ROSAT X-ray observations of the young cluster IC348

Thomas Preibisch, Hans Zinnecker, & George H. Herbig

Astronomy & Astrophysics 310, 456-473, (1996)


We have observed the young stellar cluster IC348 in X-rays for the first time. In very deep pointings with the ROSAT PSPC and HRI we have detected a total of 116 X-ray sources. Most sources appear to be embedded (A_V approx 5) in their parent molecular cloud. We use near-infrared (J,H,K) photometric data from the study of Lada \& Lada (1995) to derive individual extinctions in order to calculate the X-ray luminosities. We find 56 stars to be probable new cluster members, presumably weak line T Tauri stars, because of their X-ray properties. Since previously 49 Halpha emission line stars and 17 proper motion members were known, this nearly doubles the number of known member stars in IC348.

The early type (B5 - F5) stars do not appear to be intrinsic X-ray emitters. The late type stars display similar X-ray properties as those in other star forming regions. The weak line T Tauri stars seem to be stronger X-ray emitters than the classical T Tauri stars, but this difference may be caused by a selection effect. The total integrated X-ray luminosity in IC348 is at least 1.6 x 10^32 erg/sec in the ROSAT band (0.1 - 2.4 keV). The possible influence of the X-radiation on the ionization state of the cloud and on its further evolution is briefly discussed.

We report the detection of several large X-ray flares in IC348 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 variability on long or short time scales.

View some ROSAT images of IC348

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