Uncovering a new group of T Tauri stars in the Taurus-Auriga molecular complex from Gaia and GALEX data

Abstract

Context. Determining a complete census of young stars in any star forming region is a challenge even for the nearest and best-observed molecular clouds, such as Taurus-Auriga (TAMC). Deep surveys at infrared (IR) and X-ray wavelengths and astrometric surveys using Gaia DR2 and DR3 have been carried out to detect the sparse population and constrain the low-mass end of the initial mass function. These compilations have resulted in lists of more than 500 sources, including reliable members of the association and candidates. The astrometric information provided by the Gaia mission has proven to be of fundamental importance in evaluating these candidates. Aims. In the present work, we examine the list of 63 candidate T Tauri star (TTS) in the TAMC identified by their ultraviolet (UV) and IR colours measured from data obtained by the Galaxy Evolution Explorer all sky survey (GALEX-AIS) and the Two Microns All Sky Survey (2MASS), respectively. These sources have not been included in previous studies and the objectives of this work are twofold: to evaluate whether or not they are pre-main sequence (PMS) stars and to evaluate the true potentials of the UV-IR colour–colour diagram to detect PMS stars in wide fields. Methods. We retrieved the kinematic properties and the parallax of these sources from the Gaia DR3 catalogue and used them to evaluate their membership probability. We tested several classification algorithms to search for the kinematical groups, but made the final classification with k-means++ algorithms. We evaluated membership probability by applying logistic regression. In addition, we used spectroscopic information available in the archive of the Large Sky Area Multi Object Fiber Spectroscopic Telescope (LAMOST) to ascertain their PMS nature when available. Results. About 20% of the candidates share the kinematics of the TAMC members. Among them, HD 281691 is a G8-type field star located in front of the cloud and HO Aur is likely a halo star given the very low metallicity provided by Gaia. The remaining sources included three known PMS stars (HD 30171, V600 Aur and J04590305+3003004), two previously unknown accreting M-type stars (J04510713+1708468 and J05240794+2542438), and five additional sources that are very likely PMS stars. Most of these new sources are concentrated at low galactic latitudes over the Auriga-Perseus region.