# Wind-accreting Symbiotic X-ray Binaries

## TL;DR

This paper introduces an improved model for symbiotic X-ray binaries that accounts for non-stationary accretion processes, better matching observed distributions of system properties and suggesting low matter expulsion efficiency during binary evolution.

## Contribution

The model incorporates non-stationary quasi-spherical accretion and stricter criteria for plasma entry and settling, enhancing agreement with observed system distributions.

## Key findings

- Model reproduces observed distributions of orbital and spin periods.
- Galactic number of systems aligns with observations.
- Low matter expulsion efficiency is necessary for system formation.

## Abstract

We present a new model of the population of symbiotic X-ray binaries (SyXBs) that takes into account non-stationary character of quasi-spherical sub-sonic accretion of the red giant's stellar wind onto slowly rotating neutron stars. Updates of the earlier models are given, which include more strict criteria of slow NS rotation for plasma entry into the NS magnetosphere via Rayleigh-Taylor instability, as well as more strict conditions for settling accretion for slow stellar winds, with an account of variations in the specific angular momentum of captured stellar wind in eccentric binaries. These modifications enabled a more adequate description of the distributions of observed systems over binary orbital periods, NS spin periods and their X-ray luminosity in the $\sim 10^{32}-10^{36}$~erg s$^{-1}$ range and brought their model Galactic number into reasonable agreement with the observed one. Reconciliation of the model and observed orbital periods of SyXBs requires a low efficiency of matter expulsion from common envelopes during the evolution that results in the formation of NS-components of symbiotic X-ray systems.