Name/Affiliation: Scott G. Engle (Villanova University)
Current Results of the Living with a Red Dwarf Program: Activity-Rotation-Age Relationships for M-dwarfs
Red Dwarfs (dM-stars) make up over 75% of the local stellar population. This is among the reasons they are being targeted in more planet-hunting programs. As such, the ability to accurately estimate the age of a field dM star is of critical importance. However, due to their long lifetimes and very slow nuclear evolution, the best method for determining ages is likely through “magnetic tracers” such as X-UV activity levels and stellar rotation rates. The Living with a Red Dwarf program’s database of dM-stars with photometrically determined rotation periods (via starspot modulations) is becoming substantial. It has recently been expanded to include dM stars with well-detached WD companions – through which reliable ages can be determined. When combined with dM stars possessing cluster/population memberships, or specific kinematics, a full range of “calibrators” is being realized. We report on our continuing efforts to build reliable Activity-Rotation-Age relationships for dM-stars, utilizing X-UV measures obtained by us with HST and Chandra, as well as archival data. Such relationships permit the assessment of the habitability of planets hosted by red dwarfs, by delineating the X-UV radiation environments these planets are exposed to, and have been exposed to in the past. After proper calibration, the relationships can also permit the age of a field red dwarf (and their hosted planets) to be determined through measures of either its rotation period or X-UV activity level. We gratefully acknowledge the support from NSF/RUI Grant AST 1009903, Chandra Grant GO-13200633, HST Grants GO-12124X and GO-13020X.