J/MNRAS/390/545 Magnetic field and velocity of early M dwarfs (Donati+, 2008)
Large-scale magnetic topologies of early M dwarfs.
Donati J.-F., Morin J., Petit P., Delfosse X., Forveille T., Auriere M.,
Cabanac R., Dintrans B., Fares R., Gastine T., Jardine M.M., Lignieres F.,
Paletou F., Ramirez Velez J.C., Theado S.
<Mon. Not. R. Astron. Soc., 390, 545-560 (2008)>
=2008MNRAS.390..545D 2008MNRAS.390..545D
ADC_Keywords: Stars, M-type ; Magnetic fields
Keywords: techniques: polarimetric - stars: activity - stars: magnetic fields -
stars: low-mass, brown dwarfs - stars: rotation
Abstract:
We present here additional results of a spectropolarimetric survey of
a small sample of stars ranging from spectral type M0 to M8 aimed at
investigating observationally how dynamo processes operate in stars on
both sides of the full convection threshold (spectral type M4).
The present paper focuses on early M stars (M0-M3), that is above
the full convection threshold. Applying tomographic imaging techniques
to time series of rotationally modulated circularly polarized profiles
collected with the NARVAL spectropolarimeter, we determine the
rotation period and reconstruct the large-scale magnetic topologies of
six early M dwarfs. We find that early-M stars preferentially host
large-scale fields with dominantly toroidal and non-axisymmetric
poloidal configurations, along with significant differential rotation
(and long-term variability); only the lowest-mass star of our
subsample is found to host an almost fully poloidal, mainly
axisymmetric large-scale field resembling those found in mid-M dwarfs.
Description:
Spectropolarimetric observations of the selected M dwarfs were
collected with NARVAL and the 2m Telescope Bernard Lyot (TBL), between
2007 January and 2008 February (in three different runs).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 61 6 Fundamental parameters of our sample early-M
dwarf stars
tables.dat 82 138 Dates, magnetic field and radial velocity
(tables 2-7 of the paper)
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See also:
B/cfht : Log of CFHT Exposures (CADC, 1979-)
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
III/198 : Palomar/MSU nearby star spectroscopic survey (Hawley+ 1997)
J/A+A/331/581 : Rotation and activity in field M dwarfs (Delfosse+ 1998)
J/A+A/417/651 : NEXXUS ROSAT survey of coronal X-ray (Schmitt+ 2004)
J/MNRAS/390/567 : Magnetic topologies of mid M dwarfs (Morin+, 2008)
J/MNRAS/407/2269 : Magnetic topologies of late M dwarfs (Morin+, 2010)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Name Designations of the star
7 A1 --- --- [/]
8- 14 A7 --- SName GJ name
16- 19 A4 --- SpT MK spectral type
21- 24 F4.2 solMass Mass Mass of the star (1)
26- 29 F4.1 [10-7W] Lbol Logarithmic bolometric luminosity (2)
31 A1 --- l_LX/Lbol Limit flag on LX/Lbol
32- 35 F4.1 [---] LX/Lbol Ratio of X-ray to bolometric luminosity (3)
37- 38 I2 km/s vsini Equatorial rotational velocity along line of
sight (this paper, accuracy ∼1km/s)
40- 44 F5.2 d Prot Rotation period (this paper)
46- 47 I2 d tauc Convective turnover time (4)
49- 53 F5.3 --- Ro Rossby number (Prot/tauc)
55- 58 F4.2 solRad Rad Theoretical stellar radius (5)
60- 61 I2 deg i Inclination of the stellar rotation axis
(this paper)
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Note (1): Derived from the Hipparcos distance and J, H and K magnitudes using
the mass-luminosity relations of Delfosse et al. (2000A&A...364..217D 2000A&A...364..217D)
except for GJ 182 for which we used the evolutionary models of Baraffe
et al. (1998, Cat. J/A+A/337/403), see text.
Note (2): Derived from the mass and the models of Baraffe et al.
(1998, Cat. J/A+A/337/403).
Note (3): From Kiraga & Stepien (2007AcA....57..149K 2007AcA....57..149K) or from the NEXXUS
data base, Schmitt & Liefke (2004, Cat J/A+A/417/651) or from Wood
et al. (1994ApJS...93..287W 1994ApJS...93..287W) for GJ 49
Note (4): From Kiraga & Stepien (2007AcA....57..149K 2007AcA....57..149K)
Note (5): Predicted by the theoretical models of Baraffe et al.
(1998, Cat. J/A+A/337/403)
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Byte-by-byte Description of file: tables.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Name Designation of the star
8- 17 A10 "YYYY/DD/MM" Obs.date UT date of observation
19- 26 A8 "h:m:s" Obs.time Time of observation (hh:mm:ss)
28- 40 F13.5 d HJD UT heliocentric Julian date of observation
42- 46 A5 --- Texp Exposure time (NxNNN in s)
48- 50 I3 --- S/N Signal to noise ratio (1)
52- 55 F4.1 10-4 sigma rms noise level of V profile (2)
57- 63 F7.3 --- E Rotation cycle (3)
65- 70 F6.1 10-4T Bl Longitudinal magnetic field (Gauss)
72- 75 F4.1 10-4T e_Bl rms uncertainty on Bl
77- 82 F6.2 km/s RV Radial velocity (4)
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Note (1): Peak S/N (per 2.6km/s velocity bin).
Note (2): noise is relative to the unpolarized continuum level and per 1.8km/s
velocity bin of the Least-Square Deconvolution (LSD) Stokes V profile;
it is expressed in 10-4Ic units.
Note (3): E is computed with the ephemeris: HJD=2454100.0+Prot*E. Prot is
taken from table1.
Note (4): absolute accuracy 0.10km/s, internal accuracy 0.03km/s.
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History:
From electronic version of the journal
References:
Morin et al., Paper II 2008MNRAS.390..567M 2008MNRAS.390..567M, Cat. J/MNRAS/390/567
(End) Patricia Vannier [CDS] 29-Jun-2010