Magnetic fields of intermediate-mass T Tauri stars I. Magnetic detections and fundamental stellar parameters

Villebrun, F. and Alecian, E. and Hussain, G. and Bouvier, J. and Folsom, C. P. and Lebreton, Y. and Amard, L. and Charbonnel, C. and Gallet, F. and Haemmerle, L. and Bohm, T. and Johns-Krull, C. and Kochukhov, O. and Marsden, S. C. and Morin, J. and Petit, P. (2019) Magnetic fields of intermediate-mass T Tauri stars I. Magnetic detections and fundamental stellar parameters. Astronomy & Astrophysics, 622. pp. 1-21.

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Abstract

Context. The origin of the fossil magnetic fields detected in 5 to 10% of intermediate-mass main sequence stars is still highly debated.
Aims: We want to bring observational constraints to a large population of intermediate-mass pre-main sequence (PMS) stars in order to test the theory that convective-dynamo fields generated during the PMS phases of stellar evolution can occasionally relax into fossil fields on the main sequence.
Methods: Using distance estimations, photometric measurements, and spectropolarimetric data from HARPSpol and ESPaDOnS of 38 intermediate-mass PMS stars, we determined fundamental stellar parameters (Teff, L and v sin i) and measured surface magnetic field characteristics (including detection limits for non-detections, and longitudinal fields and basic topologies for positive detections). Using PMS evolutionary models, we determined the mass, radius, and internal structure of these stars. We compared different PMS models to check that our determinations were not model-dependant. We then compared the magnetic characteristics of our sample accounting for their stellar parameters and internal structures.
Results: We detect magnetic fields in about half of our sample. About 90% of the magnetic stars have outer convective envelopes larger than ̃25% of the stellar radii, and heavier than ̃2% of the stellar mass. Going to higher mass, we find that the magnetic incidence in intermediate-mass stars drops very quickly, within a timescale on the order of few times 0.1 Myr. Finally, we propose that intermediate-mass T Tauri stars with large convective envelopes, close to the fully convective limit, have complex fields and that their dipole component strengths may decrease as the sizes of their convective envelopes decrease, similar to lower-mass T Tauri stars.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Reproduced with permission from Astronomy & Astrophysics, © ESO.
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Sciences (6 Sept 2019 -)
Date Deposited: 23 Jan 2020 03:42
Last Modified: 29 Jan 2020 05:44
Uncontrolled Keywords: stars: activity; stars: fundamental parameters; stars: magnetic field; stars: pre-main sequence; stars: variables: T Tauri; Herbig Ae/Be
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: 10.1051/0004-6361/201833545
URI: http://eprints.usq.edu.au/id/eprint/37369

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