Observational limits on terrestrial-sized inner planets around the CM Draconis system using the photometric transit method with a matched-filter algorithm

A light curve of the eclipsing binary CM Draconis has been analyzed for the presence of transits of planets of size greater than or equal to 2.5 Earth radii (R-E), with periods of 60 days or less, and in coplanar orbits aroun d the binary system. About 400 million model light curves, representing tra nsits from planets with periods ranging from 7 to 60 days, have been matche d/correlated against these data. This process we call the "transit detectio n algorithm" or TDA. The resulting "transit statistics" for each planet can didate allow the quantification of detection probabilities, and of false-al arm rates. Our current light curve of CM Dra has a coverage of 1014 hr with 26,043 ind ividual points, at a photometric precision between 0.2% and 0.7%. Planets s ignificantly larger than 3R(E) would constitute a "supranoise" detection, a nd for periods of 60 days or less, they would have been detected with a pro bability greater than 90%. "Subnoise" detections of smaller planets are mor e constrained. For example, 2.5R(E) planets with 10 day periods or less wou ld have been detected with an 80% probability. The necessity for predicted observations is illustrated with the nine top planet candidates that emerge d from our TDA analysis. They are the planet candidates with the highest tr ansit statistics from the 1994-1998 observing seasons, and for them transit s for the 1999 observing season were predicted. Of the seven candidates tha t were then observationally tested in 1999, all were ruled out except one, which needs further observational confirmation. We conclude that the photom etric transit method is a viable way to search for relatively small, inner extrasolar planets with moderate-sized telescopes using CCD photometry with a matching-filter analysis.