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

TL;DR

This study provides detailed orbital and activity characteristics of the young binary ZZ Tau with a circumbinary disc, revealing its orbital parameters, accretion rates, and variability patterns, and clarifying the origins of associated outflows and Herbig-Haro objects.

Contribution

First detailed orbital and activity analysis of ZZ Tau, including accretion rates, variability, and outflow origins, based on new observations.

Findings

Binary system consists of two coeval T Tauri stars with total mass 0.86 M_sun.

Orbital period is approximately 46.8 years with eccentricity 0.58.

Periodic light variation of 4.171 days linked to accretion hot spot on primary.

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 $0.86 \pm 0.09$ M$_\odot$, orbital period $46.8 \pm 0.8$ yr, semimajor axis $88.2 \pm 2.1$ mas, eccentricity $0.58 \pm 0.02$ and the orbital inclination $123.^{\rm o} 8 \pm 1.^{\rm o} 0.$ The accretion rate of ZZ Tau A and ZZ Tau B are approximately $7\times 10^{-10}$ and $2\times 10^{-10}$ M$_\odot$ 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 $P=4.171 \pm 0.002$ days was 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 $\lambda \approx 0.4\,\mu$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 $\approx 31^{\rm o} \pm 4^{\rm o}.$ We concluded also that ZZ Tau is the source of an CO molecular outflow, however, ZZ Tau IRS rather than ZZ Tau is the source of the Herbig-Haro object HH393.