arXiv · 2304.00925
A polarimetrically oriented X-ray stare at the accreting pulsar EXO 2030+375
Abstract
Accreting X-ray pulsars (XRPs) are presumably ideal targets for polarization measurements, as their high magnetic field strength is expected to polarize the emission up to a polarization degree of ~80%. However, such expectations are being challenged by recent observations of XRPs with the Imaging X-ray Polarimeter Explorer (IXPE). Here we report on the results of yet another XRP, EXO 2030+375, observed with IXPE and contemporarily monitored with Insight-HXMT and SRG/ART-XC. In line with recent results obtained with IXPE for similar sources, analysis of the EXO 2030+375 data returns a low polarization degree of 0%-3% in the phase-averaged study and variation in the range 2%-7% in the phase-resolved study. Using the rotating vector model we constrain the geometry of the system and obtain a value for the magnetic obliquity of ~$60^{\circ}$. Considering also the estimated pulsar inclination of ~$130^{\circ}$, this indicates that the magnetic axis swings close to the observer line of sight. Our joint polarimetric, spectral and timing analysis hint to a complex accreting geometry where magnetic multipoles with asymmetric topology and gravitational light bending significantly affect the observed source behavior.
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Christian Malacaria, Jeremy Heyl, Victor Doroshenko, Sergey S. Tsygankov, Juri Poutanen, Sofia V. Forsblom, Fiamma Capitanio, Alessandro Di Marco, Yujia Du, Lorenzo Ducci, Fabio La Monaca, Alexander A. Lutovinov, Herman L. Marshall, Ilya A. Mereminskiy, Sergey V. Molkov, Mason Ng, Pierre-Olivier Petrucci, Andrea Santangelo, Andrey E. Shtykovsky, Valery F. Suleimanov, Ivan Agudo, Lucio A. Antonelli, Matteo Bachetti, Luca Baldini, Wayne H. Baumgartner, Ronaldo Bellazzini, Stefano Bianchi, Stephen D. Bongiorno, Raffaella Bonino, Alessandro Brez, Niccolo Bucciantini, Simone Castellano, Elisabetta Cavazzuti, Chien-Ting Chen, Stefano Ciprini, Enrico Costa, Alessandra De Rosa, Ettore Del Monte, Laura Di Gesu, Niccolo Di Lalla, Immacolata Donnarumma, Michal Dovciak, Steven R. Ehlert, Teruaki Enoto, Yuri Evangelista, Sergio Fabiani, Riccardo Ferrazzoli, Javier A. Garcia, Shuichi Gunji, Kiyoshi Hayashida, Wataru Iwakiri, Svetlana G. Jorstad, Philip Kaaret, Vladimir Karas, Fabian Kislat, Takao Kitaguchi, Jeffery J. Kolodziejczak1, Henric Krawczynski, Luca Latronico, Ioannis Liodakis, Simone Maldera, Alberto Manfreda, Frederic Marin, Andrea Marinucci, Alan P. Marscher, Francesco Massaro, Giorgio Matt, Ikuyuki Mitsuishi, Tsunefumi Mizuno, Fabio Muleri, Michela Negro, Chi-Yung Ng, Stephen L. O'Dell, Nicola Omodei, Chiara Oppedisano, Alessandro Papitto, George G. Pavlov, Abel L. Peirson, Matteo Perri, Melissa Pesce-Rollins, Maura Pilia, Andrea Possenti, Simonetta Puccetti, Brian D. Ramsey, John Rankin, Ajay Ratheesh, Oliver J. Roberts, Roger W. Romani, Carmelo Sgro, Patrick Slane, Paolo Soffitta, Gloria Spandre, Douglas A. Swartz, Toru Tamagawa, Fabrizio Tavecchio, Roberto Taverna, Yuzuru Tawara, Allyn F. Tennant, Nicholas E. Thomas, Francesco Tombesi. 2023-04-03. A polarimetrically oriented X-ray stare at the accreting pulsar EXO 2030+375. https://doi.org/10.1051/0004-6361%2F202346581
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