Search for planetary candidates within the ogle stars.

Abstract

We develop a method to distinguish between planetary and stellar companions to stars that present a periodic decrease in brightness, interpreted as a transit. Light curves from a total of 177 stars from the OGLE project were fitted by a model that simulates planetary transits using an opaque disk in front of an image of the Sun. The simulation results yield the orbital radius in units of stellar radii, the orbital inclination angle, and the ratio of the planet radius to the star radius. Combining Kepler's third law with a mass-radius relation for main-sequence stars, it was possible to estimate values for the masses and radii of both the primary and secondary objects. This model was successfully tested with the confirmed planets orbiting the stars HD 209458, TrES-1, and OGLE-TR 10, 56, 111, 113, and 132. The method consists of selecting as planetary candidates only those objects with primary densities between 0.7 and 2.3 solar densities (F, G, and K stars) and secondaries with radii of less than 1.5 Jovian radii. The method is not able to distinguish between a planet and a dwarf star with a mass less than 0.1 Msolar, such as OGLE-TR 122. We propose a selection of 28 planetary candidates (OGLE-TR 49, 51, 55, 63, 71, 76, 90, 97, 100, 109, 114, 127, 130, 131, 134, 138, 140, 146, 151, 155, 159, 164, 165, 169, 170, 171, 172, and 174) for follow-up high-resolution spectroscopy. (AU)