Topic: Cool Stars as Exoplanet Hosts
We present an X-ray characterization of the CARMENES sample of M-dwarfs. CARMENES will monitor the radial velocities of about 300 M-dwarfs for five years in a search for Earth-like planets in their habitable zones. On such stars magnetic activity is ubiquitously presednt and its various manifestations turn out to be an important obstacle to detect low mass, long-period planets. Hence it is essential to characterize the sampled low mass stars in their activity properties to disentangle RV variations due to spots and other stellar activity from those caused by the presence of planetary companions. The primary database for our X-ray analysis is provided by the ROSAT all-sky survey (RASS) which has produced complete and unbiased samples of X-ray sources; we also consider X-ray data from the XMM-Newton and Chandra Observatories as well as the future eROSITA X-ray all-sky survey.