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

E. V. Babina, P. P. Petrov, K. N. Grankin, S. A. Artemenko

TL;DR

This study investigates the timing between accretion and wind events in the classical T Tauri star RY Tau using 11 years of spectroscopic and photometric monitoring. By analyzing H$ abla$ and D NaI line profiles and applying time-series cross-correlation, the authors identify a ~2-day lag where accretion enhancements precede wind responses, consistent with magnetospheric accretion flows feeding a conical wind launched at the disk–magnetosphere boundary. The lag depends on the tilt of the magnetic dipole and the wind opening angle, supporting an unstable propeller regime driven by inner-disk density waves. The findings imply a causal coupling between inner-disk dynamics and wind launching, with implications for understanding mass-flow regulation in magnetized young stars and possible planet-induced disk structures.

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.

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

TL;DR

This study investigates the timing between accretion and wind events in the classical T Tauri star RY Tau using 11 years of spectroscopic and photometric monitoring. By analyzing H and D NaI line profiles and applying time-series cross-correlation, the authors identify a ~2-day lag where accretion enhancements precede wind responses, consistent with magnetospheric accretion flows feeding a conical wind launched at the disk–magnetosphere boundary. The lag depends on the tilt of the magnetic dipole and the wind opening angle, supporting an unstable propeller regime driven by inner-disk density waves. The findings imply a causal coupling between inner-disk dynamics and wind launching, with implications for understanding mass-flow regulation in magnetized young stars and possible planet-induced disk structures.

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.
Paper Structure (6 sections, 7 figures)

This paper contains 6 sections, 7 figures.

Table of Contents

  1. Introduction
  2. Observations
  3. Observation Analysis
  4. Time series cross-correlation
  5. Discussion
  6. acknowledgments

Figures (7)

  • Figure 1: Examples of NaI D (left panel) and H$\alpha$ (right panel) line profiles. Observation dates (HJD-2450000) are indicated in the upper right corner of the right panel. The H$\alpha$ line flux is given in units of 3.67·10$^{-13}$ erg cm$^{-2}$s$^{-1}$.
  • Figure 2: Profiles of the Н$\alpha$ and D NaI lines. Observation times: HJD 8734 (solid line) and 8765 (dashed line).
  • Figure 3: Variations in the star's V-band brightness, Н$\alpha$ flux, and accretion flow absorption (EW D1r) over 11 years.
  • Figure 4: Correlation between the absorption in the accreting flow (D1r) and the emission flux (Fb) in the "blue" wing of the Н$\alpha$ emission line. The dashed lines indicate the 99% confidence interval. Low Fb flux values correspond to high wind density along the line of sight. As accretion increases, the wind density decreases and the Fb flux increases.
  • Figure 5: Cross-correlation of the [HJD, D1r] and [HJD, Fb] time series with a shift of one series relative to the other within the range of -4 to +3 days. The solid line is the approximation by a third-degree polynomial. The dotted lines show the 95% confidence interval. The maximum correlation corresponds to a shift of -2 days: first, the accretion changes, then the wind changes.
  • ...and 2 more figures