  We propose a method to distinguish between planetary and stellar companions
to stars which 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 the model which 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 to the star radii. 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, 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 radius less than
1.5 Jupiter radius. The method is not able to distinguish between a planet and
a dwarf star with mass less than 0.1 $M_\odot$, 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 high resolution spectroscopy follow up.
