H.E.S.S. follow-up observations of GRB221009A
Creators: name: Collaboration, H. E. S. S.
name: :
name: Aharonian, F.
name: Benkhali, F. Ait
name: Aschersleben, J.
name: Ashkar, H.
name: Backes, M.
name: Baktash, A.
name: Martins, V. Barbosa
name: Batzofin, R.
name: Becherini, Y.
name: Berge, D.
name: Bernlöhr, K.
name: Bi, B.
name: Böttcher, M.
name: Boisson, C.
name: Bolmont, J.
name: de Lavergne, M. de Bony
name: Borowska, J.
name: Bouyahiaoui, M.
name: Bradascio, F.
name: Breuhaus, M.
name: Brose, R.
name: Brun, F.
name: Bruno, B.
name: Bulik, T.
name: Burger-Scheidlin, C.
name: Caroff, S.
name: Casanova, S.
name: Celic, J.
name: Cerruti, M.
name: Chand, T.
name: Chandra, S.
name: Chen, A.
name: Chibueze, J.
name: Chibueze, O.
name: Cotter, G.
name: Dai, S.
name: Mbarubucyeye, J. Damascene
name: Devin, J.
name: Djannati-Ataï, A.
name: Dmytriiev, A.
name: Doroshenko, V.
name: Egberts, K.
name: Einecke, S.
name: Ernenwein, J. -P.
name: Fegan, S.
name: de Clairfontaine, G. Fichet
name: Filipovic, M.
name: Fontaine, G.
name: Füßling, M.
name: Funk, S.
name: Gabici, S.
name: Ghafourizadeh, S.
name: Giavitto, G.
name: Glawion, D.
name: Glicenstein, J. F.
name: Goswami, P.
name: Grolleron, G.
name: Hinton, M. -H. Grondin J. A.
name: Holch, T. L.
name: Holler, M.
name: Horns, D.
name: Huang, Zhiqiu
name: Jamrozy, M.
name: Jankowsky, F.
name: Joshi, V.
name: Jung-Richardt, I.
name: Kasai, E.
name: Katarzyński, K.
name: Khatoon, R.
name: Khélifi, B.
name: Kluźniak, W.
name: Komin, Nu.
name: Konno, R.
name: Kosack, K.
name: Kostunin, D.
name: Lang, R. G.
name: Stum, S. Le
name: Leitl, F.
name: Lemière, A.
name: Lemoine-Goumard, M.
name: Lenain, J. P.
name: Leuschner, F.
name: Lohse, T.
name: Lypova, I.
name: Mackey, J.
name: Malyshev, D.
name: Malyshev, D.
name: Marandon, V.
name: Marchegiani, P.
name: Marcowith, A.
name: Martí-Devesa, G.
name: Marx, R.
name: Meyer, M.
name: Mitchell, A.
name: Mohrmann, L.
name: Montanari, A.
name: Moulin, E.
name: Murach, T.
name: Nakashima, K.
name: de Naurois, M.
name: Niemiec, J.
name: Noel, A. Priyana
name: O'Brien, P.
name: Ohm, S.
name: Olivera-Nieto, L.
name: Wilhelmi, E. de Ona
name: Ostrowski, M.
name: Panny, S.
name: Panter, M.
name: Parsons, R. D.
name: Peron, G.
name: Prokhorov, D. A.
name: Prokoph, H.
name: Pühlhofer, G.
name: Punch, M.
name: Quirrenbach, A.
name: Reichherzer, P.
name: Reimer, A.
name: Reimer, O.
name: Ren, H.
name: Renaud, M.
name: Reville, B.
name: Rieger, F.
name: Rowell, G.
name: Rudak, B.
name: Ruiz-Velasco, E.
name: Sahakian, V.
name: Salzmann, H.
name: Santangelo, A.
name: Sasaki, M.
name: Schäfer, J.
name: Schüssler, F.
name: Schutte, H. M.
name: Schwanke, U.
name: Shapopi, J. N. S.
name: Specovius, A.
name: Spencer, S.
name: Stawarz, Ł.
name: Steenkamp, R.
name: Steinmassl, S.
name: Steppa, C.
name: Sushch, I.
name: Suzuki, H.
name: Takahashi, T.
name: Tanaka, T.
name: Terrier, R.
name: Tsuji, N.
name: Uchiyama, Y.
name: Vecchi, M.
name: Venter, C.
name: Vink, J.
name: Wagner, S. J.
name: White, R.
name: Wierzcholska, A.
name: Wong, Yu Wun
name: Zacharias, M.
name: Zargaryan, D.
name: Zdziarski, A. A.
name: Zech, A.
name: Zhu, S. J.
name: Żywucka, N.
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: GRB221009A is the brightest gamma-ray burst ever detected. To probe the very-high-energy (VHE, $&gt;$\!100 GeV) emission, the High Energy Stereoscopic System (H.E.S.S.) began observations 53 hours after the triggering event, when the brightness of the moonlight no longer precluded observations. We derive differential and integral upper limits using H.E.S.S. data from the third, fourth, and ninth nights after the initial GRB detection, after applying atmospheric corrections. The combined observations yield an integral energy flux upper limit of $Φ_\mathrm{UL}^{95\%} = 9.7 \times 10^{-12}~\mathrm{erg\,cm^{-2}\,s^{-1}}$ above $E_\mathrm{thr} = 650$ GeV. The constraints derived from the H.E.S.S. observations complement the available multiwavelength data. The radio to X-ray data are consistent with synchrotron emission from a single electron population, with the peak in the SED occurring above the X-ray band. Compared to the VHE-bright GRB190829A, the upper limits for GRB221009A imply a smaller gamma-ray to X-ray flux ratio in the afterglow. Even in the absence of a detection, the H.E.S.S. upper limits thus contribute to the multiwavelength picture of GRB221009A, effectively ruling out an IC dominated scenario.
description: 10 pages, 4 figures. Accepted for publication in APJL. Corresponding authors: J. Damascene Mbarubucyeye, H. Ashkar, S. J. Zhu, B. Reville, F. Sch\"ussler