ZZ Tau IRS: a Low Mass UX Ori Type Star with Strong Wind

Abstract

The results of photometric, polarimetric, and spectroscopic observations of the young star ZZ Tau IRS in the visible and near-infrared bands are presented. Against the continuum of an M spectral type star about 50 emission lines of allowed (H I, He I, Na I, S II) and forbidden (O I, O II, O III, N I, N II, S II, Ca II, Fe II, Ni II) transitions were identified. It was found that from the autumn of 2020 to the beginning of 2023, the brightness of the star in the visible region decreased \((\Delta I\approx 1\overset{\textrm{m}}{.}5\)) and then began to return to the initial level. As the visible brightness of the star declined, its color indices decreased in the visible region, but increased in the near-IR bands. At light minimum, the degree of polarization in the \(I\) band reached approx 13\(\%\), and the equivalent widths of, e.g., the H\(\alpha\) and [S II] \(\lambda\) 6731 lines increased to 376 and 79 \({{\text{\AA}}^{\circ}}\), respectively. Arguments are given in favor of ZZ Tau IRS being a UX Ori type star, and its variability being due to eclipses by dust clouds, which are inhomogeneities in the dusty disk wind. Forbidden lines are formed both in the disk wind and in the jet, the axis of what is oriented along \(PA=61^{\circ}\pm 3^{\circ}\). The jet mass-loss rate exceeds \(5\times 10^{-10}M_{\odot}\) yr\({}^{-1}\), what is abnormally large for a star with a mass less than \(0.3M_{\odot}\). Apparently, the disk wind of ZZ Tau IRS is not axially symmetric, probably due to the azimuthal asymmetry of the protoplanetary disk found earlier from ALMA observations.