A planet-sized transiting star around OGLE-TR-122

F. Pont, C. H. F. Melo, F. Bouchy, S. Udry, D. Queloz, M. Mayor, N. C. Santos
2005 Astronomy and Astrophysics  
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
more » ... e 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.
doi:10.1051/0004-6361:200500025 fatcat:qzg2b4af7ngkzlsczj46i6vw2m