Early photometric and spectroscopic observations of the extraordinarily bright INTEGRAL-detected GRB 221009A

¹ Instituto de Astrofísica de Andalucía, Consejo Superior de Investigaciones Científicas (IAA-CSIC), Glorieta de la Astronomía, s/n, 18080 Granada, Spain
² Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Nikolaus-Fiebiger-Str. 2, Erlangen D-91058, Germany
³ Space Research Institute, Russian Academy of Sciences, Profsoyuznaya, 84/32, Moscow 117997, Russia
⁴ Higher School of Economics, National Research University, Myasnitskaya 20, Moscow 101000, Russia
⁵ Moscow Institute of Physics and Technology (MIPT), Institutskiy Pereulok, 9, Dolgoprudny 141701, Russia
⁶ Departamento de Física y Matemáticas, Universidad de Monterrey, Avda. Morones Prieto 4500, San Pedro Garza García, 66238 Nuevo León, Mexico
⁷ Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital, 263002 Uttarakhand, India
⁸ Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771, USA
⁹ NASA Postdoctoral Program Fellow, Greenbelt, MD 20771, USA
¹⁰ School of Astronomy and Space Science, Nanjing University, Nanjing 210093, China
¹¹ Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, China
¹² School of Physics and Astronomy & Institute for Gravitational Wave Astronomy, University of Birmingham, Birmingham B15 2TT, UK
¹³ Petro Mohyla Black Sea National University, 68 Desantnykiv Street, 10, Mykolaiv 54003, Ukraine
¹⁴ Laboratório Nacional de Astrofísica, Itajubá, MG, Brazil
¹⁵ Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, Rio de Janeiro, 22290-180 RJ, Brazil
¹⁶ Centro Federal de Educação Tecnológica Celso Suckow da Fonseca, Rodovia Mário Covas, lote J2, quadra J, Itaguaí, 23810-000 RJ, Brazil
¹⁷ East Tennessee State University, 1276 Gilbreath Dr., Box 70300 Johnson City, 37614 TN, USA
¹⁸ Ulugh Beg Astronomical Institute, Uzbek Academy of Sciences, Tashkent, Uzbekistan
¹⁹ Unidad Asociada al CSIC, Dpto. de Ingeniería de Sistemas y Automática, Escuela de Ingenierías, Universidad de Málaga, C/ Dr. Ortiz Ramos, s/n, Málaga 29071, Spain
²⁰ Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, Evanston, 60208 IL, USA
²¹ Institute of Solar-Terrestrial Physics, Russian Academy of Sciences, Siberian Branch, Irkutsk, Russia
²² International Center for Advanced Studies & Instituto de Ciencias Físicas, ECyT-UNSAM & CONICET, Buenos Aires 1650, Argentina
²³ Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnii Arkhyz 369167, Russia
²⁴ SOAR Telescope, NSF’s NOIRLab, Avda. Juan Cisternas, 1500, La Serena 1700000, Chile
²⁵ Austin Peay State University, 601 College St, Clarksville, 37044 TN, USA
²⁶ Department of Astronomy and Astrophysics, University of California, Santa Cruz, 95064 CA, USA
²⁷ Fermi National Accelerator Laboratory, P. O. Box 500 Batavia, 60510 IL, USA
²⁸ Benedictine University, 5700 College Road, Lisle, IL, USA
²⁹ Swedish Institute of Space Physics (IRF), Bengt Hultqvists väg 1, 981 92 Kiruna, Sweden
³⁰ Faculty of Science, University of Helsinki, Gustaf Hallströmin katu 2, FI-00014 Helsinki, Finland
³¹ Institute of Physics and Technology, Ural Federal University, Mira str. 19, 620002 Ekaterinburg, Russia
³² Department of Applied Physics/Physics, Mahatma Jyotiba Phule Rohilkhand University, Bareilly-243006, India
³³ Petrozavodsk State University, Petrozavodsk, Russia
³⁴ School of Physics & Astronomy, Monash University, Clayton, VIC 3800, Australia
³⁵ INAF - Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate (LC), Italy

^⋆ Corresponding authors; ruben.sanchez@csic.es, amitror@aries.res.in

Received: 28 February 2024
Accepted: 5 September 2024

Abstract

Context. GRB 221009A, initially detected as an X-ray transient by Swift, was later revealed to have triggered the Fermi satellite about an hour earlier, marking it as a post-peak observation of the event’s emission. This GRB distinguished itself as the brightest ever recorded, presenting an unparalleled opportunity to probe the complexities of GRB physics. The unprecedented brightness, however, challenged observation efforts, as it led to the saturation of several high-energy instruments.

Aims. Our study seeks to investigate the nature of the INTEGRAL-detected GRB 221009A and elucidate the environmental conditions conducive to these exceptionally powerful bursts. Moreover, we aim to understand the fundamental physics illuminated by the detection of teraelectronvolt (TeV) photons emitted by GRB 221009A.

Methods. We conducted detailed analyses of early photometric and spectroscopic observations that span from the Fermi trigger through to the initial days following the prompt emission phase in order to characterize GRB 221009A’s afterglow, and we complemented these analyses with a comparative study.

Results. Our findings from analyzing INTEGRAL data confirm GRB 221009A as the most energetic event observed to date. Early optical observations during the prompt phase negate the presence of bright optical emissions with internal or external shock origins. Spectroscopic analyses enabled us to measure GRB 221009A’s distance and line-of-sight properties. The afterglow’s temporal and spectral analysis suggests prolonged activity of the central engine and a transition in the circumburst medium’s density. Finally, we discuss the implications for fundamental physics of detecting photons as energetic as 18 TeV from GRB 221009A.

Conclusions. Early optical observations have proven invaluable for distinguishing between the potential origins of optical emissions in GRB 221009A, underscoring their utility in GRB physics studies. However, the rarity of such data underscores the need for dedicated telescopes capable of synchronous multiwavelength observations. Additionally, our analysis suggests that the host galaxies of TeV GRBs share commonalities with those of long and short GRBs. Expanding the sample of TeV GRBs could further solidify these findings.