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X-ray polarization detection of Cassiopeia A with IXPE

Authors :
Vink, Jacco
Prokhorov, Dmitry
Ferrazzoli, Riccardo
Slane, Patrick
Zhou, Ping
Asakura, Kazunori
Baldini, Luca
Bucciantini, Niccolo
Costa, Enrico
Di Marco, Alessandro
Heyl, Jeremy
Marin, Frederic
Mizuno, Tsunefumi
Ng, C. Y.
Pesce-Rollins, Melissa
Ramsey, Brian D.
Rankin, John
Ratheesh, Ajay
Sgro, Carmelo
Soffitta, Paolo
Swartz, Douglas A.
Tamagawa, Toru
Weisskopf, Martin C.
Yang, Yi-Jung
Bellazzini, Ronaldo
Bonino, Raffaella
Cavazzuti, Elisabetta
Costamante, Luigi
Di Lalla, Niccolo
Latronico, Luca
Maldera, Simone
Manfreda, Alberto
Massaro, Francesco
Mitsuishi, Ikuyuki
Omodei, Nicola
Oppedisano, Chiara
Zane, Silvia
Agudo, Ivan
Antonelli, Lucio A.
Bachetti, Matteo
Baumgartner, Wayne H.
Bianchi, Stefano
Bongiorno, Stephen D.
Brez, Alessandro
Capitanio, Fiamma
Castellano, Simone
Ciprini, Stefano
De Rosa, Alessandra
Del Monte, Ettore
Di Gesu, Laura
Donnarumma, Immacolata
Doroshenko, Victor
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
Kitaguchi, Takao
Kolodziejczak, Jeffery J.
Krawczynski, Henric
La Monaca, Fabio
Liodakis, Ioannis
Marinucci, Andrea
Marscher, Alan P.
Marshall, Herman L.
Matt, Giorgio
Muleri, Fabio
O'Dell, Stephen L.
Papitto, Alessandro
Pavlov, George G.
Peirson, Abel L.
Perri, Matteo
Pilia, Maura
Possenti, Andrea
Poutanen, Juri
Puccetti, Simonetta
Romani, Roger W.
Spandre, Gloria
Tavecchio, Fabrizio
Taverna, Roberto
Tawara, Yuzuru
Tennant, Allyn F.
Thomas, Nicolas E.
Tombesi, Francesco
Trois, Alessio
Tsygankov, Sergey
Turolla, Roberto
Wu, Kinwah
Xie, Fei
Publication Year :
2022

Abstract

We report on a $\sim 5\sigma$ detection of polarized 3-6 keV X-ray emission from the supernova remnant Cassiopeia A with the Imaging X-ray Polarimetry Explorer (IXPE). The overall polarization degree of $1.8 \pm 0.3$% is detected by summing over a large region, assuming circular symmetry for the polarization vectors. The measurements imply an average polarization degree for the synchrotron component of $\sim 2.5$%, and close to 5% for the X-ray synchrotron-domimated forward-shock region. These numbers are based on an assessment of the thermal and non-thermal radiation contributions, for which we used a detailed spatial-spectral model based on Chandra X-ray data. A pixel-by-pixel search for polarization provides a few tentative detections from discrete regions at the $\sim 3\sigma$ confidence level. Given the number of pixels, the significance is {insufficient} to claim a detection for individual pixels, but implies considerable turbulence on scales smaller than the angular resolution. Cas A's X-ray continuum emission is dominated by synchrotron radiation from regions within $\lesssim 10^{17}$ cm of the forward- and reverse shocks. We find that i) the measured polarization angle corresponds to a radially-oriented magnetic field, similar to what has been inferred from radio observations; ii) the X-ray polarization degree is lower than in the radio band ($\sim 5$%). Since shock compression should impose a tangential magnetic field structure, the IXPE results imply that magnetic-fields are reoriented within $\sim 10^{17}$cm of the shock. If the magnetic-field alignment is due to locally enhanced acceleration near quasi-parallel shocks, the preferred X-ray polarization angle suggests a size of $3\times 10^{16}$ cm for cells with radial magnetic fields.<br />Comment: IXPE collaboration paper. Accepted by the Astrophysical Journal. This version reflects the version accepted by ApJ. With respect to version 1: new figures added to the Appendix and extension to the text, in particular the discussion section and Appendix

Details

Database :
arXiv
Publication Type :
Report
Accession number :
edsarx.2206.06713
Document Type :
Working Paper
Full Text :
https://doi.org/10.3847/1538-4357/ac8b7b