Orbital parameters and activity of ZZ Tau – a low-mass young binary with circumbinary disc

Abstract

ABSTRACT We present the results of our new observations of the young binary ZZ Tau with a circumbinary disc. The system was found to consist of two coeval (age < 2 Myr) classical T Tauri stars with the total mass 0.86 ± 0.09 M⊙, orbital period 46.8 ± 0.8 yr, semimajor axis 88.2 ± 2.1 mas, eccentricity 0.58 ± 0.02, and the orbital inclination 123${_{.}^{\circ}}$8 ± 1${_{.}^{\circ}}$0. The accretion rate of ZZ Tau A and ZZ Tau B is approximately 7 × 10−10 and 2 × 10−10 M⊙ yr−1, respectively. No correlation was found between the long-term photometric variability of ZZ Tau and orbital position of its components. The periodic light variations with P = 4.171 ± 0.002 d were observed in the BVRI bands presumably connected with an accretion (hot) spot on the surface of the primary (ZZ Tau A). At the same time, no periodicity was observed in the U band nor in the emission line profile variations probably, due to the significant contribution of ZZ Tau B’s emission, which dominates shortward of λ ≈ 0.4 $\mu$m. We argue that the extinction in the direction to the primary is noticeably larger than that to the secondary. It appeared that the rotation axis of the primary is inclined to the line of sight by ≈31° ± 4°. We also concluded that ZZ Tau is the source of a CO molecular outflow; however, ZZ Tau IRS rather than ZZ Tau is the source of the Herbig–Haro object HH393.