ROSAT POINTED OBSERVATIONS OF THE ALPHA-PERSEI CLUSTER

We extend the results of a previous ROSAT x-ray raster survey of the o pen cluster alpha Persli by the analysis of three 22-25 ksec ROSATPSPC pointings in this relatively nearby (d similar to 170 pc) and young ( age similar to 50 Myr) open cluster. The present study reports on thos e catalogued stars in the cluster region which are found to be associa ted, or possibly associated, with an x-ray sourer, Out of a total of 2 22 sources, approximately 80 sources are identified with a catalogued star, We detect all previously known K dwarfs, and a majority of M dwa rfs within the higher sensitivity, inner PSPC regions. The results fro m the deep pointings are consistent with those from the previous raste r survey of this cluster in terms of the x-ray luminosities measured f or sources in common, the detection frequencies among cluster members as a function of spectral type, and the distribution of L(X) as a func tion of color. The x-ray detections and upper limits provided by tile PSPC observations have been combined with the raster survey results to create a merged raster/PSPC dataset reflecting the x-ray properties o f the alpha Per cluster. The upsilon sin i-activity relation among G/K members is reviewed using the combined dataset. The alpha Per members with upsilon sin i > 30 km/s all show saturated levels of coronal act ivity, with tile saturation level decreasing slowly from log(L(X)/L(bo l))similar to-3 at 50 km/s to log(L(X)/L(bol)similar to-3.4 at 200 km/ s. The stars with upsilon sin i < 15 km/s, most with only upsilon sin i upper limits, show a wide range in coronal activity (-4.3 < L(X)/L(b ol) < -2.9), we assume that coronal activity in alpha Per increases wi th increasing rotation rate for v sin i < 15 km/s, but the functional form of the relation cannot be determined from existing data. The x-ra y luminosity distribution functions among F-M alpha Per stars have bee n recomputed using the merged raster/PSPC dataset and compared to the Pleiades, The findings of the raster survey are confirmed, with F and G alpha Per dwarfs clearly exhibiting higher average emission than the ir Pleiades counterparts, while alpha Per K dwarfs show only slightly higher activity. The revised alpha Per M dwarf XLDF is in closer agree ment with the Pleiades M dwarf distribution. We discuss the apparent d etection in x rays of the one evolving blue supergiant member or this cluster, a Per itself. In addition, the sensitive PSPC observations ma y have detected x-ray sources associated with very low mass candidate cluster members al spectral type similar to M5, We also provide a summ ary of the x-ray flare characteristics (peak similar to 10(31) ergs/s) for three alpha Per members. (C) 1996 American Astronomical Society.