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As part of Villanova's Living with a Red Dwarf program, we have obtained UV,X-ray and optical data of the Population II red dwarf -- Kapteyn's Star.Kapteyn's Star is noteworthy for its large proper motions and high RV of ~+245km s^-1. As the nearest Pop II red dwarf, it serves as an old age anchor forcalibrating Activity/Irradiance-Rotation-Age relations, and an important testbed for stellar dynamos and the resulting X-ray -- UV emissions of slowlyrotating, near-fully convective red dwarf stars. Adding to the notoriety,Kapteyn's Star has recently been reported to host two super-Earth candidates,one of which (Kapteyn b) is orbiting within the habitable zone (Anglada-Escudeet al. 2014a, 2015). However, Robertson et al. (2015) questioned the planet'sexistence since its orbital period may be an artifact of activity, related tothe star's rotation period. Because of its large Doppler-shift, measures of theimportant, chromospheric H I Lyman-alpha 1215.67A emission line can be reliablymade, because it is mostly displaced from ISM and geo-coronal sources.Lyman-alpha emission dominates the FUV region of cool stars. Our measures canhelp determine the X-ray--UV effects on planets hosted by Kapteyn's Star, andplanets hosted by other old red dwarfs. Stellar X-ray and Lyman-alpha emissionshave strong influences on the heating and ionization of upper planetaryatmospheres and can (with stellar winds and flares) erode or even eliminateplanetary atmospheres. Using our program stars, we have reconstructed the pastexposures of Kapteyn's Star's planets to coronal -- chromospheric XUV emissionsover time.

Living with a Red Dwarf: Rotation and X-ray and Ultraviolet Properties of the Halo Population Kapteyn's Star