2020ApJ...898..109F

We present high-resolution H- and K-band spectroscopic observations of the archetypal T Tauri star T Tau North. Synthetic spectral modeling is used to derive the K-band temperature, surface gravity, magnetic field strength, and rotational velocity for this star. The K-band spectroscopic temperature measured is T_K - band_=3976±90K, which is ∼1000K cooler than the temperature measured from optical observations. Our K-band temperature measurement for T Tau N is confirmed using equivalent-width line ratio versus temperature relations in the H band, from which a T_H - band_=4085±155K is derived. This optical versus IR temperature difference is interpreted as cool or hot spots, or both, covering a significant part of the surface of T Tau N. The gravity derived for T Tau N, logg=3.45±0.14, is lower than the gravity of nearly every other star in a sample of 24 classical T Tauri stars in Taurus. Combining these temperature and gravity results with magnetic stellar evolutionary models, we find the age of T Tau N to be less than 1 Myr old. These results suggest that T Tau N is in an earlier evolutionary stage than most classical T Tauri stars in Taurus, arguing that it is a protostar ejected from the embedded southern binary system shortly after its formation.