We present a final summary of all ROSAT X-ray observations of nearby stars .
All available ROSAT observations with the ROSAT PSPC , HRI and WFC have been matched with the CNS4 catalog of nearby stars and the results gathered in the Ne arby X -ray and XU V-emitting S tars data base , available via www from the Home Page of the Hamburger Sternwarte at the URL http : //www.hs.uni-hamburg.de/DE/For/Gal/Xgroup/nexxus .
New volume-limited samples of F/G-stars ( d _ { lim } = 14 pc ) , K-stars ( d _ { lim } = 12 pc ) , and M-stars ( d _ { lim } = 6 pc ) are constructed within which detection rates of more than 90 % are obtained ; only one star ( GJ 1002 ) remains undetected in a pointed follow-up observation .
F/G-stars , K-stars and M-stars have indistinguishable surface X-ray flux distributions , and the lower envelope of the observed distribution at F _ { X } \approx 10 ^ { 4 } erg/cm ^ { 2 } /sec is the X-ray flux level observed in solar coronal holes .
Large amplitude variations in X-ray flux are uncommon for solar-like stars , but maybe more common for stars near the bottom of the main sequence ; a large amplitude flare is reported for the M star LHS 288 .
Long term X-ray light curves are presented for \alpha Cen A/B and Gl 86 , showing variations on time scales of weeks and demonstrating that \alpha Cen B is a flare star .