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Session 70 - Searching for Other Planetary Systems.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center

[70.18] Observations to Detect Planets Around Eclipsing Binary Systems

L. R. Doyle, J. M. Jenkins (SETI Inst.), H. -J. Deeg, E. Martin (I. Astro. Canarias), J. Schneider, M. Chevreton (Obs. Meudon), E. Paleologou, N. Kylafis (U. Crete), W. -B. Lee, H. -I. Kim (Korea Obs.), E. Dunham (NASA Ames), E. Blue (SRI), D. Toublanc (U. Bordeaux)

We present preliminary results from the ongoing ground-based photometric observing program of the TEP (Transit of Extrasolar Planets) network to detect planets in orbit around eclipsing binary stars. Observing eclipsing binaries overcomes the statistical improbability of planetary transits as the planetary orbital plane may be expected to be parallel with the binary orbital plane due to precessionally induced damping (Schneider and Doyle 1995). Observing the smallest such systems assists in overcoming the atmospheric scintillation limits on photometric detection. (We are presently observing the CM Draconis system whose equivalent stellar area is only 12% that of a solar-type star, allowing direct detections of transiting planets an order of magnitude smaller in area than could be detected around solar-type stars.) Significant improvement in the detectability,- well below the rms noise,- is also achieved by cross-correlating the observational light curves with models of all possible planetary transit configurations (a matched-filter signal detection algorithm). In this approach the expected quasi-periodic transit signals are ``co-added" to obtain a high cumulative signal-to-noise ratio (SNR) from the low SNR individual points. As an example, with moderately good photometry (\approx 0.7%) using 0.9-meter ground-based telescopes, this technique should allow the detection of 87% of all \ge 2-Earth-radii planets with periods of 60 days or less at the 99.9% confidence level (i.e. 0.001 chance of a false alarm) within a 6-month observational period (Jenkins et al.1995). On the other hand, giant outer planets may also be photometrically detected without having to await a transit. A small eclipsing binary system will be significantly displaced about a binary / planet barycenter if a giant (i.e. jovian-mass) planet is in orbit around the system. This will cause a slow, periodic drift in the times of eclipse minima (Doyle et al. 1995). We show that occasional timing of eclipse minima to within a couple seconds accuracy (using a standard GPS system) over a few years is sufficient to allow a survey of eclipsing binary systems with ``Jupiters" around them in over 200 such small-mass systems.

Schneider, J. and L.R. Doyle, (1995), ``Ground-Based Detection of Terrestrial Planets By Photometry: The Case for CM Draconis," Planetary and Space Science, in press.

Jenkins, J.M., L.R. Doyle, D.K. Cullers, (1995), ``A Matched Filter Method for Ground-Based Sub-Noise Detection of Terrestrial Extrasolar Planets in Eclipsing Binaries: Application to CM Draconis," Icarus, in press.

Doyle, L.R., E.T. Dunham, H.-J. Deeg, J.E. Blue, and J.M. Jenkins, "Detectability of Terrestrial Extrasolar Planets: U.C. Lick Observations of CM Draconis, J.G.R. Planets, in press.

Program listing for Wednesday