Spectroscopic validation of Gaia-selected T Tauri candidates in Taurus–Auriga: contamination and binary accretion properties

Abstract

We present high-resolution optical spectroscopy of a sample of candidate and known T Tauri stars in the Taurus–Auriga molecular cloud, with the aim of assessing their pre-main-sequence nature and characterizing their accretion and outflow properties. Among five poorly characterized candidates selected on the basis of UV–IR photometry and Gaia astrometry, two are confirmed as pre-main-sequence stars through the detection of Li I λ6708 absorption and Hα emission, whereas the remaining three are identified as more evolved field stars lacking spectroscopic signatures of youth. The two confirmed young stars are classified as weak-line T Tauri stars. One of them, 2MASS J05005485+3229168, is resolved by Gaia as a ~1.4″ binary, highlighting the presence of non-accreting binary systems that may be underrepresented in spectroscopic samples. We also present spatially resolved spectroscopy of the GZ Aur system, showing that both components are classical T Tauri stars undergoing active accretion. Strong permitted and forbidden emission lines, together with blueshifted line profiles, reveal ongoing accretion and outflow activity in both components. The two stars exhibit different levels of accretion, consistent with previous findings that accretion in wide binary systems is not necessarily synchronized. These results emphasize the importance of combining Gaia astrometry with spectroscopic diagnostics to obtain a reliable census of young stellar populations and to characterize their multiplicity, accretion, and outflow properties.