EDP Sciences
Free access
Volume 397, Number 2, January II 2003
Page(s) 611 - 621
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20021484

A&A 397, 611-621 (2003)
DOI: 10.1051/0004-6361:20021484

Observational clues for a role of circumstellar accretion in PMS X-ray activity

E. Flaccomio, G. Micela and S. Sciortino

INAF - Osservatorio Astronomico di Palermo Giuseppe S. Vaiana, Palazzo dei Normanni, 90134 Palermo, Italy
    e-mail: giusi@oapa.astropa.unipa.it;sciorti@oapa.astropa.unipa.it
(Received 25 June 2002 / Accepted 9 October 2002)

We revisit the published analyses of ROSAT X-ray observations of the star forming regions NGC 2264 and Chamaeleon I ( $\sim $3 and $\sim $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

Offprint request: E. Flaccomio, ettoref@oapa.astropa.unipa.it

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