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A planet-sized transiting star around OGLE-TR-122 - Accurate mass and radius near the Hydrogen-burning limit

F. Pont·C. H. F. Melo·F. Bouchy·S. Udry·D. Queloz·M. Mayor·N. C. Santos
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Abstract

We report the discovery and characterisation of OGLE-TR-122b, the smallest main-sequence star to date with a direct radius determination. OGLE-TR-122b transits around its solar-type primary every 7.3-days. With M=0.092+-0.009 Mo and R=0.120 +0.024-0.013 Ro, it is by far the smallest known eclipsing M-dwarf. The derived mass and radius for OGLE-TR-122b are in agreement with the theoretical expectations. OGLE-TR-122b is the first observational evidence that stars can indeed have radii comparable or even smaller than giant planets. In such cases, the photometric signal is exactly that of a transiting planet and the true nature of the companion can only be determined with high-resolution spectroscopy.

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F. Pont, C. H. F. Melo, F. Bouchy, S. Udry, D. Queloz, M. Mayor, N. C. Santos. 2005-03-02. A planet-sized transiting star around OGLE-TR-122 - Accurate mass and radius near the Hydrogen-burning limit. https://doi.org/10.1051/0004-6361%3A200500025

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