Magnetic torques on T Tauri stars: accreting vs. non-accreting systems
Journal
Date Issued
2020
Author(s)
Abstract
Classical T Tauri stars (CTTs) magnetically interact with their surrounding
disks, a process that is thought to regulate their rotational evolution. In
this work, we compute torques acting onto the stellar surface of CTTs arising
from different accreting (accretion funnels) and ejecting (stellar winds and
magnetospheric ejections) flow components. Furthermore, we compare the magnetic
braking due to stellar winds in two different systems: isolated and accreting
stars. 2.5D magnetohydrodynamic, time-dependent, axisymmetric simulations are
employed. For both systems the stellar wind is thermally driven. In the
star-disk-interaction (SDI) simulations the accretion disk is Keplerian,
viscous, and resistive. Two series of simulations are presented, one for each
system. We find that in classical T Tauri systems the presence of
magnetospheric ejections confines the stellar-wind expansion, resulting in an
hourglass-shaped geometry of the outflow. In addition, the formation of the
accretion columns modifies the amount of open magnetic flux exploited by the
stellar wind. These effects have a strong impact on the stellar wind properties
and we show that the stellar-wind braking is more efficient in the
star-disk-interacting systems than in the isolated ones. We also derive torque
scalings, over a wide range of magnetic field strengths, for each flow
component in a SDI system that directly applies a torque on the stellar
surface. In all the performed SDI simulations the stellar wind extracts less
than 2% of the mass accretion rate and the disk is truncated up to 66% of the
corotation radius. All the simulations show a net spin-up torque. In order to
achieve a stellar-spin equilibrium we need either more massive stellar winds or
disks being truncated closer to the corotation radius, which increases the
torque efficiency by the magnetospheric ejections.
Volume
643
Start page
A129
Issn Identifier
0004-6361
Ads BibCode
2020A&A...643A.129P
Rights
open.access
File(s)![Thumbnail Image]()
![Thumbnail Image]()
Loading...
Name
PantolmosA&Apostprint2020.pdf
Size
5.25 MB
Format
Adobe PDF
Checksum (MD5)
849369681bdd25f633169b8fcdfef201
Loading...
Name
PantolmosA&A2020.pdf
Description
PDF editoriale
Size
6.49 MB
Format
Adobe PDF
Checksum (MD5)
317de6cecf6ba17b3233c6e709a5b9fd