Author:
Malacaria Christian,Heyl Jeremy,Doroshenko Victor,Tsygankov Sergey S.,Poutanen Juri,Forsblom Sofia V.,Capitanio Fiamma,Di Marco Alessandro,Du Yujia,Ducci Lorenzo,La Monaca Fabio,Lutovinov Alexander A.,Marshall Herman L.,Mereminskiy Ilya A.,Molkov Sergey V.,Mushtukov Alexander A.,Ng Mason,Petrucci Pierre-Olivier,Santangelo Andrea,Shtykovsky Andrey E.,Suleimanov Valery F.,Agudo Iván,Antonelli Lucio A.,Bachetti Matteo,Baldini Luca,Baumgartner Wayne H.,Bellazzini Ronaldo,Bianchi Stefano,Bongiorno Stephen D.,Bonino Raffaella,Brez Alessandro,Bucciantini Niccolò,Castellano Simone,Cavazzuti Elisabetta,Chen Chien-Ting,Ciprini Stefano,Costa Enrico,De Rosa Alessandra,Del Monte Ettore,Di Gesu Laura,Di Lalla Niccolò,Donnarumma Immacolata,Dovčiak Michal,Ehlert Steven R.,Enoto Teruaki,Evangelista Yuri,Fabiani Sergio,Ferrazzoli Riccardo,Garcia Javier A.,Gunji Shuichi,Hayashida Kiyoshi,Iwakiri Wataru,Jorstad Svetlana G.,Kaaret Philip,Karas Vladimir,Kislat Fabian,Kitaguchi Takao,Kolodziejczak Jeffery J.,Krawczynski Henric,Latronico Luca,Liodakis Ioannis,Maldera Simone,Manfreda Alberto,Marin Frédéric,Marinucci Andrea,Marscher Alan P.,Massaro Francesco,Matt Giorgio,Mitsuishi Ikuyuki,Mizuno Tsunefumi,Muleri Fabio,Negro Michela,Ng Chi-Yung,O’Dell Stephen L.,Omodei Nicola,Oppedisano Chiara,Papitto Alessandro,Pavlov George G.,Peirson Abel L.,Perri Matteo,Pesce-Rollins Melissa,Pilia Maura,Possenti Andrea,Puccetti Simonetta,Ramsey Brian D.,Rankin John,Ratheesh Ajay,Roberts Oliver J.,Romani Roger W.,Sgrò Carmelo,Slane Patrick,Soffitta Paolo,Spandre Gloria,Swartz Douglas A.,Tamagawa Toru,Tavecchio Fabrizio,Taverna Roberto,Tawara Yuzuru,Tennant Allyn F.,Thomas Nicholas E.,Tombesi Francesco,Trois Alessio,Turolla Roberto,Vink Jacco,Weisskopf Martin C.,Wu Kinwah,Xie Fei,Zane Silvia
Abstract
Accreting X-ray pulsars (XRPs) are presumed to be 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, namely, 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, an analysis of the EXO 2030+375 data returns a low polarization degree of 0%–3% in the phase-averaged study and a variation in the range of 2%–7% in the phase-resolved study. Using the rotating vector model, we constrained the geometry of the system and obtained a value of ∼60° for the magnetic obliquity. When considering the estimated pulsar inclination of ∼130°, this also indicates that the magnetic axis swings close to the observer’s line of sight. Our joint polarimetric, spectral, and timing analyses hint toward a complex accreting geometry, whereby magnetic multipoles with an asymmetric topology and gravitational light bending significantly affect the behavior of the observed source.
Subject
Space and Planetary Science,Astronomy and Astrophysics