The surface magnetic activity of the weak-line T Tauri stars TWA 7 and TWA 25
Article
Article Title | The surface magnetic activity of the weak-line T Tauri stars TWA 7 and TWA 25 |
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ERA Journal ID | 1074 |
Article Category | Article |
Authors | Nicholson, B. A. (Author), Hussain, G. (Author), Donati, J.-F. (Author), Wright, D. (Author), Folsom, C.P. (Author), Wittenmyer, R. (Author), Okumura, J. (Author) and Carter, B.D. (Author) |
Journal Title | Monthly Notices of the Royal Astronomical Society |
Journal Citation | 504 (2), pp. 2461-2473 |
Number of Pages | 17 |
Year | 2021 |
Publisher | Oxford University Press |
Place of Publication | United Kingdom |
ISSN | 0035-8711 |
1365-2966 | |
Digital Object Identifier (DOI) | https://doi.org/10.1093/mnras/stab879 |
Web Address (URL) | https://academic.oup.com/mnras/article/504/2/2461/6189719 |
Abstract | We present an analysis of spectropolarimetric observations of the low-mass weak-line T Tauri stars TWA 25 and TWA 7. The large-scale surface magnetic fields have been reconstructed for both stars using the technique of Zeeman Doppler imaging. Our surface maps reveal predominantly toroidal and non-axisymmetric fields for both stars. These maps reinforce the wide range of surface magnetic fields that have been recovered, particularly in pre-main sequence stars that have stopped accreting from the (now depleted) central regions of their discs. We reconstruct the large scale surface brightness distributions for both stars, and use these reconstructions to filter out the activity-induced radial velocity jitter, reducing the RMS of the radial velocity variations from 495 to 32 ms(-1) for TWA 25, and from 127 to 36 ms(-1) for TWA 7, ruling out the presence of close-in giant planets for both stars. The TWA 7 radial velocities provide an example of a case where the activity-induced radial velocity variations mimic a Keplerian signal that is uncorrelated with the spectral activity indices. This shows the usefulness of longitudinal magnetic field measurements in identifying activity-induced radial velocity variations. |
Keywords | magnetic fields; techniques: polarimetric; stars: formation; stars:; imaging; stars: individual: TWA 7; stars: individual: TWA 25; Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Earth and; Planetary Astrophysics |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
Byline Affiliations | University of Oxford, United Kingdom |
European Southern Observatory (ESO), Germany | |
University of Toulouse, France | |
Centre for Astrophysics | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q6x87/the-surface-magnetic-activity-of-the-weak-line-t-tauri-stars-twa-7-and-twa-25
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