ROSAT X-RAY OBSERVATIONS OF THE YOUNG CLUSTER IC-348

We have observed the young stellar cluster IC 348 in X-rays for the fi rst time. In very deep pointings with the ROSAT PSPC and HRI we have d etected a total of 116 X-ray sources. Most sources appear to be embedd ed (A(V) approximate to 5) in their parent molecular cloud. We use nea r-infrared (J, H, K) photometric data from the study of Lada & Lada (1 995) to derive individual extinctions in order to calculate the X-ray luminosities. We find 56 stars to be probable new cluster members, pre sumably weak line T Tauri stars, because of their X-ray properties. Si nce previously 49 H alpha emission line stars and 17 proper motion mem bers were known, this nearly doubles the number of known member stars in IC 348. The early type (B5 - F5) stars do not appear to be intrinsi c Xray emitters. The late type stars display similar X-ray properties as those in other star forming regions. The weak line T Tauri stars se em To be stronger X-ray emitters than the classical T Tauri stars, but this difference may be caused by a selection effect. The total integr ated X-ray luminosity in IC 348 is at least 1.6 x 10(32) erg/sec in th e ROSAT band (0.1 - 2.4 keV). The possible influence of the X-radiatio n on the ionization state of the cloud and on its further evolution is briefly discussed. We report the detection of several large X-ray fla res in IC 348 on timescales of typically a few hours. For some sources we also find variability on time scales of several years by comparing their count rates in the two pointed ROSAT observations and the ROSAT All Sky Survey. About 45% of the X-ray sources show considerable vari ability on long or short time scales.