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A&A 468, 477-484 (2007)
DOI: 10.1051/0004-6361:20066551
Statistics of superimposed flares in the Taurus molecular cloud
K. Arzner1, M. Güdel1, K. Briggs1, A. Telleschi1, and M. Audard21 Paul Scherrer Institut, CH 5232 Villigen, Switzerland
e-mail: arzner@astro.phys.ethz.ch
2 Columbia Astrophysics Laboratory, 550 West 120th St., MC 5247, New York, NY 10027, USA
(Received 12 October 2006 / Accepted 19 February 2007)
Abstract
Context.Stochastically occurring flares provide a possible mechanism of coronal heating in magnetically active stars
such as T Tauri objects in star-forming regions.
Aims.We investigate the statistics of stellar X-ray light curves from the XMM-Newton Extended
Survey of the Taurus Molecular Cloud (XEST).
Methods.To this end, the light curve is modeled as superimposed flares occurring at
random times and with random amplitudes. The flare shape is estimated non-parametrically from
the observations, while the flare amplitude distribution is modeled as a truncated power law,
and the flare times are assumed as uniformly distributed. From these model assumptions, predictions
on the binned counts are derived and compared with the observations.
Results.From a sample of 22 XEST observations matching the above model assumptions we find that the
majority of cases have flare amplitude distributions with slopes steeper than two. This favours
the role of small flares in coronal heating for 5 targets, of which, however,
4 are foreground or background main-sequence stars.
Key words: methods: statistical -- stars: coronae -- stars: pre-main sequence -- X-rays: stars
© ESO 2007