X-ray detection of astrospheres around three main-sequence stars and their mass-loss rates

TL;DR

This study detects X-ray emission from astrospheres of three main-sequence stars to estimate their stellar wind mass-loss rates, providing a new observational method to measure stellar winds that are otherwise difficult to constrain.

Contribution

The paper presents the first detection of charge-exchange X-ray emission from stellar astrospheres, enabling direct estimation of stellar mass-loss rates for multiple stars.

Findings

Detected X-ray emission from three stellar astrospheres.

Estimated mass-loss rates are significantly higher than the solar rate.

Compared results with the hydrogen wall method and established upper limits.

Abstract

Stellar winds of cool main sequence stars are very difficult to constrain observationally. One way to measure stellar mass loss rates is to detect soft X-ray emission from stellar astrospheres produced by charge exchange between heavy ions of the stellar wind and cold neutrals of the interstellar medium (ISM) surrounding the stars. Here we report detections of charge-exchange induced X-ray emission from the extended astrospheres of three main sequence stars, 70 Ophiuchi, epsilon Eridani, and 61 Cygni based on analysis of observations by XMM-Newton. We estimate the corresponding mass loss rates to be 66.5 +- 11.1, 15.6 +- 4.4, and 9.6 +- 4.1 times the solar mass loss rate for 70 Ophiuchi, epsilon Eridani, and 61 Cygni, respectively, and compare our results to the hydrogen wall method. We also place upper limits on the mass loss rates of several other main sequence stars. This method has potential utility for determining the mass loss rates from X-ray observations showing spatial extension beyond a coronal point source.