.; Hrabovsky, M.; Hrupec, D.; Hui, D.; Iarlori, M.; Imazawa, R.; Inada, T.; Inome, Y.; Inoue, S.; Ioka, K.; Iori, M.; Itokawa, T.; Iuliano, A.; Jahanvi, J.; Martinez, I. Jimenez; Quiles, J. Jimenez; Rodrigo, I. Jorge; Jurysek, J.; Kagaya, M.; Kalashev, O.; Karas, V.; Katagiri, H.; Kerszberg, D.; Kiyomot, T.; Kobayashi, Y.; Kohri, K.; Kong, A.; Kornecki, P.; Kubo, H.; Kushida, J.; Lacave, B.; Lainez, M.; Lamanna, G.; Lamastra, A.; Lemoigne, L.; Linhoff, M.; Lombardi, S.; Longo, F.; López-Coto, R.; López-Moya, M.; López-Oramas, A.; Loporchio, S.; Lorini, A.; Bahilo, J. Lozano; Lucarelli, F.; Luciani, H.; Luque-Escamilla, P. L.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Mandat, D.; Manganaro, M.; Maniadakis, D. K.; Manicò, G.; Mannheim, K.; Marchesi, S.; Marini, F.; Mariotti, M.; Marquez, P.; Marsella, G.; Martí, J.; Martinez, O.; Martínez, G.; Martínez, M.; Mas-Aguilar, A.; Massa, M.; Maurin, G.; Mazin, D.; Méndez-Gallego, J.; Menon, S.; Guillen, E. Mestre; Miceli, D.; Miener, T.; Miranda, J. M.; Mirzoyan, R.; Mizote, M.; Mizuno, T.; Gonzalez, M. Molero; Molina, E.; Montaruli, T.; Moralejo, A.; Morcuende, D.; Ramos, A. Moreno; Morselli, A.; Moya, V.; Muraishi, H.; Murase, K.; Nagataki, S.; Nakamori, T.; Neronov, A.; Castaño, D. Nieto; Rosillo, M. Nievas; Nikolic, L.; Nishijima, K.; Noda, K.; Nosek, D.; Novotny, V.; Nozaki, S.; Ohishi, M.; Ohtani, Y.; Oka, T.; Okumura, A.; Orito, R.; Orsini, L.; Otero-Santos, J.; Ottanelli, P.; Palatiello, M.; Panebianco, G.; Paneque, D.; Pantaleo, F. R.; Paoletti, R.; Paredes, J. M.; Pech, M.; Pecimotika, M.; Peresano, M.; Pfeifle, F.; Pietropaolo, E.; Pihet, M.; Pirola, G.; Plard, C.; Podobnik, F.; Polo, M.; Prandini, E.; Prouza, M.; Rainò, S.; Rando, R.; Rhode, W.; Ribó, M.; Rizi, V.; Fernandez, G. Rodriguez; Frías, M. D. Rodríguez; Romano, P.; Roy, A.; Ruina, A.; Ruiz-Velasco, E.; Saito, T.; Sakurai, S.; Sanchez, D. A.; Sano, H.; Šarić, T.; Sato, Y.; Saturni, F. G.; Savchenko, V.; Schiavone, F.; Schleicher, B.; Schmuckermaier, F.; Schubert, J. L.; Schussler, F.; Schweizer, T.; Arroyo, M. Seglar; Siegert, T.; Silvestri, G.; Simongini, A.; Sitarek, J.; Sliusar, V.; Stamerra, A.; Strišković, J.; Strzys, M.; Suda, Y.; Sunny, A.; Tajima, H.; Takahashi, M.; Takata, J.; Takeishi, R.; Tam, P. H. T.; Tanaka, S. J.; Tateishi, D.; Tavernier, T.; Temnikov, P.; Terada, Y.; Terauchi, K.; Terzic, T.; Teshima, M.; Tluczykont, M.; Tokanai, F.; Tomura, T.; Torres, D. F.; Tramonti, F.; Travnicek, P.; Tripodo, G.; Tutone, A.; Vacula, M.; Scherpenberg, J. van; Acosta, M. Vázquez; Ventura, S.; Vercellone, S.; Verna, G.; Viale, I.; Vigliano, A.; Vigorito, C. F.; Visentin, E.; Vitale, V.; Voitsekhovskyi, V.; Voutsinas, G.; Vovk, I.; Vuillaume, T.; Walter, R.; Wan, L.; Will, M.; Wójtowicz, J.; Yamamoto, T.; Yamazaki, R.; Yao, Y.; Yeung, P. K. H.; Yoshida, T.; Yoshikoshi, T.; Zhang, W.; and (The CTAO-LST Collaboration)
Publisher: Institute of Physics Publishing
Publication year: 2025
Journal: Astrophysical Journal Letters
Journal name in source: The Astrophysical Journal Letters
Article number: L42
Volume: 988
Issue: 2
ISSN: 2041-8205
eISSN: 2041-8213
DOI: https://doi.org/10.3847/2041-8213/ade4cf
Web address : https://doi.org/10.3847/2041-8213/ade4cf
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/499739966
GRB 221009A is the brightest gamma-ray burst (GRB) observed to date. Extensive observations of its afterglow emission across the electromagnetic spectrum were performed, providing the first strong evidence of a jet with a nontrivial angular structure in a long GRB. We carried out an extensive observation campaign in very-high-energy (VHE) gamma rays with the first Large-Sized Telescope of the future Cherenkov Telescope Array Observatory starting on 2022 October 10, about 1 day after the burst. A dedicated analysis of the GRB 221009A data is performed to account for the different moonlight conditions under which data were recorded. We find an excess of gamma-like events with a statistical significance of 4.1σ during the observations taken 1.33 days after the burst, followed by background-compatible results for the later days. The results are compared with various models of afterglows from structured jets that are consistent with the published multiwavelength data but entail significant quantitative and qualitative differences in the VHE emission after 1 day. We disfavor models that imply VHE flux at 1 day considerably above 10−11 erg cm−2 s−1. Our late-time VHE observations can help disentangle the degeneracy among the models and provide valuable new insight into the structure of GRB jets.
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Funding information in the publication:
We gratefully acknowledge financial support from the following agencies and organizations: Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), Fundação de Apoio à Ciência, Tecnologia e Inovação do Paraná–Fundação Araucária, Ministry of Science, Technology, Innovations and Communications (MCTIC), Brasil; Ministry of Education and Science, National RI Roadmap Project DO1-153/28.08.2018, Bulgaria; Croatian Science Foundation (HrZZ) Project IP-2022-10-4595, Rudjer Boskovic Institute, University of Osijek, University of Rijeka, University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Zagreb, Faculty of Electrical Engineering and Computing, Croatia; Ministry of Education, Youth and Sports, MEYS LM2023047, EU/MEYS CZ.02.1.01/0.0/0.0/16_013/0001403, CZ.02.1.01/0.0/0.0/18_046/0016007, CZ.02.1.01/0.0/0.0/16_019/0000754, CZ.02.01.01/00/22_008/0004632, and CZ.02.01.01/00/23_015/0008197 Czech Republic; CNRS-IN2P3, the French Program d’investissements d’avenir and the Enigmass Labex. This work has been done thanks to the facilities offered by the Univ. Savoie Mont Blanc–CNRS/IN2P3 MUST computing center, France; Max Planck Society, German Bundesministerium für Bildung und Forschung (Verbundforschung/ErUM), Deutsche Forschungsgemeinschaft (SFBs 876 and 1491), Germany; Istituto Nazionale di Astrofisica (INAF), Istituto Nazionale di Fisica Nucleare (INFN), Italian Ministry for University and Research (MUR), and the financial support from the European Union–Next Generation EU under the project IR0000012–CTA+ (CUP C53C22000430006), announcement N.3264 on 28/12/2021: “Rafforzamento e creazione di IR nell’ambito del Piano Nazionale di Ripresa e Resilienza (PNRR)”; ICRR, University of Tokyo, JSPS, MEXT, Japan; JST SPRING–JPMJSP2108; Narodowe Centrum Nauki, grant No. 2019/34/E/ST9/00224, Poland. The Spanish groups acknowledge the Spanish Ministry of Science and Innovation and the Spanish Research State Agency (AEI) through the government budget lines PGE2022/28.06.000X.711.04, 28.06.000X.411.01, and 28.06.000X.711.04 of PGE 2023, 2024, and 2025 and grants PID2019-104114RB-C31, PID2019-107847RB-C44, PID2019-104114RB-C32, PID2019-105510GB-C31, PID2019-104114RB-C33, PID2019-107847RB-C43, PID2019-107847RB-C42, PID2019-107988GB-C22, PID2021-124581OB-I00, PID2021-125331NB-I00, PID2022-136828NB-C41, PID2022-137810NB-C22, PID2022-138172NB-C41, PID2022-138172NB-C42, PID2022-138172NB-C43, PID2022-139117NB-C41, PID2022-139117NB-C42, PID2022-139117NB-C43, PID2022-139117NB-C44, PID2022-136828NB-C42, and PDC2023-145839-I00 funded by the Spanish MCIN/AEI/10.13039/501100011033 and by ERDF/EU and NextGenerationEU PRTR; the “Centro de Excelencia Severo Ochoa” program through grant Nos. CEX2019-000920-S, CEX2020-001007-S, CEX2021-001131-S; the “Unidad de Excelencia María de Maeztu” program through grant Nos. CEX2019-000918-M, CEX2020-001058-M; the “Ramón y Cajal” program through grants RYC2021-032991-I funded by MICIN/AEI/10.13039/501100011033 and the European Union “NextGenerationEU”/PRTR and RYC2020-028639-I; the “Juan de la Cierva-Incorporación” program through grant No. IJC2019-040315-I, and “Juan de la Cierva-formación”’ through grant JDC2022-049705-I. They also acknowledge the “Atracción de Talento” program of Comunidad de Madrid through grant No. 2019-T2/TIC-12900; the project “Tecnologías avanzadas para la exploración del universo y sus componentes” (PR47/21 TAU), funded by Comunidad de Madrid, by the Recovery, Transformation and Resilience Plan from the Spanish State, and by NextGenerationEU from the European Union through the Recovery and Resilience Facility; “MAD4SPACE: Desarrollo de tecnologías habilitadoras para estudios del espacio en la Comunidad de Madrid” (TEC-2024/TEC-182) project funded by Comunidad de Madrid; the La Caixa Banking Foundation, grant No. LCF/BQ/PI21/11830030; Junta de Andalucía under Plan Complementario de I+D+I (Ref. AST22_0001) and Plan Andaluz de Investigación, Desarrollo e Innovación as research group FQM-322; project ref. AST22_00001_9 with funding from NextGenerationEU funds; the “Ministerio de Ciencia, Innovación y Universidades” and its “Plan de Recuperación, Transformación y Resiliencia”; “Consejería de Universidad, Investigación e Innovación” of the regional government of Andalucía and “Consejo Superior de Investigaciones Científicas,” grant CNS2023-144504 funded by MICIU/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR, the European Union’s Recovery and Resilience Facility–Next Generation, in the framework of the General Invitation of the Spanish Government’s public business entity Red.es to participate in talent attraction and retention programs within Investment 4 of Component 19 of the Recovery, Transformation and Resilience Plan; Junta de Andalucía under Plan Complementario de I+D+I (Ref. AST22_00001), Plan Andaluz de Investigación, Desarrollo e Innovación (Ref. FQM-322). “Programa Operativo de Crecimiento Inteligente” FEDER 2014-2020 (Ref. ESFRI-2017-IAC-12), Ministerio de Ciencia e Innovación, 15% cofinanced by Consejería de Economía, Industria, Comercio y Conocimiento del Gobierno de Canarias; the “CERCA” program and the grants 2021SGR00426 and 2021SGR00679, all funded by the Generalitat de Catalunya; and the European Union’s NextGenerationEU (PRTR-C17.I1). This research used the computing and storage resources provided by the Port d’Informació Científica (PIC) data center. State Secretariat for Education, Research and Innovation (SERI) and Swiss National Science Foundation (SNSF), Switzerland. The research leading to these results has received funding from the European Union’s Seventh Framework Program (FP7/2007-2013) under grant agreement No. 262053 and No. 317446. This project is receiving funding from the European Union’s Horizon 2020 research and innovation programs under agreement No. 676134. ESCAPE–The European Science Cluster of Astronomy & Particle Physics ESFRI Research Infrastructures has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 824064. In addition, S.I. is supported by MEXT KAKENHI grant No. 23H04896.
