SCYON Abstract

Received on September 22 2004

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

Authors	A. Marino^1,2, G. Micela², G. Peres¹, I. Pillitteri¹, S. Sciortino²
Affiliation	¹ Dipartimento di Scienze Fisiche & Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo - ITALY ² INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo - ITALY
Accepted by	Astronomy & Astrophysics
Contact	marino@astropa.unipa.it
URL
Links	IC 2391

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 instrument capability to recognize up to 3 thermal component, the X-ray spectra of the G, K and M members of the cluster are well described with two thermal components (at kT₁ ~ 0.3-0.5 keV and kT₂ ~ 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 photons 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.