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J/MNRAS/390/567  Magnetic field and velocity of mid M dwarfs  (Morin+, 2008)
Large-scale magnetic topologies of mid M dwarfs.
    Morin J., Donati J.-F., Petit P., Delfosse X., Forveille T., Albert L.,
    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, 567-581 (2008)>
   =2008MNRAS.390..567M
ADC_Keywords: Stars, M-type ; Magnetic fields

Keywords: stars: magnetic field - stars: low-mass, brown dwarfs -
          stars: rotation - techniques: spectroscopy - techniques: polarimetry

Abstract:
    We present in this paper, the first results of a spectropolarimetric
    analysis of a small sample (∼20) of active stars ranging from spectral
    type M0 to M8, which are either fully convective or possess a very
    small radiative core. This study aims at providing new constraints on
    dynamo processes in fully convective stars. This paper focuses on ve
    stars of spectral type ∼M4, i.e. with masses close to the full
    convection threshold (0.35M☉), and with short rotational periods.
    Tomographic imaging techniques allow us to reconstruct the surface
    magnetic topologies from the rotationally modulated time-series of
    circularly polarized profiles. We find that all stars host mainly
    axisymmetric large-scale poloidal fields. Three stars were observed at
    two different epochs separated by 1yr; we find the magnetic topologies
    to be globally stable on this time-scale. We also provide an accurate
    estimation of the rotational period of all stars, thus allowing us to
    start studying how rotation impacts the large-scale magnetic field.

Description:
    We have collected 107 pairs of Stokes I (unpolarised) and V
    (circularly polarised) spectra with the twin instruments ESPaDOnS at
    CFHT (2003ASPC..307...41D) and NARVAL at TBL between January 2006 and
    February 2008. All spectra were reduced using the Libre-Esprit
    pipeline, and the mean I and V line profiles were extracted using the
    Least-Squares Deconvolution (LSD) technique (1997MNRAS.291..658D). The
    star V374 Peg (2008MNRAS.384...77M) is also included in the discussion
    and in table1.dat.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table1.dat       132        6   Fundamental parameters
tables.dat        90      105   Dates, magnetic field and radial velocity
                              (tables 2-6 of the paper)


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/390/545  : Magnetic topologies of early M dwarfs (Donati+ 2008)
 J/MNRAS/407/2269 : Magnetic topologies of late M dwarfs (Morin+, 2010)


Byte-by-byte Description of file: table1.dat

   Bytes Format Units     Label   Explanations

   1-  8  A8    ---       Name    Designations of the star
  10- 16  A7    ---       SName   GJ name
  18- 19  I2    h         RAh     Simbad Hour of Right Ascension (J2000.0)
  21- 22  I2    min       RAm     Simbad Minute of Right Ascension (J2000.0)
  24- 28  F5.2  s         RAs     Simbad Second of Right Ascension (J2000.0)
      30  A1    ---       DE-     Simbad Sign of the Declination (J2000.0)
  31- 32  I2    deg       DEd     Simbad Degree of Declination (J2000.0)
  34- 35  I2    arcmin    DEm     Simbad Arcminute of Declination (J2000.0)
  37- 40  F4.1  arcsec    DEs     Simbad Arcsecond of Declination (J2000.0)
      42  I1    ---       Tab     ? Number of the corresponding table with
                                    observations in the paper
  44- 47  A4    ---       SpT     MK spectral type (1)
  49- 52  F4.2  solMass   Mass    Mass of the star (2)
      54  A1    ---       l_Mass  Limit flag on e_Mass (2)
  55- 58  F4.2  solMass   e_Mass  Formal 1-σ error bar on Mass (2)
  60- 64  F5.2  [10-7W]   Lbol    Logarithmic bolometric luminosity (3)
  66- 70  F5.2  [---]    LX/Lbol  Ratio of X-ray to bolometric luminosity (4)
  72- 75  F4.1  km/s      vsini   Equatorial rotational velocity along line of
                                   sight (5)
      76  A1    ---      r_vsini  [a] a: vsini from Reiners & Basri, 
                                          2007ApJ...656.1121R
      78  A1    ---       l_Bf    Limit flag on Bf (6)
  79- 81  F3.1  0.1T      Bf      ? Magnetic flux (6)
      82  A1    ---       r_Bf    [a] a: Bf from Reiners & Basri, 
                                          2007ApJ...656.1121R
  84- 91  F8.6  d         Prot    Rotation period (7)
  93-100  F8.6  d         e_Prot  3-σ error bar on Prot (7)
 102-103  I2    d         tauc    Empirical convective turnover time (8)
 105-107  F3.1  ---       Ro      Empirical Rossby number (8)
 109-112  F4.2  solRad    Rsini   ?Stellar radius times sini (9)
     114  A1    ---      l_Rsini  Limit flag on error on Rsini (9)
 115-118  F4.2  solRad   e_Rsini  Formal 1-σ error bar on Rsini (9)
 120-123  F4.2  solRad    Rad     Theoretical stellar radius (10)
     125  A1    ---       l_Rad   Limit flag on error on Rad (10)
 126-129  F4.2  solRad    e_Rad   Formal 1-σ error bar on Rad (10)
 131-132  I2    deg       i       Inclination of the stellar rotation axis (11)

Note (1): SpType is from Reid et al., (1995, Cat. III/198).

Note (2): Absolute J-Band magnitudes are computed from Hipparcos parallaxes
     (I/239) and 2MASS (II/246) apparent magnitudes. Stellar masses are
     then derived using the Delfosse et al. (2000A&A...364..217D)
     mass-luminosity relation. Uncertainties on parallax and mass are
     propagated and mentioned in e_Mass (with a 0.01M_☉ lower limit).
Note (3): Bolometric luminosities suited to Mass are computed from NextGen
     models by Baraffe et al. 1998 (1998A&A...337..403B).
Note (4): X-ray luminosities LX are taken from Schmitt et al.(2004, Cat.
     J/A+A/417/651) and averaged, excluding outliers supposedly due to flares.
Note (5): Most vsini values are taken from studies of FeH molecular bands
     (see refs.dat). For GJ 51 we derive vsini from our spectra. Typical
     uncertainty is of the order of 1km/s, see references.
Note (6): Unsigned magnetic fluxes are taken from studies of FeH molecular
     bands (see refs.dat) whenever available. Typical uncertainties are in
     the 0.05-0.1T range (i.e. 0.5-1kG in CGS units), see references.
Note (7): Rotation periods are derived from Zeeman-Doppler Imaging analysis
     of time-series of LSD circularly polarised spectra. Prot and e_Prot
     are derived by fitting a paraboloid to the chi2 surface as in Petit
     et al. (2002MNRAS.334..374P).
Note (8): Empirical convective turnover times suited to the stellar mass
     are derived using the rotation-X-ray luminosity relation from Kiraga &
     Stepien (2007AcA....57..149K). The Rossby number is then Ro=Prot/tauc.
Note (9): Rsini[solRad]=Prot[d]*vsini[km/s]/50.6145. Error bars are
     propagated and mentioned in e_Rsini (with a 0.01R☉ lower limit).
Note (10): Radii suited to Mass are computed from NextGen models by Baraffe
     et al. (1998A&A...337..403B). Error bar on Mass is propagated (with a
     0.01R☉ lower limit).
Note (11): Rough estimate of the inclination used for Zeeman-Doppler
     imaging, derived by comparing Rad and Rsini.


Byte-by-byte Description of file: tables.dat

   Bytes Format Units      Label     Explanations

   1-  8  A8    ---        Name      Designation of the star
  10- 19  A10 "YYYY/DD/MM" Obs.date  UT date of observation
  21- 28  A8    "h:m:s"    Obs.time  Time of observation (hh:mm:ss)
  30- 42  F13.5 d          HJD       UT heliocentric Julian date of observation
  44- 47  A4    ---        Site      Observation site (CFHT or TBL = Telescope
                                       Bernard Lyot)
  49- 56  A8    s          Texp      Exposure time (NxNNNN.N in s)
  58- 60  I3    ---        S/N       Signal to noise ratio
  62- 64  F3.1  10-4       sigma     rms noise level in polarisation profile (4)
  66- 71  F6.1  10-4T      Bl        Longitudinal magnetic field (Gauss) (1)
  73- 76  F4.1  10-4T      e_Bl      rms uncertainty on Bl (1)
  78- 84  F7.3  ---        E         Rotation cycle (3)
  86- 90  F5.2  km/s       RV        Radial velocity (2)

Note (1): Bl is measured from the LSD Stokes I and V line profiles.

Note (2): The absolute RV accuracy of ESPaDOnS data calibrated with the
     Libre-Esprit pipeline is estimated to be of the order of 100m/s. The
     internal accuracy within a time-series is estimated to be of the order
     of 30m/s.
Note (3): E is computed with the ephemeris: HJD=HJD0+Prot*E. Prot is
     taken from table1 except for VB 10, in this case Prot=0.69d.
Note (4): noise level in the circular polarisation profile produced by
     the Least-Square Deconvolution (LSD) algorithm. It is expressed in
     10-4Ic units, if Ic is the unpolarised continuum level


Acknowledgements:
    Julien Morin, jmorin(at)cp.dias.ie

References:
    Donati et al., Paper I      2008MNRAS.390..545D, J/MNRAS/390/545
(End)                                      Patricia Vannier [CDS]    24-Jun-2010