Observational Limits on Terrestrial‐sized Inner Planets around the CM Draconis System Using the Photometric Transit Method with a Matched‐Filter Algorithm

Abstract

A light curve of the eclipsing binary CM Draconis has been analyzed for the presence of transits of planets of size º2.5 Earth radii with periods of 60 days or less, and in coplanar orbits around the (R E ), binary system. About 400 million model light curves, 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 ÏÏ or TDA. The resulting "" transit statistics ÏÏ for each planet candidate allow the quantiÐcation of detection probabilities, and of false-alarm rates.Our current light curve of CM Dra has a coverage of 1014 hr with 26,043 individual points, at a photometric precision between 0.2% and 0.7%. Planets signiÐcantly larger than would constitute a 3R E "" supranoise ÏÏ detection, and for periods of 60 days or less, they would have been detected with a probability greater than 90%. "" Subnoise ÏÏ detections of smaller planets are more constrained. For example, planets with 10 day periods or less would have been detected with an 80% probability. The neces-2.5R E sity 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 1994È1998 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 conÐrmation. 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-Ðlter analysis.

Photometric Transits from the MACHO Project Database

“…In this analysis the best detection method was found to be the modified matched filter approach of Doyle et al (2000). Revised work by Tingey (2003b) found that a modified version of the boxfitting least-squares method of Kovács et al (2002) gave better results.…”

Improvements to existing transit detection algorithms and their comparison

“…It is therefore not necessary to test the Bayesian. Moreover, the matched filter clearly performed better than the correlation and Deeg's approach (Doyle et al 2000), so the latter two can also be left out. Therefore, only the essential approaches will be included: the matched filter, which was determined to be the best in Paper I and the BLS, which was not implemented in the ideal fashion.…”

Comparative blind test of five planetary transit detection algorithms on realistic synthetic light curves

“…Several transit detection algorithms were proposed in the recent literature: Bayesian algorithms (Doyle et al 2000;Defaÿ et al 2001;Aigrain & Favata 2002), matched filters (Jenkins et al 1996), box-shaped transit finder (Aigrain & Irwin 2004), and the Box-fitting Least Squares (BLS) method (Kovács et al 2002). A theoretical comparison of these methods was proposed (Tingley 2003), which concluded that "no detector is clearly superior for all transit signal energies", but an optimized BLS algorithm still performs slightly better for shallower transits.…”