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  GJ 674b: a 11 Earth mass planet around a low-mass star
  Last update: November 25, 2007

 
 
 
 
 
 
  • The HARPS search for southern extra-solar planets. X. A m sin i = 11 Mearth planet around the nearby spotted M dwarf GJ 674.
    X. Bonfils, M. Mayor, X. Delfosse, T. Forveille, M. Gillon, C. Perrier, S. Udry, F. Bouchy, C. Lovis, F. Pepe, D. Queloz, N. C. Santos and J.-L. Bertaux, 2007
    A&A 474, 293 (ADS)
  • Announced during the "Observing Planetary Systems" ESO Workshop held in Santiago, Chile (March 5-8th 2007)
  • Two periodic radial-velocity signals are detected in HARPS data for GJ 674. The short-period signal (P=4.6938 days) is induced by the presence of a 11 Earth mass planet: GJ 674 b. Bonfils et al. demonstrate that the second signal is induced by the presence of cool spots on the surface of the star. The period of this additional signal corresponds to GJ 674 rotation period. See Bonfils et al. for details.

    •  
    HARPS radial-velocity data obtained for GJ 674.
    Top panel: Short-period RV signal induced by GJ 674 b.
    2nd panel: Longer-period RV signal induced by stellar spots.
    (the spot signal is fitted here with a Keplerian model).
    3rd panel: Residuals to the planet+spot Keplerian fit.
    Bottom panel: Lomb-Scargle periodogram of the residuals.
    Larger image


  • Orbital solution: Planet + Spot (from Bonfils et al. 2007):

    Object
    Period
    (days)
    T0
    (JD - 2 400 000)
    Eccentricity
    V
    (km/s)
    Omega
    (deg)
    K1
    (m/s)
    m2sini
    (M_Earth)
    a
    (AU)
    N
    Residuals
    (m/s)
    GJ 674 b
    4.6938 +/- 0.0007
    53780.085 +/- 0.078
    0.20 +/- 0.02
    -
    143 +/- 6
    8.70 +/- 0.19
    11.09
    0.039
    32
    0.82
    Spot
    34.8467 +/- 0.0324
    53767.13 +/- 0.92
    0.20 +/- 0.05
    -
    113 +/- 9
    5.06 +/- 0.19
    -
    -
    "
    "


  • Stellar properties:

    Parameter
    Value
    Reference
    Sp. Type
    M2.5
    Hawley et al. 1997
    pi (mas)
    220.43 +/- 1.63
    Hipparcos
    d (pc)
    4.54 +/- 0.03
    Hipparcos
    m_v (mag)
    9.382 +/- 0.012
    Turon et al. 1993
    m_k (mag)
    4.855 +/- 0.018
    Cutri et al. 2003
    J-K (mag)
    0.86
    Cutri et al. 2003
    T_eff (K)
    3500-3700
    Bonfils et al. 2007
    M_v (mag)
    11.09 +/- 0.04
    Bonfils et al. 2007
    M_k (mag)
    6.57 +/- 0.04
    Bonfils et al. 2007
    L (L_sol)
    0.016
    Bonfils et al. 2007
    M_1 (M_sol)
    0.35
    Bonfils et al. 2007
    L_X/L_Bol
    0.00005
    Huensch et al. 1999
    P_rot (d)
    ~35
    Bonfils et al. 2007
    Vsini (km/s)
    <1
    Bonfils et al. 2007
    Age (Gyr)
    0.1-1
    Leggett 1992
    [Fe/H]
    -0.28 +/- 0.2
    Bonfils et al. 2007


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    stephane.udry@obs.unige.ch