086111

Recently a large number of rotation period measurements of low mass stars of type M have become available. Surprisingly comma one finds that in addition to the well-known rapid rotators a population of very slowly rotating M dwarfs with rotation periods exceeding 100 days. These slow rotators pose a challenge for the usual rotation- activity paradigm comma since about a third of these stars have been detected in the ROSAT all-sky survey comma even though the RASS data did not probe significantly deeper than the saturation limit for stars of masses below 0.6 MSun. We thus propose XMM follow-up for a complete sample of nearby comma undetected low mass stars with long rotation periods down to a sensitivity limit of L_X-L_bol virgul 2 10**-5 to study the relation between X-ray activity and rotation in these stars.