IXPE Observations of the Quintessential Wind-accreting X-Ray Pulsar Vela X-1

0572125 - ASÚ 2024 RIV US eng J - Journal Article
Forsblom, S. - Poutanen, J. - Tsygankov, S. S. - Dovčiak, Michal - Karas, Vladimír … Total 101 authors
IXPE Observations of the Quintessential Wind-accreting X-Ray Pulsar Vela X-1.
Astrophysical Journal Letters. Roč. 947, č. 2 (2023), č. článku L20. ISSN 2041-8205. E-ISSN 2041-8213
Institutional support: RVO:67985815
Keywords : pulsars * starlight polarization * neutron stars
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 7.9, year: 2022
Method of publishing: Open access

The radiation from accreting X-ray pulsars was expected to be highly polarized, with some estimates for the polarization degree of up to 80%. However, phase-resolved and energy-resolved polarimetry of X-ray pulsars is required in order to test different models and to shed light on the emission processes and the geometry of the emission region. Here we present the first results of the observations of the accreting X-ray pulsar Vela X-1 performed with the Imaging X-ray Polarimetry Explorer. Vela X-1 is considered to be the archetypal example of a wind-accreting, high-mass X-ray binary system, consisting of a highly magnetized neutron star accreting matter from its supergiant stellar companion. The spectropolarimetric analysis of the phase-averaged data for Vela X-1 reveals a polarization degree (PD) of 2.3% +/- 0.4% at the polarization angle (PA) of47.degrees 3 +/- 5.degrees 4. A low PD is consistent with the results obtained for other X-ray pulsars and is likely related to the inverse temperature structure of the neutron star atmosphere. The energy-resolved analysis shows the PD above 5 keV reaching 6%-10% and a similar to 90 degrees difference in the PA compared to the data in the 2-3 keV range. The phase-resolved spectropolarimetric analysis finds a PD in the range 0%-9% with the PA varying between80 degrees and 40 degrees.
Permanent Link: https://hdl.handle.net/11104/0342978