A1 Refereed original research article in a scientific journal
Magnetic-field Order in the Southwestern Rim of RCW 86 Constrained Using X-Ray Polarimetry
Authors: Silvestri, Stefano; Prokhorov, Dmitry; Vink, Jacco; Slane, Patrick; Yang, Yi-Jung; Bucciantini, Niccolo; Ferrazzoli, Riccardo; Zhou, Ping; Costa, Enrico; Omodei, Nicola; Ng, Chi-Yung; Soffitta, Paolo; Weisskopf, Martin C.; Baldini, Luca; Di Marco, Alessandro; Doroshenko, Victor; Heyl, Jeremy; Kaaret, Philip; Marin, Frederic; Mizuno, Tsunefumi; Pesce-Rollins, Melissa; Sgro, Carmelo; Swartz, Douglas A.; Tamagawa, Toru; Xie, Fei; Agudo, Ivan; Antonelli, Lucio A.; Bachetti, Matteo; Baumgartner, Wayne H.; Bellazzini, Ronaldo; Bianchi, Stefano; Bongiorno, Stephen D.; Bonino, Raffaella; Brez, Alessandro; Capitanio, Fiamma; Castellano, Simone; Cavazzuti, Elisabetta; Chen, Chien-Ting; Ciprini, Stefano; De Rosa, Alessandra; Del Monte, Ettore; Di Gesu, Laura; Di Lalla, Niccolo; Donnarumma, Immacolata; Dovciak, Michal; Ehlert, Steven R.; Enoto, Teruaki; Evangelista, Yuri; Fabiani, Sergio; Garcia, Javier A.; Gunji, Shuichi; Hayashida, Kiyoshi; Iwakiri, Wataru; Jorstad, Svetlana G.; Karas, Vladimir; Kislat, Fabian; Kitaguchi, Takao; Kolodziejczak, Jeffery J.; Krawczynski, Henric; La Monaca, Fabio; Latronico, Luca; Liodakis, Ioannis; Maldera, Simone; Manfreda, Alberto; Marinucci, Andrea; Marscher, Alan P.; Marshall, Herman L.; Massaro, Francesco; Matt, Giorgio; Mitsuishi, Ikuyuki; Muleri, Fabio; Negro, Michela; O'dell, Stephen L.; Oppedisano, Chiara; Papitto, Alessandro; Pavlov, George G.; Peirson, Abel L.; Perri, Matteo; Petrucci, Pierre-Olivier; Pilia, Maura; Possenti, Andrea; Poutanen, Juri; Puccetti, Simonetta; Ramsey, Brian D.; Rankin, John; Ratheesh, Ajay; Roberts, Oliver J.; Romani, Roger W.; Spandre, Gloria; Tavecchio, Fabrizio; Taverna, Roberto; Tawara, Yuzuru; Tennant, Allyn F.; Thomas, Nicholas E.; Tombesi, Francesco; Trois, Alessio; Tsygankov, Sergey S.; Turolla, Roberto; Wu, Kinwah; Zane, Silvia
Publisher: Institute of Physics Publishing
Publication year: 2026
Journal: Astrophysical Journal
Article number: 172
Volume: 998
Issue: 1
ISSN: 0004-637X
eISSN: 1538-4357
DOI: https://doi.org/10.3847/1538-4357/ae3004
Publication's open availability at the time of reporting: Open Access
Publication channel's open availability : Open Access publication channel
Web address : https://iopscience.iop.org/article/10.3847/1538-4357/ae3004
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/515863471
Self-archived copy's licence: CC BY
Self-archived copy's version: Publisher`s PDF
RCW 86 is a supernova remnant whose origin has recently been linked to an off-center explosion within a cavity created by its progenitor star. In the southwestern region, the forward shock is thought to have reached the cavity wall, encountering diverse environmental conditions. We report on the spatially resolved X-ray polarimetric observation of RCW 86 with the Imaging X-ray Polarimetry Explorer (IXPE). In the 2–4.5 keV energy band we find no significant detection of polarization. Employing a dedicated background subtraction procedure and Bayesian spectropolarimetric fitting, we derive 99% upper limits on the polarization degree of the synchrotron component: 15% in higher-statistics regions and 30%–40% in lower-statistics regions. These upper limits on the polarization degree in several regions exclude the possibility of a strongly coherent magnetic field down to the subparsec scale, and that of a moderately coherent one on the scale of the synchrotron features as resolved by IXPE. The results indicate that the shocks in the southwestern rim of RCW 86 propagate more slowly than the unshocked ejecta at their locations, yet exceed the measured proper motion speeds. This behavior is consistent with reflected shocks occurring in tenuous regions of the shocked ejecta, distinct from regions that are radio-bright.
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Funding information in the publication:
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-2022-13-I.0, agreements ASI-INAF-2022-19-HH.0 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). R.F., is partially supported by MAECI with grant CN24GR08 “GRBAXP: Guangxi–Rome Bilateral Agreement for X-ray Polarimetry in Astrophysics.” P.Z. acknowledges the support from NSFC grant No. 12273010. F.X. is supported by National Key R&D Program of China (grant No. 2023YFE0117200), and National Natural Science Foundation of China (grant Nos. 12373041 and 12422306), and Bagui Scholars Program (XF). C.-Y.N. is supported by a GRF grant of the Hong Kong Government under HKU 17304524. I.L was funded by the European Union ERC-2022-STG – BOOTES – 101076343. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them.
