Unstable magnetospheric accretion on the T Tauri star TW Hya
Abstract
In this paper, we present new spectropolarimetric and velocimetric observations of the prototypical classical T Tauri star TW Hya obtained with SPIRou at the Canada-France-Hawaii Telescope, expanding our previous monitoring over two new seasons (2024 and 2025). We confirm that the large-scale magnetic field of TW Hya varied with time and find that it showed fluctuations on a timescale of about a year in addition to the longer term variations outlined in the previous study. Using Zeeman-Doppler imaging, we find that the large-scale field of TW Hya mostly consists of a poloidal dipole of mean polar strength 0.83 kG, inclined at an average 17° to the rotation axis. We also find that the radial velocities of TW Hya, once fully filtered from telluric contamination, were dominated by rotational modulation induced by activity, with residuals of 32 m s −1 rms. No signal from a putative close-in planet is found, with an upper limit on the planet mass ranging from 0.33 to 0.98 M for distances of 0.053 to 0.41 au from the central star. Emission lines indicate that the mass-accretion rate was equal to 10 −8.33±0.20 M ⊙ yr −1 on average, with peak-to-peak fluctuations by a factor of ≃5 from season to season. This confirms that accretion onto TW Hya is unstable, with the magnetospheric gap carved by the large-scale field at the center of the disk extending to no further than 33–40% of the corotation radius on average, where the disk’s Keplerian angular velocity equals the rotation rate at the stellar surface.
Related
- 3D simulations of magnetospheric accretion in T Tauri stars I. Disk truncation, stellar torques, and application to observations
- 3D simulations of magnetospheric accretion in T Tauri stars: I. Disk truncation, stellar torques, and application to observations
- Ultraviolet accretion continua reveal a transition in T Tauri magnetic topology
- Preparing for the Early eVolution Explorer: Photometric Diagnostics of Magnetospheric Accretion Geometry in Young Stellar Objects
- Impact of accretion variability on the CO emission of a disk around a very low-mass star with JWST
BibTeX
@article{donati2026unstable,
title = {{Unstable magnetospheric accretion on the T Tauri star TW Hya}},
author = {J.-F. Donati and P. Cristofari and C. Moutou and A. Carmona and A. Lavail and J. Bouvier and K. Perraut and S. Alencar and M. Audard and K. Grankin and F. Ménard and M. Takami},
journal = {Astronomy \& Astrophysics - A\&A},
year = {2026},
month = sep,
doi = {10.1051/0004-6361/202661267},
url = {https://hal.science/hal-05803568v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Unstable magnetospheric accretion on the T Tauri star TW Hya
AU - J.-F. Donati
AU - P. Cristofari
AU - C. Moutou
AU - A. Carmona
AU - A. Lavail
AU - J. Bouvier
AU - K. Perraut
AU - S. Alencar
AU - M. Audard
AU - K. Grankin
AU - F. Ménard
AU - M. Takami
PY - 2026
DA - 2026/09/22
JO - Astronomy & Astrophysics - A&A
DO - 10.1051/0004-6361/202661267
UR - https://hal.science/hal-05803568v1
AB - In this paper, we present new spectropolarimetric and velocimetric observations of the prototypical classical T Tauri star TW Hya obtained with SPIRou at the Canada-France-Hawaii Telescope, expanding our previous monitoring over two new seasons (2024 and 2025). We confirm that the large-scale magnetic field of TW Hya varied with time and find that it showed fluctuations on a timescale of about a year in addition to the longer term variations outlined in the previous study. Using Zeeman-Doppler imaging, we find that the large-scale field of TW Hya mostly consists of a poloidal dipole of mean polar strength 0.83 kG, inclined at an average 17° to the rotation axis. We also find that the radial velocities of TW Hya, once fully filtered from telluric contamination, were dominated by rotational modulation induced by activity, with residuals of 32 m s −1 rms. No signal from a putative close-in planet is found, with an upper limit on the planet mass ranging from 0.33 to 0.98 M for distances of 0.053 to 0.41 au from the central star. Emission lines indicate that the mass-accretion rate was equal to 10 −8.33±0.20 M ⊙ yr −1 on average, with peak-to-peak fluctuations by a factor of ≃5 from season to season. This confirms that accretion onto TW Hya is unstable, with the magnetospheric gap carved by the large-scale field at the center of the disk extending to no further than 33–40% of the corotation radius on average, where the disk’s Keplerian angular velocity equals the rotation rate at the stellar surface.
SN - 0004-6361
SN - 1432-0746
ER -