ROSAT Pointed Observations of the Alpha Persei Cluster

We extend the results of a previous ROSAT x-ray raster survey of the open cluster α Persei by the analysis of three 22-25 ksec ROSAT PSPC pointings in this relatively nearby (d∼170 pc) and young (age ∼50 Myr) open cluster. The present study reports on those catalogued stars in the cluster region which are found to be associated, or possibly associated, with an x-ray source. Out of a total of 222 sources, approximately 80 sources are identified with a catalogued star. We detect all previously known K dwarfs, and a majority of M dwarfs within the higher sensitivity, inner PSPC regions. The results from the deep pointings are consistent with those from the previous raster survey of this cluster in terms of the x-ray luminosities measured for sources in common, the detection frequencies among cluster members as a function of spectral type, and the distribution of Lx as a function of color. The x-ray detections and upper limits provided by the PSPC observations have been combined with the raster survey results to create a merged raster/PSPC dataset reflecting the x-ray properties of the a Per cluster. The V sin i activity relation among G/K members is reviewed using the combined dataset. The α Per members with υ sin i> 30 km/s all show saturated levels of coronal activity, with the saturation level decreasing slowly from log(LX/Lbol)∼-3 at 50 km/s to log(LX/Lbol)∼ 3.4 at 200 km/s. The stars with υ sin i <15 km/s, most with only υ sin i upper limits, show a wide range in coronal activity (-4.3<LX/L bol<-2.9) -2.9); we assume that coronal activity in α Per increases with increasing rotation rate for υ sin i<15 km/s, but the functional form of the relation cannot be determined from existing data. The x-ray luminosity distribution functions among F-M α Per stars have been recomputed using the merged raster/PSPC dataset and compared to the Pleiades. The findings of the raster survey are confirmed, with F and G α Per dwarfs clearly exhibiting higher average emission than their Pleiades counterparts, while α Per K dwarfs show only slightly higher activity. The revised α Per M dwarf XLDF is in closer agreement with the Pleiades M dwarf distribution. We discuss the apparent detection in x rays of the one evolving blue supergiant member of this cluster, α Per itself. In addition, the sensitive PSPC observations may have detected x-ray sources associated with very low mass candidate cluster members at spectral type ∼MS. We also provide a summary of the x-ray flare characteristics (peak ∼10³¹ ergs/s) for three a Per members.