English

X-ray binaries with neutron stars at different accretion stages

High Energy Astrophysical Phenomena 2020-01-20 v1

Abstract

Different accretion regimes onto magnetized NSs in HMXBs are considered: wind-fed supersonic (Bondi) regime at high accretion rates M˙4×1016\dot M\gtrsim 4\times 10^{16}~[g s1^{-1}] , subsonic settling regime at lower M˙\dot M and supercritical disc accretion during Roche lobe overflow. In wind-fed stage, NSs in HMXBs reach equilibrium spin periods PP^* proportional to binary orbital period PbP_b. At supercritical accretion stage, the system may appear as a pulsating ULX. Population synthesis of Galactic HMXBs using standard assumptions on the binary evolution and NS formation is presented. Comparison of the model PP^* -- PbP_b (the Corbet diagram), PP^* -- LxL_x and PbP_b -- LxL_x distributions with those for the observed HMXBs (including Be X-ray binaries) and pulsating ULXs suggests the importance of the reduction of PP^* in non-circular orbits, explaining the location of Be X-ray binaries in the model Corbet diagram, and the universal parameters of pulsating ULXs depending only on the NS magnetic fields.

Keywords

Cite

@article{arxiv.1811.02842,
  title  = {X-ray binaries with neutron stars at different accretion stages},
  author = {Konstantin Postnov and Aleksandre Kuranov and Lev Yungelson},
  journal= {arXiv preprint arXiv:1811.02842},
  year   = {2020}
}

Comments

9 pages, 10 figures, to appear in Proc. IAUS 346