Orbit of T Tau Ba-Bb and Mass Estimate for Its Infrared Companion

Abstract

On the basis of 17 astrometric radio and infrared position measurements almost uniformly covering an arc of 270°, an improved orbit with a period of 33 years and semimajor axis of 0104 (14.6 AU) for the T Tau Ba-Bb pair (also known as T Tau Sa-Sb) is calculated. A total system mass of 2.82 ± 0.74 M⊙ is obtained, leading to a first direct mass estimate for T Tau Ba, which is a known infrared companion (IRC), on the order of 2.2–2.3 M⊙. This estimate supports the model in which the IRC may be a young star coeval with T Tau A that suffers stronger extinction because it is experiencing an episode of enhanced accretion, possibly tied to its orbital phase. The obtained orbit is clearly distinguishable from the previous solution and therefore allows verification of the behavior of the system in the near future.