We present a spectropolarimetric study of two weak-line T Tauri stars (wTTSs), TWA 6, and TWA 8A, as part of the MaTYSSE (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) programme. Both stars display significant Zeeman signatures that we have modelled using Zeeman Doppler Imaging (ZDI). The magnetic field of TWA 6 is split equally between poloidal and toroidal components, with the largest fraction of energy in higher order modes, with a total unsigned flux of 840 G, and a poloidal component tilted 35° from the rotation axis. TWA 8A has a 70 per cent poloidal field, with most of the energy in higher order modes, with an unsigned flux of 1.4 kG (with a magnetic filling factor of 0.2), and a poloidal field tilted 20° from the rotation axis. Spectral fitting of the very strong field in TWA 8A (in individual lines, simultaneously for Stokes I and V) yielded a mean magnetic field strength of 6.0 ± 0.5 kG. The higher field strengths recovered from spectral fitting suggests that a significant proportion of magnetic energy lies in small-scale fields that are unresolved by ZDI. So far, wTTSs in MaTYSSE appear to show that the poloidal-field axisymmetry correlates with the magnetic field strength. Moreover, it appears that classical T Tauri stars (cTTSs) and wTTSs are mostly poloidal and axisymmetric when mostly convective and cooler than ̃4300 K, with hotter stars being less axisymmetric and poloidal, regardless of internal structure....
|Number of pages||24|
|Journal||Monthly Notices of the Royal Astronomical Society|
|Publication status||Published - 11 Apr 2019|
- Magnetic fields
- Stars: formation
- Stars: imaging
- Stars: individual: TWA 6
- Stars: individual: TWA 8A
- Techniques: polarimetric
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science
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- Physics - Lecturer in Astrophysics (joint appointment: 50% Mathematics 50% Physics)