X-ray pulsar GRO J1008-57 as an orthogonal rotator

0574443 - ASÚ 2024 RIV FR eng J - Journal Article
Tsygankov, S. S. - Doroshenko, V. - Mushtukov, A. A. - Svoboda, Jiří - Dovčiak, Michal - Karas, Vladimír … Total 102 authors
X-ray pulsar GRO J1008-57 as an orthogonal rotator.
Astronomy & Astrophysics. Roč. 675, July (2023), č. článku A48. ISSN 0004-6361. E-ISSN 1432-0746
R&D Projects: GA ČR(CZ) GX21-06825X
Institutional support: RVO:67985815
Keywords : accretion disks * magnetic fields * pulsars
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 6.5, year: 2022
Method of publishing: Open access

X-ray polarimetry is a unique way to probe the geometrical configuration of highly magnetized accreting neutron stars (X-ray pulsars). GRO J1008-57 is the first transient X-ray pulsar observed at two different flux levels by the Imaging X-ray Polarimetry Explorer (IXPE) during its outburst in November 2022. We find the polarization properties of GRO J1008-57 to be independent of its luminosity, with the polarization degree varying between nondetection and about 15% over the pulse phase. Fitting the phase-resolved spectro-polarimetric data with the rotating vector model allowed us to estimate the pulsar inclination (130 & DEG, which is in good agreement with the orbital inclination), the position angle (75 & DEG) of the pulsar spin axis, and the magnetic obliquity (& SIM,74 & DEG,). This makes GRO J1008-57 the first confidently identified nearly orthogonal rotator among X-ray pulsars. We discuss our results in the context of the neutron star atmosphere models and theories of the axis alignment of accreting pulsars.
Permanent Link: https://hdl.handle.net/11104/0345568