Neutron star masses from hydrodynamical effects in obscured supergiant high mass X-ray binaries

Abstract

Context. A population of obscured supergiant high mass X-ray binaries has been discovered by INTEGRAL. X-ray wind tomography of IGR J17252-3616 inferred a slow wind velocity to account for the enhanced obscuration.
Aims: The main goal of this study is to understand under which conditions high obscuration could occur.
Methods: We have used an hydrodynamical code to simulate the flow of the stellar wind around the neutron star. A grid of simulations was used to study the dependency of the absorbing column density and of the X-ray light-curves on the model parameters. A comparison between the simulation results and the observations of IGR J17252-3616 provides an estimate on these parameters.
Results: We have constrained the wind terminal velocity to 500-600 km s^-1 and the neutron star mass to 1.75-2.15 M_⊙.
Conclusions: We have confirmed that the initial hypothesis of a slow wind velocity with a moderate mass loss rate is valid. The mass of the neutron star can be constrained by studying its impact on the accretion flow.