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

TL;DR

This study analyzes long-term variability in jets from three T Tauri stars using near-infrared observations, revealing irregular knot ejections, velocity differences, and brightness decay, which inform models of jet dynamics and star-disk interactions.

Contribution

It provides the first detailed long-term observational analysis of jet knot variability and velocities in RW Aur A, RY Tau, and DG Tau, highlighting differences over decades.

Findings

Jets contain knots with velocities of 70-240 km/s.

Knots' sizes increase and brightness decreases over time.

Significant velocity differences observed in DG Tau between 1985-2008 and 2008-2021.

Abstract

We present Gemini-NIFS, VLT-SINFONI and Keck-OSIRIS observations of near-infrared [Fe II] emission associated with the well-studied jets from three active T Tauri stars; RW Aur A, RY Tau and DG Tau taken from 2012-2021. We primarily covered the redshifted jet from RW Aur A, and the blueshifted jets from RY Tau and DG Tau, to investigate long-term time variabilities 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, ejected from the star with different velocities and at irregular time intervals. Via comparison with literature, we identify significant differences in tangential velocities for the DG Tau jet between 1985-2008 and 2008-2021. The sizes of the individual knots appear to increase with time, and in turn, their peak brightnesses in the 1.644-micron emission decreased up to a factor of ~30 during the epochs of our observations. A variety of the decay timescales measured in the [Fe II] 1.644 micron emission can be attributed to different pre-shock conditions if the moving knots are unresolved shocks. However, our data do not exclude the possibility that these knots are due to non-uniform 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 are necessary to better understand their physical nature.