Abstract
We study 127 active late-type stars, including the well-known flare stars, in the extreme ultraviolet (EUV) region of the electromagnetic spectrum, using the ROSAT Wide Field Camera (WFC) survey observations. Our analysis includes photometry for all the stars in the sample, timing analysis of the observed photon events, and a statistical analysis for possible small-scale, low-level variability. 49 stars in our sample were detected in one or both EUV wavebands. A total of 35 flares were seen, from 23 stars, not all of them well-known flare stars. In addition, about half ofthe detections exhibited low-level variability. Further analysis reveals that the observed low-level variability was not due to rotational or orbital modulation, but rather was related to small-scale activity on the stars, possibly in the form of small amplitude, flare-like events which were too faint to be recognized as individual flares at the sensitivity of the WFC. We call this low-level activity 'milliflaring'. We also give estimated upper-limit count rates for the non-detections.
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