# Properties of the Interstellar Medium along Sight Lines to Nearby Planet Hosting Stars

## TL;DR

This study uses high-resolution UV spectra of nearby exoplanet host stars to analyze interstellar medium properties along their sight lines and to investigate the presence of astrospheric absorption, revealing the stars are in ionized interstellar regions.

## Contribution

It provides detailed interstellar medium measurements along sight lines to exoplanet hosts and links these to local cloud velocities, enhancing understanding of star-planet environments.

## Key findings

- Identified three interstellar velocity components per star.
- None of the stars show astrospheric absorption, indicating ionized surroundings.
- Compiled interstellar properties for exoplanets within 20 pc of the Sun.

## Abstract

We analyze high-resolution ultraviolet spectra of three nearby exoplanet host stars (HD 192310, HD 9826, and HD 206860) to study interstellar properties along their lines of sight and to search for the presence of astrospheric absorption. Using HST/STIS spectra of the Lyman-alpha, Mg II, and Fe II lines, we identify three interstellar velocity components in the lines of sight to each star. We can reliably assign eight of the nine components to partially ionized clouds found by Redfield & Linsky (2008) on the basis of the star's location in Galactic coordinates and agreement of measured radial velocities with velocities predicted from the cloud velocity vectors. None of the stars show blue-shifted absorption indicative of an astrosphere, implying that the stars are in regions of ionized interstellar gas. Coupling astrospheric and local interstellar medium measurements is necessary to evaluate the host star electromagnetic and particle flux, which have profound impacts on the atmospheres of their orbiting planets. We present a table of all known exoplanets located within 20 pc of the Sun listing their interstellar properties and velocities predicted from the local cloud velocity vectors.