Time-variable Jet Ejections from RW Aur A, RY Tau, and DG Tau*

We present Gemini-NIFS, Very Large Telescope-SINFONI, and Keck-OSIRIS observations of near-IR [Fe ii] emission that are associated with well-studied jets from three active T Tauri stars-RW Aur A, RY Tau, and DG Tau-taken from 2012 to 2021. We primarily cover the redshifted jet from RW Aur A and the blueshifted jets from RY Tau and DG Tau, in order to investigate long-term time variabilities that are potentially related to the activities of mass accretion and/or the stellar magnetic fields. All of these jets consist of several moving knots, with tangential velocities of 70-240 km s(-1), which were ejected from the star with different velocities and at irregular time intervals. Via comparisons with the literature, we identify significant differences in the tangential velocities between 1985-2008 and 2008-2021 for the DG Tau jet. The sizes of the individual knots appear to increase with time, and, in turn, their peak brightnesses in the 1.644 mu m emission decreased by up to a factor of similar to 30 during the epochs of our observations. The variety of decay timescales measured in the [Fe ii] 1.644 mu m emission could be attributed to different preshock conditions should the moving knots be unresolved shocks. However, our data do not exclude the possibility that these knots are due to nonuniform density/temperature distributions with another heating mechanism, or, in some cases, due to stationary shocks without proper motions. Spatially resolved observations of these knots with significantly higher angular resolutions will be necessary to better understand their physical nature.

Automated summary

We present observations of near-IR [Fe ii] emission from the jets of three active T Tauri stars, RW Aur A, RY Tau, and DG Tau, taken from 2012 to 2021. The velocities and sizes of the jets vary over time, and significant differences in velocities were found in the DG Tau jet between two time periods. The brightness of the individual knots in the emission decreased during our observations. Higher angular resolution observations are needed to better understand the physical nature of these knots.