Living with a Red Dwarf: Constraining the Ages of dM Stars From Rotation-Activity-Age Relations

We report on the progress of the "Living with a Red Dwarf” Program, a multi-frequency study of red dwarfs (dM stars) with ages from 10 Myr to 13 Gyr. dM stars are the most numerous stars in our Galaxy, comprising >75% of all known stars. Recently, planets (including large terrestrial planets) have been discovered orbiting several nearby dM stars. Our program aims to understand the magnetic activity, coronal physics, and XUV spectral irradiances of dM stars of different ages, and what the effects would be on orbiting planets. As a part of this program, we are developing relationships among age, rotation and markers of magnetic activity (XUV emissions). Using our own photometry combined with that of the ASAS3 program, we have determined the rotation periods and possible activity cycles of an increasing number of dM stars. We are using ROSAT, ASCA, XMM and Chandra X-ray observations and are combining these with EUV, and FUV-UV data (from EUVE, FUSE and IUE or HST) to form XUV spectral irradiance tables of dM stars covering a wide range of ages and XUV fluxes. From the relationships derived to date, we have been able to provide age estimates for field dM0-5 stars based on their X-ray luminosities. Of particular importance has been the determinations of ages for dM stars currently known to host planets.

We gratefully acknowledge suport by grants from NSF/RUI AST-507536 and NASA grants NNX06AD386 and NNG04G038G.