Cool Stars 14 - Submitted Abstract # 168
This version created on 05 October 2006

X-ray variability of young PMS stars in Cygnus OB2


Juan Facundo Albacete Colombo, INAF-OAPA
Marilena Caramazza, INAF-OAPA
Giusi Micela, INAF-OAPA
Ettore Flaccomio, INAF-OAPA
Salvatore Sciortino, INAF-OAPA

We use a 100  ksec CHANDRA ACIS-I observation to statistically
characterize the X-ray variability of low-mass stars in the Cygnus OB2
star forming region.  X-ray variability is first tested using the
Kolmogorov-Smirnov test, obtaining that 13.4% (135/1003) of the
sources are variable with confidence level greater than 95%.  We then
employ Maximum Likelihood Blocks (Wolk et al.  2005) in order to
segment the X-ray lightcurve in intervals of 'constant' emission to
find out flares taking into account the amplitude and the
time-derivative of the source count-rate.  We find that most of the
flaring sources, with few exceptions, have hard spectra (Med.
Energy>2 keV).  We derive the energy distribution of detected flares
and compare our result with previous estimates obtained for members of
the Orion Nebula Cluster (Wolk et al.  2005) and of the Taurus
Molecular Cloud (Stelzer et al.  2006).

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