Neutron star masses from hydrodynamical effects in obscured sgHMXBs

TL;DR

This study uses hydrodynamical simulations to analyze the wind flow around neutron stars in obscured sgHMXBs, constraining wind velocities and neutron star masses based on observational data.

Contribution

It introduces a hydrodynamical modeling approach to estimate neutron star masses and wind properties in obscured sgHMXBs, validating the slow wind hypothesis.

Findings

Wind terminal velocity constrained to 500-600 km/s

Neutron star mass estimated between 1.75 and 2.15 solar masses

Confirmed the slow wind velocity hypothesis

Abstract

A population of obscured supergiant High Mass X-ray Binaries (sgHMXBs) has been discovered by INTEGRAL. X-ray wind tomography of IGR J17252-3616 inferred a slow wind velocity to account for the enhanced obscuration. The main goal of this study is to understand under which conditions high obscuration could occur. 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. We have constrained the wind terminal velocity to 500-600 km/s and the neutron star mass to 1.75-2.15 solar masses. 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.