The X-ray polarimetry view of the accreting pulsar Cen X-3
Creators: name: Tsygankov, Sergey S.
name: Doroshenko, Victor
name: Poutanen, Juri
name: Heyl, Jeremy
name: Mushtukov, Alexander A.
name: Caiazzo, Ilaria
name: Di Marco, Alessandro
name: Forsblom, Sofia V.
name: González-Caniulef, Denis
name: Klawin, Moritz
name: La Monaca, Fabio
name: Malacaria, Christian
name: Marshall, Herman L.
name: Muleri, Fabio
name: Ng, Mason
name: Suleimanov, Valery F.
name: Sunyaev, Rashid A.
name: Turolla, Roberto
name: Agudo, Iván
name: Antonelli, Lucio A.
name: Bachetti, Matteo
name: Baldini, Luca
name: Baumgartner, Wayne H.
name: Bellazzini, Ronaldo
name: Bianchi, Stefano
name: Bongiorno, Stephen D.
name: Bonino, Raffaella
name: Brez, Alessandro
name: Bucciantini, Niccolò
name: Capitanio, Fiamma
name: Castellano, Simone
name: Cavazzuti, Elisabetta
name: Ciprini, Stefano
name: Costa, Enrico
name: De Rosa, Alessandra
name: Del Monte, Ettore
name: Di Gesu, Laura
name: Di Lalla, Niccolò
name: Donnarumma, Immacolata
name: Dovčiak, Michal
name: Ehlert, Steven R.
name: Enoto, Teruaki
name: Evangelista, Yuri
name: Fabiani, Sergio
name: Ferrazzoli, Riccardo
name: Garcia, Javier A.
name: Gunji, Shuichi
name: Hayashida, Kiyoshi
name: Iwakiri, Wataru
name: Jorstad, Svetlana G.
name: Karas, Vladimir
name: Kitaguchi, Takao
name: Kolodziejczak, Jeffery J.
name: Krawczynski, Henric
name: Latronico, Luca
name: Liodakis, Ioannis
name: Maldera, Simone
name: Manfreda, Alberto
name: Marin, Frédéric
name: Marinucci, Andrea
name: Marscher, Alan P.
name: Matt, Giorgio
name: Mitsuishi, Ikuyuki
name: Mizuno, Tsunefumi
name: Ng, C. -Y.
name: O'Dell, Stephen L.
name: Omodei, Nicola
name: Oppedisano, Chiara
name: Papitto, Alessandro
name: Pavlov, George G.
name: Peirson, Abel L.
name: Perri, Matteo
name: Pesce-Rollins, Melissa
name: Petrucci, Pierre-Olivier
name: Pilia, Maura
name: Possenti, Andrea
name: Puccetti, Simonetta
name: Ramsey, Brian D.
name: Rankin, John
name: Ratheesh, Ajay
name: Romani, Roger W.
name: Sgrò, Carmelo
name: Slane, Patrick
name: Soffitta, Paolo
name: Spandre, Gloria
name: Tamagawa, Toru
name: Tavecchio, Fabrizio
name: Taverna, Roberto
name: Tawara, Yuzuru
name: Tennant, Allyn F.
name: Thomas, Nicolas E.
name: Tombesi, Francesco
name: Trois, Alessio
name: Vink, Jacco
name: Weisskopf, Martin C.
name: Wu, Kinwah
name: Xie, Fei
name: Zane, Silvia
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Cen X-3 is the first X-ray pulsar discovered 50 years ago. Radiation from such objects is expected to be highly polarized due to birefringence of plasma and vacuum associated with propagation of photons in presence of the strong magnetic field. Here we present results of the observations of Cen X-3 performed with the Imaging X-ray Polarimetry Explorer. The source exhibited significant flux variability and was observed in two states different by a factor of ~20 in flux. In the low-luminosity state no significant polarization was found either in pulse phase-averaged (with the 3$σ$ upper limit of 12%) or phase-resolved data (the 3$σ$ upper limits are 20-30%). In the bright state the polarization degree of 5.8$\pm$0.3% and polarization angle of $49.6°\pm1.5°$ with significance of about 20$σ$ was measured from the spectro-polarimetric analysis of the phase-averaged data. The phase-resolved analysis showed a significant anti-correlation between the flux and the polarization degree as well as strong variations of the polarization angle. The fit with the rotating vector model indicates a position angle of the pulsar spin axis of about 49$°$ and a magnetic obliquity of 17$°$. The detected relatively low polarization can be explained if the upper layers of the neutron star surface are overheated by the accreted matter and the conversion of the polarization modes occurs within the transition region between the upper hot layer and a cooler underlying atmosphere. A fraction of polarization signal can also be produced by reflection of radiation from the neutron star surface and the accretion curtain.
description: Submitted to ApJL. 18 pages, 12 figures