SCYON Abstract

Received on January 9 2006

Deep X-ray survey of the young open cluster NGC 2516 with XMM-Newton

AuthorsI. Pillitteri (1,2)
G. Micela (2)
F. Damiani (2)
S. Sciortino (2)
Affiliation
1- DSFA, Univ. degli Studi di Palermo, Piazza del Parlamento 1, 90134 Palermo, ITALY;
2- INAF - Osserv. Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, ITALY
Accepted byAstronomy & Astrophysics
Contactpilli@astropa.unipa.it
URLhttp://www.astropa.unipa.it/Library/preprint.html
Links NGC 2516

Abstract

We report on a deep X-ray survey of the young (~ 140 Myr), rich open cluster NGC 2516 obtained with the EPIC camera on board the XMM-Newton satellite. By combining data from six observations, a high sensitivity, greater than a factor 5 with respect to recent Chandra observations, has been achieved. Kaplan-Meier estimators of the cumulative X-ray luminosity distribution are built, statistically corrected for non members contaminants and compared to those of the nearly coeval Pleiades. The EPIC spectra of the X-ray brightest stars are fitted using optically thin model plasma with one or two thermal components. We detected 431 X-ray sources and 234 of them have as optical counterparts cluster stars spanning the entire NGC 2516 Main Sequence. On the basis of X-ray emission and optical photometry, we indicate 20 new candidate members of the cluster; at the same time we find 49 X-ray sources without known optical or infrared counterpart. The X-ray luminosities of cluster stars span the range log Lx (erg/s) = 28.4 - 30.8. The representative temperatures span the 0.3 - 0.6 keV (3.5 - 8 MK) range for the cool component and 1.0 - 2.0 keV (12 - 23 MK) for the hot one; similar values are found in other young open clusters like the Pleiades, IC 2391, and Blanco 1. While no significant differences are found in X-ray spectra, NGC 2516 solar type stars are definitely less luminous in X-rays than the nearly coeval Pleiades. The comparison with a previous ROSAT survey evidence the lack of variability amplitudes larger than a factor 2 in solar type stars in a ~11 yr time scale of the cluster and thus activity cycles like in the Sun are probably absent or different by period and amplitude in young stars.