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Published March 1, 2023 | Published
Journal Article Open

The IXPE View of GRB 221009A

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


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.

Additional Information

© 2023. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Focus on the Ultra-luminous Gamma-Ray Burst GRB 221009A We thank Hintz Amenitsch for fruitful discussions on X-ray scattering at small angles. We also thank Joe Bright for pointing out a miscalculation of the k parameter in an earlier version of this paper. A special acknowledgement goes to developers of the Slack teamwork platform, which played a crucial role in enabling fast and efficient communication among several different teams. We thank I. Negueruela for the careful optical polarization observations at the Nordic Optical Telescope. This work is based on observations made with the Nordic Optical Telescope (NOT), owned in collaboration by the University of Turku and Aarhus University, and operated jointly by Aarhus University, the University of Turku and the University of Oslo, representing Denmark, Finland, and Norway, the University of Iceland and Stockholm University at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofísica de Canarias. The data presented here were obtained with ALFOSC, which is provided by the Instituto de Astrofísica de Andalucía (IAA) under a joint agreement with the University of Copenhagen and NOT. M.N. acknowledges the support by NASA under award number 80GSFC21M0002. P.V. acknowledges support from NASA grant NNM11AA01A. IXPE-related research at Boston University is supported in part by U.S. National Science Foundation grant AST-2108622. S.M. and A.T. acknowledge financial support from the Italian MUR through grant PRIN 2017LJ39LM. The Imaging X-ray Polarimetry Explorer (IXPE) is a joint US and Italian mission. The US contribution is supported by the National Aeronautics and Space Administration (NASA) and led and managed by its Marshall Space Flight Center (MSFC), with industry partner Ball Aerospace (contract NNM15AA18C). The Italian contribution is supported by the Italian Space Agency (Agenzia Spaziale Italiana, ASI) through contract ASI-OHBI-2017-12-I.0, agreements ASI-INAF-2017-12-H0 and ASI-INFN-2017.13-H0, and its Space Science Data Center (SSDC) with agreements ASI-INAF-2022-14-HH.0 and ASI-INFN 2021-43-HH.0, and by the Istituto Nazionale di Astrofisica (INAF) and the Istituto Nazionale di Fisica Nucleare (INFN) in Italy. This research used data products provided by the IXPE Team (MSFC, SSDC, INAF, and INFN) and distributed with additional software tools by the High-Energy Astrophysics Science Archive Research Center (HEASARC), at NASA Goddard Space Flight Center (GSFC).

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August 22, 2023
October 20, 2023