Circular No. 6423 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science) Phone 617-495-7244/7440/7444 (for emergency use only) CM DRACONIS E. Guinan, G. McCook, and S. Wright, Villanova University, write: "We have made a possible photometric detection of a planetary transit eclipse for the eclipsing-binary star CM Dra --- selected as a planet-search target because its orbital plane is seen almost exactly edge-on (Doyle et al. 1995, BAAS 27, 1382). Photoelectric photometry of CM Dra has been conducted from Mt. Hopkins since 1995 using the Four College Consortium 0.8-m APT. The binary (P = 1.268 days) has been well behaved, showing the expected mutual eclipses of the two stellar components and nearly constant light between the narrow eclipse phases. During a 3.5-hr observation beginning June 1.177 UT, CM Dra was fainter by 0.08 mag in the I band; if we assume that this I decrease is due to a planet transiting one of the two dM5 stars, it would have a diameter of about 0.85 that of Jupiter. From the lower limit to the transit duration, the possible planet would have an orbital period of at least several months. Though this decrease in light may be due to starspot development, photometry the day before and after the dimming event showed the system to be at its usual brightness. Evidence of the existence of a planet around CM Dra is being investigated by searching for small periodic deviations of the eclipse timings; a planet of Jupiter's mass at 1 AU would produce about 17-s periodic shift (observable with accurate photometry) in the arrival times of the eclipses of the stars." (C) Copyright 1996 CBAT 1996 June 20 (6423) Daniel W. E. Green