The XMM-Newton extended survey of the Taurus molecular cloud (XEST) ^*,**

¹ Paul Scherrer Institut, Würenlingen and Villigen, 5232 Villigen PSI, Switzerland e-mail: guedel@astro.phys.ethz.ch
² Columbia Astrophysics Laboratory, Mail Code 5247, 550 West 120th Street, New York, NY 10027, USA
³ Laboratoire d'Astrophysique de Grenoble, Université Joseph Fourier - CNRS, BP 53, 38041 Grenoble Cedex, France
⁴ Department of Astronomy & Astrophysics, Penn State University, 525 Davey Lab, University Park, PA 16802, USA
⁵ INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
⁶ Spitzer Science Center, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125, USA
⁷ INAF - Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi, 5, 50125 Firenze, Italy
⁸ Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
⁹ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150 Porto, Portugal
¹⁰ Departamento de Matemática Aplicada, Faculdade de Ciêcias da Universidade do Porto, 4169 Porto, Portugal
¹¹ CASA, 389, University of Colorado, Boulder, CO 80309-0389, USA

Received: 31 May 2006
Accepted: 5 August 2006

Abstract

Context.The Taurus Molecular Cloud (TMC) is the nearest large star-forming region, prototypical for the distributed mode of low-mass star formation. Pre-main sequence stars are luminous X-ray sources, probably mostly owing to magnetic energy release.

Aims.The XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST) presented in this paper surveys the most populated ≈5 square degrees of the TMC, using the XMM-Newton X-ray observatory to study the thermal structure, variability, and long-term evolution of hot plasma, to investigate the magnetic dynamo, and to search for new potential members of the association. Many targets are also studied in the optical, and high-resolution X-ray grating spectroscopy has been obtained for selected bright sources.

Methods.The X-ray spectra have been coherently analyzed with two different thermal models (2-component thermal model, and a continuous emission measure distribution model). We present overall correlations with fundamental stellar parameters that were derived from the previous literature. A few detections from Chandra observations have been added.

Results.The present overview paper introduces the project and provides the basic results from the X-ray analysis of all sources detected in the XEST survey. Comprehensive tables summarize the stellar properties of all targets surveyed. The survey goes deeper than previous X-ray surveys of Taurus by about an order of magnitude and for the first time systematically accesses very faint and strongly absorbed TMC objects. We find a detection rate of 85% and 98% for classical and weak-line T Tau stars (CTTS resp. WTTS), and identify about half of the surveyed protostars and brown dwarfs. Overall, 136 out of 169 surveyed stellar systems are detected. We describe an X-ray luminosity vs. mass correlation, discuss the distribution of X-ray-to-bolometric luminosity ratios, and show evidence for lower X-ray luminosities in CTTS compared to WTTS. Detailed analysis (e.g., variability, rotation-activity relations, influence of accretion on X-rays) will be discussed in a series of accompanying papers.