X-ray binaries with neutron stars at different accretion stages

Abstract

Different accretion regimes onto magnetized NSs in HMXBs are considered: wind-fed supersonic (Bondi) regime at high accretion rates $\dot{M}\gtrsim 4\times 10^{16}$~[g s${}^{-1}$] , subsonic settling regime at lower $\dot{M}$ and supercritical disc accretion during Roche lobe overflow. In wind-fed stage, NSs in HMXBs reach equilibrium spin periods $P^{\ast }$ proportional to binary orbital period $P_b$. 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 $P^{\ast }$ -- $P_b$ (the Corbet diagram), $P^{\ast }$ -- $L_x$ and $P_b$ -- $L_x$ distributions with those for the observed HMXBs (including Be X-ray binaries) and pulsating ULXs suggests the importance of the reduction of $P^{\ast }$ 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.

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

References in corpus (7)

• An Ultraluminous X-ray Source Powered by An Accreting Neutron Star
• The Evolution of Compact Binary Star Systems
• Discovery of coherent pulsations from the Ultraluminous X-ray Source NGC 7793 P13
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Cited by in corpus (2)

• Advances in Understanding High-Mass X-ray Binaries with INTEGRAL and Future Directions
• Wind-accreting Symbiotic X-ray Binaries