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 \pm 0.14 M _ { \odot } and M _ { Sb } = 0.43 \pm 0.06 M _ { \odot } .
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 \sim 2 M _ { \odot } for T Tau N , suggesting that T Tau N is similar in mass to T Tau Sa .
Narrow-band infrared photometry shows that T Tau N remained relatively constant between late 2017 and early 2019 with an average value of K = 5.54 \pm 0.07 mag .
Using T Tau N to calibrate relative flux measurements since 2015 , we found that T Tau Sa varied dramatically between 7.0 to 8.8 mag in the K -band over timescales of a few months , while T Tau Sb faded steadily from 8.5 to 11.1 mag in the K -band .
Over the 27 year orbital period of the T Tau S binary , both components have shown 3–4 magnitudes of variability in the K -band , relative to T Tau N .