X-ray polarimetry of X-ray pulsar X Persei: another orthogonal rotator?
Abstract
X Persei is a persistent low-luminosity X-ray pulsar of period of 835 s in a Be binary system. The field strength at the neutron star surface is not known precisely, but indirect signs indicate a magnetic field above G, which makes the object one of the most magnetized known X-ray pulsars. Here we present the results of observations X Persei performed with the Imaging X-ray Polarimetry Explorer (IXPE). The X-ray polarization signal was found to be strongly dependent on the spin phase of the pulsar. The energy-averaged polarization degree in 3-8 keV band varied from several to 20 per cent over the pulse with a positive correlation with the pulsed X-ray flux. The polarization angle shows significant variation and makes two complete revolutions during the pulse period resulting in nearly nil pulse-phase averaged polarization. Applying the rotating vector model to the IXPE data we obtain the estimates for the rotation axis inclination and its position angle on the sky as well as for the magnetic obliquity. The derived inclination is close to the orbital inclination reported earlier for X Persei. The polarimetric data imply a large angle between the rotation and magnetic dipole axes, which is similar to the result reported recently for the X-ray pulsar GRO J100857. After eliminating the effect of polarization angle rotation over the pulsar phase using the best-fitting rotating vector model, the strong dependence of the polarization degree with energy was discovered with its value increasing from 0% at 2 keV to 30% at 8 keV.
Cite
@article{arxiv.2303.17325,
title = {X-ray polarimetry of X-ray pulsar X Persei: another orthogonal rotator?},
author = {A. A. Mushtukov and S. S. Tsygankov and J. Poutanen and V. Doroshenko and A. Salganik and E. Costa and A. Di Marco and J. Heyl and F. La Monaca and A. A. Lutovinov and I. A. Mereminsky and A. Papitto and A. N. Semena and A. E. Shtykovsky and V. F. Suleimanov and S. V. Forsblom and D. González-Caniulef and C. Malacaria and R. A. Sunyaev and I. Agudo and L. A. Antonelli and M. Bachetti and L. Baldini and W. H. Baumgartner and R. Bellazzini and S. Bianchi and S. D. Bongiorno and R. Bonino and A. Brez and N. Bucciantini and F. Capitanio and S. Castellano and E. Cavazzuti and C. -T. Chen and S. Ciprini and A. De Rosa and E. Del Monte and L. Di Gesu and N. Di Lalla and I. Donnarumma and M. Dovčiak and S. R. Ehlert and T. Enoto and Y. Evangelista and S. Fabiani and R. Ferrazzoli and J. A. Garcia and S. Gunji and K. Hayashida and W. Iwakiri and S. G. Jorstad and P. Kaaret and V. Karas and F. Kislat and T. Kitaguchi and J. J. Kolodziejczak and H. Krawczynski and L. Latronico and I. Liodakis and S. Maldera and A. Manfreda and F. Marin and A. P. Marscher and H. L. Marshall and F. Massaro and G. Matt and I. Mitsuishi and T. Mizuno and F. Muleri and M. Negro and C. -Y. Ng and S. L. O'Dell and N. Omodei and C. Oppedisano and G. G. Pavlov and A. L. Peirson and M. Perri and M. Pesce-Rollins and P. -O. Petrucci and M. Pilia and A. Possenti and S. Puccetti and B. D. Ramsey and J. Rankin and A. Ratheesh and O. J. Roberts and R. W. Romani and C. Sgrò and P. Slane and P. Soffitta and G. Spandre and D. A. Swartz and T. Tamagawa and F. Tavecchio and R. Taverna and Y. Tawara and A. F. Tennant and N. E. Thomas and F. Tombesi and A. Trois and R. Turolla and J. Vink and M. C. Weisskopf and K. Wu and F. Xie and S. Zane},
journal= {arXiv preprint arXiv:2303.17325},
year = {2023}
}
Comments
11 pages, 7 figures, submitted to MNRAS