Time Lag between Accretion and Wind Events in the T Tauri Star RY Tau

TL;DR

This study monitors RY Tau over 220 nights, revealing a 20-day variability cycle in accretion and wind flows with a 2-day lag, linked to the star's magnetic tilt and wind geometry.

Contribution

It provides the first detailed analysis of the time lag between accretion and wind events in RY Tau, connecting spectral variability to magnetic and geometric factors.

Findings

Wind and accretion flows vary on ~20-day timescales.

A 2-day lag exists between increased accretion and wind absorption.

Magnetic tilt influences the observed flow variability.

Abstract

The results of spectroscopic and photometric monitoring of the classical T Tauri star RY Tau are presented. The observation series span 220 nights from 2013 to 2024. During the observation period, the star's brightness varied within the range of V=9-11 mag. The rotation axis of the "star + accretion disk" system is tilted at a large angle, so the line of sight intersects the wind region and accreting flows in the star's magnetosphere. Variability in the short-wavelength wing of the Halpha emission line and the profile of the D NaI resonance doublet are analyzed. It is shown that the wind and accretion flows vary on a time scale of approximately 20 days. When the predominant flow direction changes, a time lag is observed: initially, accretion increases, and after two days, absorption in the line-of-sight wind decreases. It is concluded that the spectral line profiles are formed in the magnetospheric accretion flows and the conical wind originating from the boundary of the star's magnetosphere. The time lag is determined by the tilt of the magnetic dipole and the opening angle of the conical wind. It is assumed that RY Tau operates in an unstable propeller mode, and fluctuations in the accretion and wind flows are caused by density waves in the accretion disk.