EDP Sciences
Free access
Volume 403, Number 1, May III 2003
Page(s) 187 - 203
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20030305

A&A 403, 187-203 (2003)
DOI: 10.1051/0004-6361:20030305

An XMM-Newton-based X-ray survey of pre-main sequence stellar emission in the L1551 star-forming complex

F. Favata1, G. Giardino1, G. Micela2, S. Sciortino2 and F. Damiani2

1  Astrophysics Division - Research and Science Support Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
2  INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy

(Received 11 November 2002 / Accepted 21 February 2003 )

We present a study of the X-ray sources present in the nearby L1551 star forming region, based on a deep XMM-Newton observation complemented with Chandra data for the brightest sources. Most known pre-main sequence stars in the region have been detected, most of them with sufficient statistics to allow a detailed study of the temporal and spectral characteristics of their X-ray emission. Significant temporal (and spectral) variability on both short and long time scales is visible for most of the stars. In particular XZ Tau shows large-amplitude variations on time scales of several hours with large changes in the intervening absorption, suggestive of the X-ray emission being eclipsed by the accretion stream (and thus of the X-ray emission being partly or totally accretion-induced). The coronal metal abundance of the WTTS sources is clustered around $Z \simeq 0.2$, while the CTTS sources span almost two orders of magnitudes in coronal Z, even though the photospheric abundance of all stars in the L1551 is likely to be very similar. Some individual elements (notably Ne) appear to be systematically enhanced with respect to Fe in the WTTS stars. The significant differences between the spectral and temporal characteristics of the CTTS and WTTS populations suggest that a different emission mechanism is (at least partly) responsible for the X-ray emission of the two types of stars.

Key words: ISM: individual objects: L1551 -- stars: formation -- stars: pre-main sequence -- X-rays: stars

Offprint request: F. Favata, Fabio.Favata@rssd.esa.int

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