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W. J. Borucki, D. A. Caldwell, D. G. Koch, N. M. Stout-Batalha (NASA Ames Research Center), J. M. Jenkins (SETI Institute), R. L. Showen (Raytheon Corp.)
Doppler velocity searches for extrasolar planets have discovered over fifty planets orbiting solar-like stars. Combining the size determined from transit detections with the mass determined from Doppler velocity measurements yields the density of the extrasolar planet. With the orbital period and characteristics of the central star, these quantities provide a critical test of current theories of planetary structure. Observations of the planet orbiting HD209458 give an estimate of 0.3 g/cc, in agreement with theories of a planet that either formed near the central star or migrated there very shortly after formation. Several transit searches to discover extrasolar planets and determine their sizes are underway.
Our Vulcan photometer at Lick Observatory has a 10-cm aperture, a 49-sq. degree FOV, and has monitored three different star fields for several weeks each for two years. Over 10,000 stars brighter than 12th magnitude have been observed with a precision adequate to detect Jovian-size planets. Hundreds of eclipsing binaries have been found. Over a dozen binaries showing transits with amplitudes as small as those expected for planetary companions demonstrate that the precision attained by the measurements is sufficient. Identification of these companions as grazing binaries or high area-ratio binaries has been accomplished. (See the meeting paper by Posson-Brown et al.) Early estimates of the frequency of planets with orbital periods less than a week ranged from 2 1 geometrical probability near 10 after including missed transits and the fraction of stars that are binaries with short periods or giants, discovery of a few planetary companions are expected. Currently we are investigating several candidates that show low amplitude transits.
This project is funded by the NASA Origins and Astrobiology programs.
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