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Session 8 - Planets and Comets.
Display session, Monday, June 08
Atlas Ballroom,
With Keck I, we are surveying 360 GKM main sequence stars for Doppler periodicities indicative of planetary companions. We present the stellar characteristics of the target list, including Ca II HK emission, ages, and rotation periods. The target list includes only stars older than 2 Gyr to reduce photospheric jitter. The Doppler survey is designed to detect true extrasolar analogs of the giant planets in our Solar System, i.e., Jupiter-mass companions orbiting between 3 - 10 AU. The Keck HIRES spectrometer with an Iodine Cell is currently achieving a Doppler precision of 5 m/s, with improvements yet to be made. The existing precision is just adequate to detect jupiters within 5 AU, which induce reflex velocities of 12.5 m/s X sini. To date we have about 4 Doppler observations of each star, obtained during the past 1.5 yr. Prospective planetary candidates appear already as stars which exhibit velocity variability in excess of the 5 m/s errors by a factor of four. Approximately 5% of the Keck stars exhibit such excess variability, which indicates the occurrence rate of Jupiter-mass companions within 1 AU. Future Keplerian fits to additional Doppler measurements will provide confirmation or rejection of these planetary candidates.
