Dynamics of wind and the dusty environments in the accreting T Tauri stars RY Tauri and SU Aurigae
Classical T Tauri stars with ages of less than 10 Myr possess accretion discs. Magnetohydro-dynamic processes at the boundary between the disc and the stellar magnetosphere control the accretion and ejections gas flows. We carried out a long series of simultaneous spectroscopic and photometric observations of the classical T Tauri stars, RY Tauri and SU Aurigae, with the aim to quantify the accretion and outflow dynamics at time-scales from days to years. It is shown that dust in the disc wind is the main source of photometric variability of these stars. In RY Tau, we observed a new effect: during events of enhanced outflow, the circumstellar extinction becomes lower. The characteristic time of changes in outflow velocity and stellar brightness indicates that the obscuring dust is near the star. The outflow activity in both stars is changing on a time-scale of years. Periods of quiescence in the variability of the Hα profile were observed during the 2015-2016 period in RY Tau and during the 2016-2017 period in SU Aur. We interpret these findings in the framework of the magnetospheric accretion model, and we discuss how the global stellar magnetic field can influence the long-term variations of the outflow activity.© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society ; This research was supported by the RFBR grant 16-02-00140. It was based partly on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias, using ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOTSA. We acknowledge support from a Visitors Programme at the Department of Astronomy at Stockholm University. JFG and RMGA were supported by Fundacao para a Ciencia e a Tecnologia (FCT) through national funds (UID/FIS/04434/2013) and by FEDER through COMPETE2020 (POCI-01-0145-FEDER-007672). RMGA is supported by the fellowship PD/BD/113745/2015, under the FCT PD Program PhD::SPACE, funded by FCT (Portugal) and POPH/FSE (EC) and by CRUP through a cooperation programme (PAULIF: TC-16/17). DEM acknowledges his work as part of the research activity supported by the National Astronomical Research Institute of Thailand (NARIT), Ministry of Science and Technology of Thailand. SYuG was supported in part by the Ministry of Education and Science of Russia (the basic part of the Stateassignment, RK no. AAAA-A17-117030310283-7) and by the Act no. 211 of the Government of the Russian Federation, agreement No 02.A03.21.0006. ; Peer Reviewed