Living with a Red Dwarf: FUV & X-ray emissions of dM stars and effects on hosted Planets

Abstract

Red Dwarf (dM) stars are overwhelmingly the most numerous stars in our Galaxy. These cool, faint and low mass stars make up more than 80% of all stars. Also dM stars have extremely long life times (longer than 50-100 Gyr). Determining the number of red dwarfs with planets and assessing planetary habitability (a planet's potential to develop and sustain life) is critically important because such studies would indicate how common life is in the universe. Our program - "Living with a Red Dwarf" - addresses these questions by investigating the long-term nuclear evolution and the coronal and chromospheric properties of red dwarf stars with widely different ages (~50 Myr – 12 Gyr). One major focus of the program is to study the magnetic-dynamo generated coronal and chromospheric X-ray–FUV/UV emissions and flare properties of a sample of dM0–5 stars. Observations carried out by FUSE of a number of young to old dM stars provide important data for understanding transition region heating in these stars with deep convective zones as well as providing measures of FUV irradiances. Also studied are the effects of X-ray–FUV emissions on possible hosted planets and impacts of this radiation on their habitability. Using these data we are constructing irradiance tables (X-UV irradiances) that can be used to model the effects of XUV radiation on planetary atmospheres and possible life on planetary surfaces. The initial results of this program are discussed.