TY - JOUR
T1 - The X-Ray Polarimetry View of the Accreting Pulsar Cen X-3
AU - IXPE Collaboration
AU - Tsygankov, Sergey S.
AU - Doroshenko, Victor
AU - Poutanen, Juri
AU - Heyl, Jeremy
AU - Mushtukov, Alexander A.
AU - Caiazzo, Ilaria
AU - Di Marco, Alessandro
AU - Forsblom, Sofia V.
AU - González-Caniulef, Denis
AU - Klawin, Moritz
AU - La Monaca, Fabio
AU - Malacaria, Christian
AU - Marshall, Herman L.
AU - Muleri, Fabio
AU - Ng, Mason
AU - Suleimanov, Valery F.
AU - Sunyaev, Rashid A.
AU - Turolla, Roberto
AU - Agudo, Iván
AU - Antonelli, Lucio A.
AU - Bachetti, Matteo
AU - Baldini, Luca
AU - Baumgartner, Wayne H.
AU - Bellazzini, Ronaldo
AU - Bianchi, Stefano
AU - Bongiorno, Stephen D.
AU - Bonino, Raffaella
AU - Brez, Alessandro
AU - Bucciantini, Niccolò
AU - Capitanio, Fiamma
AU - Castellano, Simone
AU - Cavazzuti, Elisabetta
AU - Ciprini, Stefano
AU - Costa, Enrico
AU - De Rosa, Alessandra
AU - Del Monte, Ettore
AU - Di Gesu, Laura
AU - Di Lalla, Niccolò
AU - Donnarumma, Immacolata
AU - Dovčiak, Michal
AU - Ehlert, Steven R.
AU - Enoto, Teruaki
AU - Evangelista, Yuri
AU - Fabiani, Sergio
AU - Ferrazzoli, Riccardo
AU - Garcia, Javier A.
AU - Gunji, Shuichi
AU - Hayashida, Kiyoshi
AU - Iwakiri, Wataru
AU - Pavlov, George G.
N1 - Publisher Copyright:
© 2022. The Author(s).
PY - 2022/12/1
Y1 - 2022/12/1
N2 - The first X-ray pulsar, Cen X-3, was discovered 50 yr ago. Radiation from such objects is expected to be highly polarized due to birefringence of plasma and vacuum associated with propagation of photons in the 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 in either pulse phase-averaged (with a 3σ upper limit of 12%) or phase-resolved (the 3σ upper limits are 20%–30%) data. In the bright state, the polarization degree of 5.8% ± 0.3% and polarization angle of 49°. 6 ± 1°. 5 with a significance of about 20σ were measured from the spectropolarimetric analysis of the phase-averaged data. The phase-resolved analysis showed a significant anticorrelation 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.
AB - The first X-ray pulsar, Cen X-3, was discovered 50 yr ago. Radiation from such objects is expected to be highly polarized due to birefringence of plasma and vacuum associated with propagation of photons in the 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 in either pulse phase-averaged (with a 3σ upper limit of 12%) or phase-resolved (the 3σ upper limits are 20%–30%) data. In the bright state, the polarization degree of 5.8% ± 0.3% and polarization angle of 49°. 6 ± 1°. 5 with a significance of about 20σ were measured from the spectropolarimetric analysis of the phase-averaged data. The phase-resolved analysis showed a significant anticorrelation 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.
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U2 - 10.3847/2041-8213/aca486
DO - 10.3847/2041-8213/aca486
M3 - Article
AN - SCOPUS:85144807046
SN - 2041-8205
VL - 941
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
M1 - L14
ER -