X-ray Variability of dM Stars Observed by EXOSAT

We have studied the quiescent X-ray emission from 6 dM stars observed by EXOSAT, searching for variability on time scales in the range 50 – 6000 sec. Excluding from the analysis obvious large flares we analysed the apparently “quiescent” emission using an optimized χ 2 test which allows a determination of the variability amplitude and time scale or upper limits thereof.