Magnetic-field Order in the Southwestern Rim of RCW 86 Constrained Using X-Ray Polarimetry

Abstract 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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Publication Details

Journal
The Astrophysical Journal
Published
2026-02-09
DOI
https://doi.org/10.3847/1538-4357/ae3004
Primary Topic
Astrophysics and Cosmic Phenomena
Type
article
Field-Weighted Citation Impact
0.00

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article

Magnetic-field Order in the Southwestern Rim of RCW 86 Constrained Using X-Ray Polarimetry

Chi-yung Ng, Laura Di Gesu, Ioannis Liodakis, C. Chen et al.
The Astrophysical Journal
Astrophysics and Cosmic Phenomena
article

Magnetic-field Order in the Southwestern Rim of RCW 86 Constrained Using X-Ray Polarimetry

Chi-yung Ng, Laura Di Gesu, Ioannis Liodakis, C. Chen, F. La Monaca, Abel L. Peirson, Stefano Silvestri, Vladimir Karas, B. Ramsey, Fabian Kislat, Andrea Marinucci, Matteo Bachetti, Silvia Zane, Roberto Taverna, Matteo Perri, Yuzuru Tawara, T. Kitaguchi, Jeremy Heyl, Ivan Agudo, Patrick Slane, Niccolò Di Lalla, Maura Pilia, John Rankin, Ajay Ratheesh, Alessio Trois, Luca Latronico, Fiamma Capitanio, Luca Baldini, Nicola Omodei, Gloria Spandre, Alessandro Brez, Simone Maldera, Henric Krawczynski, Douglas A. Swartz, Ettore Del Monte, Tsunefumi Mizuno, Raffaella Bonino, Roberto Turolla, Ikuyuki Mitsuishi, Nicholas E. Thomas, Wataru Iwakiri, Andrea Possenti, Stephen L. O’Dell, Michal Dovčiak, Niccolò Bucciantini, Javier A. García, Simone Castellano, Jacco Vink, Wayne H. Baumgartner, Pierre-Olivier Petrucci, Teruaki Enoto, Fabio Muleri, Jeffery J. Kolodziejczak, Alessandro Papitto, Stephen D. Bongiorno, George G. Pavlov, Allyn F. Tennant, Ronaldo Bellazzini, Shuichi Gunji, Martin C. Weisskopf, Kinwah Wu, Toru Tamagawa, Alessandra De Rosa, Yi-Jung Yang, Chiara Oppedisano, Fei Xie, Elisabetta Cavazzuti, Francesco Tombesi, Frédéric Marin, Roger W. Romani, Svetlana G. Jorstad, Riccardo Ferrazzoli, Sergey S. Tsygankov, Steven R. Ehlert, Stefano Bianchi, Simonetta Puccetti, Enrico Costa, Melissa Pesce-Rollins, Francesco Massaro, Giorgio Matt, Sergio Fabiani, Dmitry Prokhorov, Fabrizio Tavecchio, Herman L. Marshall, Alessandro Di Marco, Kiyoshi Hayashida, Immacolata Donnarumma, Paolo Soffitta, Alan P. Marscher, Oliver J. Roberts, Philip Kaaret, Stefano Ciprini, Ping Zhou, Lucio A. Antonelli
article en

Abstract

Abstract 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.

The Astrophysical JournalVol. 998(1)
National Aeronautics and Space Administration, European Commission, National Natural Science Foundation of China, Agenzia Spaziale Italiana, Istituto Nazionale di Astrofisica, Ministero degli Affari Esteri e della Cooperazione Internazionale, Istituto Nazionale di Fisica Nucleare, Hong Kong Government, Marshall Space Flight Center, Goddard Space Flight Center
Openalex Percentile: Top 58%
Astrophysics and Cosmic Phenomena
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