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

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

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

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

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

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

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

International audienceContext. 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

Accretion in low-mass members of the Orion Nebula Cluster with young transition disks

International audienceContext. Although the Orion Nebula Cluster is one of the most studied clusters in the solar neighborhood, the evolution of the very low-mass members (M* < 0.25 M⊙) has not been fully addressed due to their faintness.Aims. Our goal is to verify if some young and very low-mass objects in the Orion Nebula Cluster show evidence of ongoing accretion using broadband VLT/X-shooter spectra.Methods. For each target, we determined the corresponding stellar parameters, veiling, observed Balmer jump, and accretion rates. Additionally, we searched for the existence of circumstellar disks through available on-line photometry.Results. We detected accretion activity in three young stellar objects in the Orion Nebula Cluster, two of them being in the very low-mass range. We also detected the presence of young transition disks with ages between 1 and 3.5 Myr.Key words: stars: low-mass / stars: pre-main sequence / open clusters and associations: individual: Orion Nebula Cluste