Issue |
A&A
Volume 677, September 2023
|
|
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Article Number | L2 | |
Number of page(s) | 7 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202346128 | |
Published online | 29 August 2023 |
Letter to the Editor
The peak flux of GRB 221009A measured with GRBAlpha
1
Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotlářská 267/2, Brno 611 37, Czech Republic
e-mail: ripa.jakub@gmail.com
2
Department of Physics, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, Japan
3
Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Budapest, Hungary
4
Eötvös Loránd University, Egyetem tér 1-3, Budapest, Hungary
5
Wigner Research Centre for Physics, Konkoly-Thege Miklós út 29-33, Budapest, Hungary
6
Spacemanic Ltd, Jablonec 110, 900 86 Jablonec, Slovakia
7
Needronix Ltd, Ilkovičová 3, 812 19 Bratislava, Slovakia
8
EDIS vvd., 04001 Košice, Slovakia
9
Faculty of Aeronautics, Technical University of Košice, Košice, Slovakia
10
Department of Radio Electronics, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic
11
Tokyo University of Science, Noda, Chiba, Japan
12
Department of Physics, Nagoya University, Nagoya, Aichi, Japan
13
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa, Japan
14
Institute of Earth Physics and Space Science (EPSS), Csatkai E. u. 6-8., 9400 Sopron, Hungary
15
Department of Physics and Astronomy, Universiteit Gent, 9000 Ghent, Belgium
16
School of Science, Kyoto University, Kyoto, Japan
17
Department of Physics, Rikkyo University, Tokyo, Japan
18
Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3, 1111 Budapest, Hungary
19
MTA-BME Quantum Dynamics and Correlations Research Group, Budapest University of Technology and Economics, Műegyetem rkp. 3, 1111 Budapest, Hungary
20
Department of Earth and Space Science, Osaka University, Toyonaka, Osaka, Japan
21
INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica, Via A. Corti 12, 20133 Milano, Italy
Received:
12
February
2023
Accepted:
14
March
2023
Context. On 2022 October 9 the brightest gamma-ray burst (GRB) ever observed lit up the high-energy sky. It was detected by a multitude of instruments, attracting the close attention of the GRB community, and saturated many detectors.
Aims. GRBAlpha, a nano-satellite with a form factor of a 1U CubeSat, detected this extraordinarily bright long-duration GRB, GRB 221009A, without saturation but affected by pile-up. We present light curves of the prompt emission in 13 energy bands, from 80 keV to 950 keV, and performed a spectral analysis to calculate the peak flux and peak isotropic-equivalent luminosity.
Methods. Since the satellite’s attitude information is not available for the time of this GRB, more than 200 incident directions were probed in order to find the median luminosity and its systematic uncertainty.
Results. We find that the peak flux in the 80 − 800 keV range (observer frame) was Fphp = 1300−200+1200 ph cm−2 s−1, or Fergp = 5.7−0.7+3.7 × 10−4 erg cm−2 s−1, and the fluence in the same energy range of the first GRB episode, which lasted 300 s and was observable by GRBAlpha, was S = 2.2−0.3+1.4 × 10−2 erg cm−2, or Sbol = 4.9−0.5+0.8 × 10−2 erg cm−2 for the extrapolated range of 0.9 − 8690 keV. We infer the isotropic-equivalent released energy of the first GRB episode to be Eisobol = 2.8−0.5+0.8 × 1054 erg in the 1 − 10 000 keV band (rest frame at z = 0.15). The peak isotropic-equivalent luminosity in the 92 − 920 keV range (rest frame) was Lisop = 3.7−0.5+2.5 × 1052 erg s−1, and the bolometric peak isotropic-equivalent luminosity was Lisop,bol = 8.4−1.5+2.5 × 1052 erg s−1 (4 s scale) in the 1 − 10 000 keV range (rest frame). The peak emitted energy is Ep∗ = Ep(1+z) = 1120 ± 470 keV. Our measurement of Lisop,bol is consistent with the Yonetoku relation. It is possible that, due to the spectral evolution of this GRB and the orientation of GRBAlpha at the peak time, the true values of peak flux, fluence, Liso, and Eiso are even higher.
Key words: gamma-ray burst: individual: GRB 221009A
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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