Magnetospheric accretion and spin-down of the prototypical classical T Tauri star AA Tau
From observations collected with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope (CFHT) and with the NARVAL spectropolarimeter at the Télescope Bernard Lyot (TBL), we report the detection of Zeeman signatures on the prototypical classical T Tauri star AA Tau, both in photospher...
Published in: | Monthly Notices of the Royal Astronomical Society |
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ftunivdundeepure:oai:discovery.dundee.ac.uk:publications/0193c517-3ab0-4884-90b9-bed192a37372 2024-05-19T07:50:09+00:00 Magnetospheric accretion and spin-down of the prototypical classical T Tauri star AA Tau Donati, J. -F. Skelly, M. B. Bouvier, J. Gregory, S. G. Grankin, K. N. Jardine, M. M. Hussain, G. A. J. Ménard, F. Dougados, C. Unruh, Y. Mohanty, S. Aurière, M. Morin, J. Farès, R. 2010-12-21 https://discovery.dundee.ac.uk/en/publications/0193c517-3ab0-4884-90b9-bed192a37372 https://doi.org/10.1111/j.1365-2966.2010.17409.x https://ui.adsabs.harvard.edu/abs/2010MNRAS.409.1347D/abstract eng eng https://discovery.dundee.ac.uk/en/publications/0193c517-3ab0-4884-90b9-bed192a37372 info:eu-repo/semantics/openAccess Donati , J -F , Skelly , M B , Bouvier , J , Gregory , S G , Grankin , K N , Jardine , M M , Hussain , G A J , Ménard , F , Dougados , C , Unruh , Y , Mohanty , S , Aurière , M , Morin , J & Farès , R 2010 , ' Magnetospheric accretion and spin-down of the prototypical classical T Tauri star AA Tau ' , Monthly Notices of the Royal Astronomical Society , vol. 409 , no. 4 , pp. 1347-1361 . https://doi.org/10.1111/j.1365-2966.2010.17409.x techniques: polarimetric stars: formation stars: imaging stars: individual: AA Tau stars: magnetic field stars: rotation /dk/atira/pure/subjectarea/asjc/3100/3103 name=Astronomy and Astrophysics article 2010 ftunivdundeepure https://doi.org/10.1111/j.1365-2966.2010.17409.x 2024-05-01T00:23:38Z From observations collected with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope (CFHT) and with the NARVAL spectropolarimeter at the Télescope Bernard Lyot (TBL), we report the detection of Zeeman signatures on the prototypical classical T Tauri star AA Tau, both in photospheric lines and accretion-powered emission lines. Using time series of unpolarized and circularly polarized spectra, we reconstruct at two epochs maps of the magnetic field, surface brightness and accretion-powered emission of AA Tau. We find that AA Tau hosts a 2-3 kG magnetic dipole tilted at ≃20° to the rotation axis, and of presumably dynamo origin. We also show that the magnetic poles of AA Tau host large cool spots at photospheric level and accretion regions at chromospheric level.The accretion rate at the surface of AA Tau at the time of our observations (estimated from the emission in the He I D 3 line mainly) is strongly variable, ranging from -9.6 to -8.5 and equal to -9.2 in average (in logarithmic scale and in M ☉ yr -1 ); this is an order of magnitude smaller than the disc accretion rate at which the magnetic truncation radius (below which the disc is disrupted by the stellar magnetic field) matches the corotation radius (where the Keplerian period equals the stellar rotation period) - a necessary condition for accretion to occur. It suggests that AA Tau is largely in the propeller regime, with most of the accreting material in the inner disc regions being expelled outwards and only a small fraction accreted towards the surface of the star. The strong variability in the observed surface mass accretion rate and the systematic time-lag of optical occultations (by the warped accretion disc) with respect to magnetic and accretion-powered emission maxima also support this conclusion.Our results imply that AA Tau is being actively spun-down by the star/disc magnetic coupling and appears as an ideal laboratory for studying angular momentum losses of forming suns in the propeller regime. Article in Journal/Newspaper narval narval Discovery - University of Dundee Online Publications Monthly Notices of the Royal Astronomical Society 409 4 1347 1361 |
institution |
Open Polar |
collection |
Discovery - University of Dundee Online Publications |
op_collection_id |
ftunivdundeepure |
language |
English |
topic |
techniques: polarimetric stars: formation stars: imaging stars: individual: AA Tau stars: magnetic field stars: rotation /dk/atira/pure/subjectarea/asjc/3100/3103 name=Astronomy and Astrophysics |
spellingShingle |
techniques: polarimetric stars: formation stars: imaging stars: individual: AA Tau stars: magnetic field stars: rotation /dk/atira/pure/subjectarea/asjc/3100/3103 name=Astronomy and Astrophysics Donati, J. -F. Skelly, M. B. Bouvier, J. Gregory, S. G. Grankin, K. N. Jardine, M. M. Hussain, G. A. J. Ménard, F. Dougados, C. Unruh, Y. Mohanty, S. Aurière, M. Morin, J. Farès, R. Magnetospheric accretion and spin-down of the prototypical classical T Tauri star AA Tau |
topic_facet |
techniques: polarimetric stars: formation stars: imaging stars: individual: AA Tau stars: magnetic field stars: rotation /dk/atira/pure/subjectarea/asjc/3100/3103 name=Astronomy and Astrophysics |
description |
From observations collected with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope (CFHT) and with the NARVAL spectropolarimeter at the Télescope Bernard Lyot (TBL), we report the detection of Zeeman signatures on the prototypical classical T Tauri star AA Tau, both in photospheric lines and accretion-powered emission lines. Using time series of unpolarized and circularly polarized spectra, we reconstruct at two epochs maps of the magnetic field, surface brightness and accretion-powered emission of AA Tau. We find that AA Tau hosts a 2-3 kG magnetic dipole tilted at ≃20° to the rotation axis, and of presumably dynamo origin. We also show that the magnetic poles of AA Tau host large cool spots at photospheric level and accretion regions at chromospheric level.The accretion rate at the surface of AA Tau at the time of our observations (estimated from the emission in the He I D 3 line mainly) is strongly variable, ranging from -9.6 to -8.5 and equal to -9.2 in average (in logarithmic scale and in M ☉ yr -1 ); this is an order of magnitude smaller than the disc accretion rate at which the magnetic truncation radius (below which the disc is disrupted by the stellar magnetic field) matches the corotation radius (where the Keplerian period equals the stellar rotation period) - a necessary condition for accretion to occur. It suggests that AA Tau is largely in the propeller regime, with most of the accreting material in the inner disc regions being expelled outwards and only a small fraction accreted towards the surface of the star. The strong variability in the observed surface mass accretion rate and the systematic time-lag of optical occultations (by the warped accretion disc) with respect to magnetic and accretion-powered emission maxima also support this conclusion.Our results imply that AA Tau is being actively spun-down by the star/disc magnetic coupling and appears as an ideal laboratory for studying angular momentum losses of forming suns in the propeller regime. |
format |
Article in Journal/Newspaper |
author |
Donati, J. -F. Skelly, M. B. Bouvier, J. Gregory, S. G. Grankin, K. N. Jardine, M. M. Hussain, G. A. J. Ménard, F. Dougados, C. Unruh, Y. Mohanty, S. Aurière, M. Morin, J. Farès, R. |
author_facet |
Donati, J. -F. Skelly, M. B. Bouvier, J. Gregory, S. G. Grankin, K. N. Jardine, M. M. Hussain, G. A. J. Ménard, F. Dougados, C. Unruh, Y. Mohanty, S. Aurière, M. Morin, J. Farès, R. |
author_sort |
Donati, J. -F. |
title |
Magnetospheric accretion and spin-down of the prototypical classical T Tauri star AA Tau |
title_short |
Magnetospheric accretion and spin-down of the prototypical classical T Tauri star AA Tau |
title_full |
Magnetospheric accretion and spin-down of the prototypical classical T Tauri star AA Tau |
title_fullStr |
Magnetospheric accretion and spin-down of the prototypical classical T Tauri star AA Tau |
title_full_unstemmed |
Magnetospheric accretion and spin-down of the prototypical classical T Tauri star AA Tau |
title_sort |
magnetospheric accretion and spin-down of the prototypical classical t tauri star aa tau |
publishDate |
2010 |
url |
https://discovery.dundee.ac.uk/en/publications/0193c517-3ab0-4884-90b9-bed192a37372 https://doi.org/10.1111/j.1365-2966.2010.17409.x https://ui.adsabs.harvard.edu/abs/2010MNRAS.409.1347D/abstract |
genre |
narval narval |
genre_facet |
narval narval |
op_source |
Donati , J -F , Skelly , M B , Bouvier , J , Gregory , S G , Grankin , K N , Jardine , M M , Hussain , G A J , Ménard , F , Dougados , C , Unruh , Y , Mohanty , S , Aurière , M , Morin , J & Farès , R 2010 , ' Magnetospheric accretion and spin-down of the prototypical classical T Tauri star AA Tau ' , Monthly Notices of the Royal Astronomical Society , vol. 409 , no. 4 , pp. 1347-1361 . https://doi.org/10.1111/j.1365-2966.2010.17409.x |
op_relation |
https://discovery.dundee.ac.uk/en/publications/0193c517-3ab0-4884-90b9-bed192a37372 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1111/j.1365-2966.2010.17409.x |
container_title |
Monthly Notices of the Royal Astronomical Society |
container_volume |
409 |
container_issue |
4 |
container_start_page |
1347 |
op_container_end_page |
1361 |
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1799468751092973568 |