X-ray sources in regions of star formation. III - Naked T Tauri stars associated with the Taurus-Auriga complex

Abstract

The authors report results from a multispectral investigation of stellar counterparts of X-ray sources in the general region of the Taurus-Auriga star-formation complex. They discuss 28 new low-mass pre-main-sequence "naked T Tauri" stars, bringing the census of naked T Tauri stars to 44 in the Tau-Aur region. The authors discuss the optical spectra and the optical and near-IR colors. They show that these stars are basically normal stars with ages of 1 - 40×10<SUP>6</SUP>yr. There is no evidence for IR or UV excesses. Chromospheric and coronal surface fluxes are comparable to those of the most active main-sequence stars and the RS CVn systems. The authors show that the chromospheric fluxes do not increase for stellar ages &lt;10<SUP>8</SUP>yr, confirming the postulated exponential decay of stellar activity.