CORRELATIONS OF CORONAL X-RAY-EMISSION WITH ACTIVITY, MASS, AND AGE OF THE NEARBY K-DWARFS AND M-DWARFS

Using the ROSAT telescope, we have detected X-ray emission from 87% of all known K and M dwarfs within 7 pc of the Sun. Analysis of this vol ume-limited sample of K and M dwarfs reveals no evidence for a decreas e in coronal heating efficiency (as measured by L(X)/L(bol)) among the lowest mass, presumably fully convective, late-M dwarfs. Furthermore, our results indicate that those stars which exhibit little chromosphe ric activity (i.e., dM and dK stars) do indeed have cooler and weaker coronae than the more active dMe stars. While we also see a correlatio n between coronal temperature/strength and metallicity (and presumably age), no such correlation is seen with kinematic class. The latter re sult leads us to suggest that kinematic class is a poor age indicator for the nearby stars.