J/A+A/622/A72 Intermediate-mass T Tau stars spectra (Villebrun+, 2019)
The magnetic fields of intermediate-mass T Tauri stars.
I. Magnetic detections and fundamental stellar parameters.
Villebrun F., Alecian E., Hussain G., Bouvier J., Folsom C.P.,
Lebreton Y., Amard L., Charbonnel C., Gallet F., Haemmerle L.,
Boehm T., Johns-Krull C., Kochukhov O., Marsden S.C., Morin J.,
Petit P.
<Astron. Astrophys. 622, A72 (2019)>
=2019A&A...622A..72V 2019A&A...622A..72V (SIMBAD/NED BibCode)
ADC_Keywords: Stars, pre-main sequence ; Spectroscopy ; Magnetic fields ;
Keywords: stars: activity - stars: fundamental parameters -
stars: magnetic field - stars: pre-main sequence -
stars: variables: T Tauri, Herbig Ae/Be
Abstract:
The origin of the fossil magnetic fields detected in 5 to 10% of
intermediate-mass main sequence stars is still highly debated.
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.
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 vsini) 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 time-scale of the order of few times 0.1Myr.
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.
Description:
Reduced, normalised spectra obtained with the instrument HARPSpol.
HARPSpol is the polarimetric module of the HARPS spectrograph
located at La Silla observatory. Spectra where obtained in 2012.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 78 23 List of studied stars
sp/* . 23 Individual spectra
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- Name Star name
22- 23 I2 h RAh Simbad right ascension (J2000)
25- 26 I2 min RAm Simbad right ascension (J2000)
28- 32 F5.2 s RAs Simbad right ascension (J2000)
34 A1 --- DE- Simbad declination sign (J2000)
35- 36 I2 deg DEd Simbad declination (J2000)
38- 39 I2 arcmin DEm Simbad declination (J2000)
41- 44 F4.1 arcsec DEs Simbad declination (J2000)
46- 78 A33 --- FileName Name of the file with spectrum,
in subdirectory sp
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Byte-by-byte Description of file (#): sp/*
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Bytes Format Units Label Explanations
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1- 10 F10.4 0.1nm lambda Wavelength
12- 23 E12.4 --- I/Ic Normalised intensity
24- 35 E12.4 --- V/Ic Normalised Stokes V parameter
36- 47 E12.4 --- N1/Ic Normalised Stokes N1 parameter
48- 59 E12.4 --- N2/Ic Normalised Stokes N2 parameter
60- 71 E12.4 --- e_I Error on the intensities
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Acknowledgements:
Evelyne Alecian, evelyne.alecian(at)univ-grenoble-alpes.fr
(End) Evelyne Alecian [IPAG, France], Patricia Vannier [CDS] 29-Jan-2019