Nonradial and nonpolytropic astrophysical outflows. XI. Simulations of the circumstellar environment of RY Tau

TL;DR

This study uses 2.5D magneto-hydrodynamical simulations with analytical solutions to model RY Tau's circumstellar environment, revealing stable outflows and episodic ejections consistent with observations of its variable outflow stages.

Contribution

It introduces a novel simulation approach combining analytical self-similar solutions with modified initial conditions to study RY Tau's outflow behavior.

Findings

Steady state achieved in a few stellar rotations.

Two outflow behaviors similar to RY Tau's observed stages.

Mass loss to accretion ratio matches observational data.

Abstract

Context. There are recent observational evidences that RY Tau may present two different outflow stages, a quiescent one and a more active one. We try to model that phenomenon. Aims. We have performed new 2.5D magneto-hydrodynamical simulations of the possible accretion-outflow environment of RY Tau based on analytical solutions to reduce the relaxation time. Methods. We used as initial conditions the analytical self-similar solution we used to model the RY Tau micro jet. In the closed field line region of the magnetosphere we have reversed the direction of the flow and increased the accretion rate by increasing the density and the velocity. We have also implemented the heating rate and adjusted it according to the velocity of the flow. The accretion disk is treated as a boundary condition. Results. The simulations show that the stellar jet and the accreting magnetosphere attain a steady state in only a few stellar rotations, confirming the robustness and stability of self-similar solutions. Additionally, two types of behavior were observed similar to the one observed in RY Tau. Either the steady stellar outflow and magnetospheric inflow are separated by a low static force free region or the interaction between the stellar jet and the magnetospheric accretion creates coronal episodic mass ejections originating from the disk and bouncing back onto the star. Conclusions. The ratio of mass loss rate to mass accretion rate that coincides with the change of behaviour observed in RY Tau, lays within the range of ratios that have been measured during the period of the micro jet initial analysis.