Understanding the mechanisms of mass accretion and jet ejection is one of the key issues of star formation theories. However, observational studies are hampered by the limited angular resolutions of current telescopes, which are not sufficient to resolve structure and kinematics in the jet launching region. Over the past ten years we have executed an alternative approach to tackle this important issue: that is, long-term monitoring of mass accretion and jet ejection for active young stars (RW Aur A, RY Tau, DG Tau). The executed observations include: (A) high-resolution imaging spectroscopy of [Fe II] 1.64-micron emission in extended jets using Gemini-NIFS, VLT-SINFONI and Keck-OSIRIS; (B) optical high-resolution spectroscopy at CFHT; and (C) optical photometry at the CrAO 1.3-m telescope. We have also used archival data from AAVSO to complement the photometric observations. The [Fe II] jet imaging was made to monitor time variable jet ejections from the individual stars while optical spectroscopy and photometry were executed to monitor mass accretion from the inner edge of the circumstellar disk to the star.
The above observations have revealed a possible time correlation between jet knot ejections and signatures of mass accretion for RW Aur A (Takami+ 2020, ApJ). The data have also been used to understand the nature of jet knots (Uyama+ 2022, AJ; Takami+ 2023, ApJS) and mass accretion onto the star (Takami+ 2016, ApJ). In our poster we will summarize our achievements and discoveries throughout the project.