A lightcurve of the eclipsing binary CM Draconis has been analyzed for the presence of transits of planets of size >= 2.5 Earth-radii (Re), with periods of 60 days or less, and in co-planar orbits around the binary system. About 400 million model lightcurves, representing transits from planets with periods ranging from 7 to 60 days, have been matched/correlated against these data. This process we call the "transit detection algorithm" or TDA. The resulting `transit-statistics' for each planet candidate allow the quantification of detection probabilities, and of false alarm rates. Our current lightcurve of CM Dra has a coverage of 1014 hours with 26,043 individual points, at a photometric precision between 0.2% and 0.7%. Planets significantly larger then 3Re would constitute a `supra-noise' detection, and for periods of 60 days or less, they would have been detected with a probability of 90%. `Subnoise' detections of smaller planets are more constrained. For example, 2.5 Re planets with 10-day periods or less would have been detected with an 80% probability. The necessity for predicted observations is illustrated with the nine top planet candidates that emerged from our TDA analysis. They are the planet candidates with the highest transit-statistics from the 1994-1998 observing seasons and, for them, transits for the 1999 observing season were predicted. Of the seven candidates that were then observationally tested in 1999, all were ruled out except one, which needs further observational confirmation. We conclude that the photometric 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. (Refer to PDF file for exact formulas).

Publication Date



This is the pre-print of an article published by the American Astronomical Society. The final, published version is available here: https://doi.org/10.1086/308830

© 2000 The American Astronomical Society

Also archived in: arXiv:astro-ph/0001177 v1 11 Jan 2000AND SETI 01/2000

LRD wishes to thank the SETI Institute for a special observing grant, and the University of California, Lick Observatory allocation committee for continued substantial time on the Crossley telescope (incidentally the oldest professional-sized reflecting telescope, first silvered in the late 1870s; see Stone 1979). HJD acknowledges a grant `Formación de Personal Investigador' by the Spanish `Ministerio de Educación y Cultura' for the years 1997 and 1998. The IAC80 and OGS telescopes are operated at Izaña Observatory, Tenerife by the Instituto de Astrofísica de Canarias. Capilla Peak Observatory is operated by the Institute for Astrophysics of the University of New Mexico. (The contributions of the other previously participating observatories for the years 1994 through 1996 are given in TEP1.)

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Department, Program, or Center

School of Physics and Astronomy (COS)


RIT – Main Campus