The IXPE View of GRB 221009A

Michela Negro , Niccolò Di Lalla , Nicola Omodei , Péter Veres , Stefano Silvestri , Alberto Manfreda , Eric Burns , Luca Baldini , Enrico Costa , Steven R. Ehlert , Jamie A. Kennea , Ioannis Liodakis , Herman L. Marshall , Sandro Mereghetti , Riccardo Middei , Fabio Muleri , Stephen L. O'Dell , Oliver J. Roberts , Roger W. Romani , Carmelo Sgró , Masanobu Terashima , Andrea Tiengo , Domenico Viscolo , Alessandro Di Marco , Fabio La Monaca , Luca Latronico , Giorgio Matt , Matteo Perri , Simonetta Puccetti , Juri Poutanen , Ajay Ratheesh , Daniele Rogantini , Patrick Slane , Paolo Soffitta , Elina Lindfors , Kari Nilsson , Anni Kasikov , Alan P. Marscher , Fabrizio Tavecchio , Nicoló Cibrario , Shuichi Gunji , Christian Malacaria , Alessandro Paggi , Yi-Jung Yang , Silvia Zane , Martin C. Weisskopf , Iván Agudo , Lucio A. Antonelli , Matteo Bachetti , Wayne H. Baumgartner , Ronaldo Bellazzini , Stefano Bianchi , Stephen D. Bongiorno , Raffaella Bonino , Alessandro Brez , Niccolò Bucciantini , Fiamma Capitanio , Simone Castellano , Elisabetta Cavazzuti , Chien-Ting Chen , Stefano Ciprini , Alessandra de Rosa , Ettore del Monte , Laura Di Gesu , Immacolata Donnarumma , Victor Doroshenko , Michal Dovc̆iak , Teruaki Enoto , Yuri Evangelista , Sergio Fabiani , Riccardo Ferrazzoli , Javier A. Garcia , Kiyoshi Hayashida , Jeremy Heyl , Wataru Iwakiri , Svetlana G. Jorstad , Philip Kaaret , Vladimir Karas , Fabian Kislat , Takao Kitaguchi , Jeffery J. Kolodziejczak , Henric Krawczynski , Simone Maldera , Frédéric Marin (1) , Andrea Marinucci , Ikuyuki Mitsuishi , Tsunefumi Mizuno , C. -Y. Ng , Chiara Oppedisano , Alessandro Papitto , George G. Pavlov , Abel L. Peirson , Melissa Pesce-Rollins , Pierre-Olivier Petrucci (2) , Maura Pilia , Andrea Possenti , Brian D. Ramsey , John Rankin , Gloria Spandre , Douglas A. Swartz , Toru Tamagawa , Roberto Taverna , Yuzuru Tawara , Allyn F. Tennant , Nicholas E. Thomas , Francesco Tombesi , Alessio Trois , Sergey S. Tsygankov , Roberto Turolla , Jacco Vink , Kinwah Wu , Fei Xie

1 ObAS - Observatoire astronomique de Strasbourg
2 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

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 traveling 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 that 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% and ~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.

Keywords: Gamma-ray bursts; Polarimetry; X-ray astronomy; 629; 1278; 1810

Domains: Sciences of the Universe [physics]

Michela Negro, Niccolò Di Lalla, Nicola Omodei, Péter Veres, Stefano Silvestri, et al.. The IXPE View of GRB 221009A. The Astrophysical Journal Letters, 2023, 946, ⟨10.3847/2041-8213/acba17⟩. ⟨insu-04056594⟩