Orbital Motion, Variability, and Masses in the T Tauri Triple System

TL;DR

This study uses adaptive optics imaging to determine the orbital motion and dynamical masses of the T Tauri triple system, revealing mass estimates and variability patterns that improve understanding of young stellar objects.

Contribution

First dynamical mass measurements of T Tauri Sa and Sb using Gaia distance and orbital modeling, with ongoing observations to refine these estimates.

Findings

Dynamical masses: M_Sa = 2.05 +/- 0.14 Msun, M_Sb = 0.43 +/- 0.06 Msun

T Tau N has a mass of approximately 2 Msun, similar to T Tau Sa

Significant variability observed in T Tau Sa and Sb in the K-band

Abstract

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 +/- 0.14 Msun and M_Sb = 0.43 +/- 0.06 Msun. 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 ~ 2 Msun 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 +/- 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.