Observational clues for a role of circumstellar accretion in PMS X-ray activity
INAF - Osservatorio Astronomico di Palermo Giuseppe S. Vaiana, Palazzo dei Normanni, 90134 Palermo, Italy e-mail: firstname.lastname@example.org;email@example.com
Corresponding author: E. Flaccomio, firstname.lastname@example.org
Accepted: 9 October 2002
We revisit the published analyses of ROSAT X-ray observations of the star forming regions NGC 2264 and Chamaeleon I (∼3 and ∼5 Myr old respectively) in the light of newly published optical data. At odds with previous results on Chamaeleon I members, we find that low mass stars in both regions have near-saturated emission levels. Similarly to what previously found in the Orion Nebula Cluster, Weak Line T-Tauri Stars in NGC 2264 and in the Chamaeleon I cloud have higher X-ray activity levels respect to Classical T Tauri Stars, arguing in favor of a role of the disk and/or accretion in determining X-ray emission.
Key words: stars: pre-main sequence / X-rays: stars / accretion, accretion disks / open clusters and associations: individual: Orion Nebula Cluster, NGC 2264, Chamaeleon I
© ESO, 2003