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F. Alston, G. W. Henry, G. S. Burks (Tennessee State University)
Nearly all of the 100 plus extrasolar planets discovered to date have been detected via precise (3--6 m s-1) radial velocity measurements of solar-type stars. The majority of candidate stars surveyed so far were selected to avoid young, active stars because of the associated high levels (10--100 m s-1) of radial velocity jitter in these stars. Persistent starspot activity, lasting for several stellar rotations, can produce periodic radial velocity signals that mimic the presence of orbiting planets. Thus, the extrasolar planetary systems detected so far represent mature systems that have completed most of their planetary orbital evolution. Finding much younger systems and gaining insight into their formation and early evolution requires extending extrasolar planet search surveys to much younger stars, in spite of the radial velocity complications caused by stellar activity.
Precise photometry of planetary candidate stars has proven very useful in interpreting the results of radial velocity observations by helping to distinguish between the effects of true reflex motion caused by planetary companions and the radial velocity effects of starspot activity. Several examples of periodic radial velocity variations caused by surface activity have been found. Therefore, we are conducting a photometric survey of 93 young solar-type stars (ages 3 Myr to 3 Gyr) with our automatic photometric telescopes (APTs) at Fairborn Observatory. These stars were selected from a list of targets to be observed by the SIRTF satellite as part of the Legacy Science Project "The Formation and Evolution of Planetary Systems: Placing Our Solar System in Context". SIRTF will study the evolution of planetary systems around these stars by observing their dust disks. Also, the 10-meter Keck telescope will make precise radial velocity observations of these 93 stars to search for young planetary systems. Our APT observations complement the SIRTF and Keck observations by measuring the level of starspot activity in these stars and, in many cases, determining their rotation periods directly. This information will allow the detection of young planetary systems around these stars to be made with greater confidence. We present preliminary results for several stars, including new rotation periods.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.