The IXPE view of GRB 221009A
Creators: name: Negro, Michela
name: Di Lalla, Niccoló
name: Omodei, Nicola
name: Veres, Péter
name: Silvestri, Stefano
name: Manfreda, Alberto
name: Burns, Eric
name: Baldini, Luca
name: Costa, Enrico
name: Ehlert, Steven R.
name: Kennea, Jamie A.
name: Liodakis, Ioannis
name: Marshall, Herman L.
name: Mereghetti, Sandro
name: Middei, Riccardo
name: Muleri, Fabio
name: O'Dell, Stephen L.
name: Roberts, Oliver J.
name: Romani, Roger W.
name: Sgró, Carmelo
name: Di Marco, Alessandro
name: Puccetti, Simonetta
name: Terashima, Masanobu
name: Tiengo, Andrea
name: Viscolo, Domenico
name: La Monaca, Fabio
name: Latronico, Luca
name: Matt, Giorgio
name: Perri, Matteo
name: Poutanen, Juri
name: Ratheesh, Ajay
name: Rogantini, Daniele
name: Slane, Patrick
name: Soffitta, Paolo
name: Lindfors, Elina
name: Nilsson, Kari
name: Kasikov, Anni
name: Marscher, Alan P.
name: Tavecchio, Fabrizio
name: Gunji, Shuichi
name: Malacaria, Christian
name: Paggi, Alessandro
name: Yang, Yi-Jung
name: Zane, Silvia
name: Weisskopf, Martin C.
name: Agudo, Iván
name: Antonelli, Lucio A.
name: Baumgartner, Wayne H.
name: Bellazzini, Ronaldo
name: Bianchi, Stefano
name: Bonino, Raffaella
name: Brez, Alessandro
name: Bucciantini, Niccol
name: Castellano, Simone
name: Cavazzuti, Elisabetta
name: Chen, Chien-Ting
name: De Rosa, Alessandra
name: Del Monte, Ettore
name: Di Gesu, Laura
name: Donnarumma, Immacolata
name: Doroshenko, Victor
name: Dovciak, Michal
name: Enoto, Teruaki
name: Bachetti, Matteo
name: Bongiorno, Stephen D.
name: Capitanio, Fiamma
name: Ciprini, Stefano
name: Evangelista, Yuri
name: Fabiani, Sergio
name: Ferrazzoli, Riccardo
name: Garcia, Javier A.
name: Hayashida, Kiyoshi
name: Heyl, Jeremy
name: Iwakiri, Wataru
name: Jorstad, Svetlana G.
name: Kaaret, Philip
name: Karas, Vladimir
name: Kislat, Fabian
name: Kitaguchi, Takao
name: Kolodziejczak, Jeffery J.
name: Krawczynski, Henric
name: Maldera, Simone
name: Marin, Frédéric
name: Marinucci, Andrea
name: Mitsuishi, Ikuyuki
name: Mizuno, Tsunefumi
name: Ng, C. -Y.
name: Oppedisano, Chiara
name: Papitto, Alessandro
name: Pavlov, George G.
name: Peirson, Abel L.
name: Pesce-Rollins, Melissa
name: Petrucci, Pierre-Olivier
name: Ramsey, Brian D.
name: Rankin, John
name: Spandre, Gloria
name: Pilia, Maura
name: Possenti, Andrea
name: Swartz, Douglas A.
name: Tamagawa, Toru
name: Taverna, Roberto
name: Tawara, Yuzuru
name: Tennant, Allyn F.
name: Thomas, Nicholas E.
name: Tombesi, Francesco
name: Trois, Alessio
name: Tsygankov, Sergey S.
name: Turolla, Roberto
name: Vink, Jacco
name: Wu, Kinwah
name: Xie, Fei
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present the IXPE observation of GRB 221009A which includes upper limits on the linear polarization degree of both prompt and afterglow emission in the soft X-ray energy band. GRB 221009A is an exceptionally bright gamma-ray burst (GRB) that reached Earth on 2022 October 9 after travelling through the dust of the Milky Way. The Imaging X-ray Polarimetry Explorer (IXPE) pointed at GRB 221009A on October 11 to observe, for the first time, the 2-8 keV X-ray polarization of a GRB afterglow. We set an upper limit to the polarization degree of the afterglow emission of 13.8% at a 99% confidence level. This result provides constraints on the jet opening angle and the viewing angle of the GRB, or alternatively, other properties of the emission region. Additionally, IXPE captured halo-rings of dust-scattered photons which are echoes of the GRB prompt emission. The 99% confidence level upper limit to the prompt polarization degree depends on the background model assumption and it ranges between ~55% to ~82%. This single IXPE pointing provides both the first assessment of X-ray polarization of a GRB afterglow and the first GRB study with polarization observations of both the prompt and afterglow phases.
description: Accepted by Astrophysical Journal Letters