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Session 26 - Stars in the Visible & IR.
Display session, Tuesday, June 10
South Main Hall,

[26.09] Eclipsing Binaries as Astrophysical Laboratories: Evidence of a Jupiter-size Planet Orbiting the Short Period Eclipsing Binary CM Draconis

E. F. Guinan, G. P. McCook, S. R. Wright (Villanova U.), D. H. Bradstreet (Eastern Coll.)

We report further on the possible photometric detection of a planetary transit eclipse for the dM4.5+dM4.5 (P=1.268d) eclipsing binary star CM Dra. CM Dra was selected as a target for a planetary transit search because its orbital plane is seen almost exactly edge-on and its component stars radii are small. A planet orbiting the binary in the plane of its orbit would transit across the disks of the stars, producing a decrease in brightness proportional to the relative areas of the planet to the stars.

Photoelectric photometry of CM Dra has been conducted from Arizona from 1995-1997 using the Four College Consortium 0.8m Automatic Photometric Telescope (APT). As reported in AC No.6423, during a 3.h interval on 01 June 1996 UT, CM Dra was fainter by 0.08 mag in the I-band. In this paper we present the modelling results of the observed light decrease assuming a planetary transit eclipse of the limb-darkened (x=0.45) dM4.5 stars. Good fits of the light loss were obtained for a planet with a diameter = 0.94 +/-0.04Dj and having an orbital period of P = 2.2 +/-0.4 yrs. This estimated orbital period is close to the elapsed time interval of 2.01 yrs between the transit event reported here and that reported by Martin and Deeg (IAUC No. 6425). Upper limits of the mass of this possible planet of Mp < 5Mj were made by searching for systematic variations of the eclipse arrival times of the eclipsing binary that would occur from the presence of a massive planet or brown dwarf. Observations of additional photometric transits are needed to confirm the presence of a planet in the CM Dra system.This research is supported by NSF grants AST-9315365 to Villanova University and AST-9528506 Four College Consortium. We gratefully acknowedge this support.

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