Radius and mass of a transiting M dwarf near the hydrogen-burning limit OGLE-TR-123 - Archive ouverte HAL
Article Dans Une Revue Astronomy & Astrophysics - A&A Année : 2006

Radius and mass of a transiting M dwarf near the hydrogen-burning limit OGLE-TR-123

F. Pont
  • Fonction : Auteur
C. Moutou
R. Behrend
  • Fonction : Auteur
M. Mayor
  • Fonction : Auteur
S. Udry
D. Queloz
  • Fonction : Auteur
N. Santos
  • Fonction : Auteur
C. Melo
  • Fonction : Auteur

Résumé

The system OGLE-TR-123, detected by the OGLE planetary transit survey in Carina, was shown by subsequent spectroscopic follow-up to be an eclipsing binary with a very low mass companion ( ). Neither the light curve nor the radial velocity data were sufficient to constrain the parameters more precisely and to exclude alternative explanations in terms of a triple system. In this paper, new HARPS radial velocity data and a precise photometric monitoring of the transit with VLT/FORS2 are presented, resulting in an improved mass and radius determination for OGLE-TR-123b and the rejection of alternative scenarios. We find and for the transiting companion, confirming its nature as a small M dwarf near the hydrogen-burning limit. Its mass-radius relation corresponds to expectations for a relatively young object. The primary is an F dwarf that does not rotate synchronously with the orbital motion. Asynchronous rotation is unexpected in such a close binary (P=1.8 days) but could be explained by the small mass of the secondary, the young age for the system, and the absence of convective envelope in the primary. OGLE-TR-123b is one of only two known objects below 0.1 with directly determined radii, after a similar object was characterised around OGLE-TR-122. The characterisation of OGLE-TR-123 provides another example of the type of system that can closely mimic planetary transits and contaminate transit surveys.
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hal-00019597 , version 1 (03-09-2024)

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F. Pont, C. Moutou, F. Bouchy, R. Behrend, M. Mayor, et al.. Radius and mass of a transiting M dwarf near the hydrogen-burning limit OGLE-TR-123. Astronomy & Astrophysics - A&A, 2006, 447, pp.1035. ⟨10.1051/0004-6361:20053692⟩. ⟨hal-00019597⟩
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