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Description
We present results from adaptive optics imaging of the T Tauri triple system obtained at the Keck and Gemini Observatories in 2015-2019. We fit the orbital motion of T Tau Sb relative to Sa and model the astrometric motion of their center of mass relative to T Tau N. Using the distance measured by Gaia, we derived dynamical masses of M_Sa_=2.05{+/-}0.14M_{sun}_ and M_Sb_=0.43{+/-}0.06M_{sun}_. The precision in the masses is expected to improve with continued observations that map the motion through a complete orbital period; this is particularly important as the system approaches periastron passage in 2023. Based on published properties and recent evolutionary tracks, we estimate a mass of ~2M_{sun}_ for T Tau N, suggesting that T Tau N is similar in mass to T Tau Sa. Narrowband infrared photometry shows that T Tau N remained relatively constant between late 2017 and early 2019 with an average value of K=5.54{+/-}0.07mag. Using T Tau N to calibrate relative flux measurements since 2015, we found that T Tau Sa varied dramatically between 7.0 and 8.8mag in the K band over timescales of a few months, while T Tau Sb faded steadily from 8.5 to 11.1mag in the K band. Over the 27yr orbital period of the T Tau S binary, both components have shown 3-4mag of variability in the K band, relative to T Tau N.
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