ROSAT OBSERVATIONS OF STELLAR FLARES

X-ray observations of stellar flares obtained during the ROSA T all-sky survey as well as in the ROSA T pointing program are discussed. The ROSAT all-sky survey allowed-for the first time-an unbiased search for stellar flares among all types of stars. A fundamentally new result obtained is that nares can occur on all types of late-type stars, thus supporting the view that the X-ray emission from these stars is controlled by magnetic processes. Long-duration flares can be studied with the all-sky survey data particularly well, and an especially well-observed long-duration flare event on the flare star EV Lacertae is presented and discussed in detail. Finally, the issue of time variability on the shortest detectable timescales and the question of microflaring is discussed using ROSA T data from a pointed observation of UV Ceti.