News on the X-ray emission from hot subdwarf stars

TL;DR

Recent X-ray observations of hot subdwarf stars using XMM-Newton and Chandra have expanded our understanding of their wind properties and binary systems, revealing emission mechanisms and potential for discovering new systems.

Contribution

This paper reviews recent X-ray observational results of hot subdwarf stars, highlighting new insights into their wind properties and binary systems.

Findings

Detection of X-ray emission in several hot subdwarfs

Evidence of wind accretion in binary systems

Potential discovery of new binary systems

Abstract

In latest years, the high sensitivity of the instruments on-board the XMM-Newton and Chandra satellites allowed us to explore the properties of the X-ray emission from hot subdwarf stars. The small but growing sample of X-ray detected hot subdwarfs includes binary systems, in which the X-ray emission is due to wind accretion onto a compact companion (white dwarf or neutron star), as well as isolated sdO stars, in which X-rays are probably due to shock instabilities in the wind. X-ray observations of these low-mass stars provide information which can be useful for our understanding of the weak winds of this type of stars and can lead to the discovery of particularly interesting binary systems. Here we report the most recent results we have recently obtained in this research area.