Characterizing the Near-UV Environment of M Dwarfs

TL;DR

This study measures near-UV emission in 33 nearby M dwarfs using HST, providing crucial data to improve models of planetary habitability and stellar atmospheres, and aiding future space mission planning.

Contribution

It offers the first extensive near-UV observations of M dwarfs across a range of masses, informing models of stellar atmospheres and habitability zones.

Findings

Wide variation in UV emission between active and inactive stars.

Data constrains models of M dwarf atmospheres and habitability.

Supports understanding of magnetic activity and energy budgets.

Abstract

We report the results of our HST snapshot survey with the ACS HRC PR200L prism, designed to measure the near-UV emission in a sample of nearby M dwarfs. 33 stars were observed, spanning the mass range from 0.1 - 0.6 solar masses (T_eff ~ 2200K - 4000K) where the UV energy distributions vary widely between active and inactive stars. These observations provide much-needed constraints on models of the habitability zone and the atmospheres of possible terrestrial planets orbiting M dwarf hosts, and will be useful in refining the target selection for future space missions such as TPF. We compare our data with a new generation of M dwarf atmospheric models and discuss their implication for the chromospheric energy budget. These NUV data will also be valuable in conjunction with existing optical, FUV and X-ray data to explore unanswered questions regarding the dynamo generation and magnetic heating in low-mass stars.