New pre-main sequence candidates in the Taurus-Auriga star forming region^*

¹ Dipartimento di Scienze Fisiche ed Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy e-mail: scelsi@oapa.astropa.unipa.it
² INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
³ Paul Scherrer Institut, Würenlingen and Villigen, 5232 Villigen PSI, Switzerland
⁴ Laboratoire d'Astrophysique de Grenoble, Université Joseph-Fourier, 414 rue de la Piscine, 38041 Grenoble Cedex, France
⁵ Columbia Astrophysics Laboratory, Mail Code 5247, 550 West 120th Street, New York, NY 10027, USA
⁶ INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

Received: 4 May 2006
Accepted: 3 August 2006

Abstract

Aims.We have studied the X-ray source population of the Taurus Molecular Cloud (TMC) to search for new members of the Taurus-Auriga star forming region.

Methods.Candidate members have been selected among the X-ray sources detected in 24 fields of the XMM-Newton Extended Survey of the Taurus Molecular Cloud, having an IR counterpart in the 2MASS catalog, based on color–magnitude and color–color diagrams. Their X-ray spectral properties have been compared with those of known members and other X-ray sources in the same fields but without a NIR counterpart. A search for flare-like variability in the time series of all new candidates and the analysis of the X-ray spectra of the brightest candidates have been used to identify sources with a high probability of membership.

Results.We have found that 347 of 1909 detected X-ray sources have an infrared counterpart in the 2MASS catalogue. Among them, we have selected 57 sources that are consistent with being new pre-main sequence star candidates at the distance of the Taurus-Auriga star forming region; the X-ray spectral properties of this sample are, on the whole, similar to the properties of known TMC members and different from those of X-ray sources without an IR counterpart, most of which are likely to be of extragalactic origin. For 12 such candidates, the likelihood of membership is very high, based on the relatively high plasma temperatures derived from their X-ray spectra and/or the observation of powerful flares in their light curves.