EDP Sciences
Free access
Issue
A&A
Volume 430, Number 1, January IV 2005
Page(s) 287 - 301
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20041525


A&A 430, 287-301 (2005)
DOI: 10.1051/0004-6361:20041525

X-ray spectral and timing characteristics of the stars in the young open cluster IC 2391

A. Marino1, 2, G. Micela2, G. Peres1, I. Pillitteri1 and S. Sciortino2

1  Dipartimento di Scienze Fisiche & Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
    e-mail: marino@astropa.unipa.it
2  INAF - Osservatorio Astronomico di Palermo Piazza del Parlamento 1, 90134 Palermo, Italy

(Received 24 June 2004 / Accepted 16 September 2004 )

Abstract
We present X-ray spectral and timing analysis of members of the young open cluster IC 2391 observed with the XMM-Newton observatory. We detected 99 X-ray sources by analysing the summed data obtained from MOS1, MOS2 and pn detectors of the EPIC camera; 24 of them are members, or probable members, of the cluster. Stars of all spectral types have been detected, from the early-types to the late-M dwarfs.

Despite the capability of the instrument to recognize up to 3 thermal components, the X-ray spectra of the G, K and M members of the cluster are well described with two thermal components (at $kT_1 \sim 0.3$-0.5 keV and $kT_2 \sim 1.0$-1.2 keV respectively) while the X-ray spectra of F members require only a softer 1-T model.

The Kolmogorov-Smirnov test applied to the X-ray photon time series shows that approximately 46% of the members of IC 2391 are variable with a confidence level >99%. The comparison of our data with those obtained with ROSAT/PSPC, nine years earlier, and ROSAT/HRI, seven years earlier, shows that there is no evidence of significant  variability on these time scales, suggesting that long-term variations due to activity cycles similar to that on the Sun are not common, if present at all, among these young stars.


Key words: X-ray: stars -- stars: coronae -- stars: activity -- stars: early-type -- stars: late-type -- Galaxy: open clusters and associations: individual: IC 2391

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