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A. Gillman (Tennessee State University), S. M. Henry (Trevecca Nazarene University), G. W. Henry (Tennessee State University)
Tennessee State University operates several automatic photometric telescopes (APTs) at Fairborn Observatory in southern Arizona. Four 0.8 m APTs have been dedicated to measuring subtle luminosity variations that accompany magnetic cycles in solar-type stars. Approximately 1200 program and comparison stars have been observed every clear night in this program for up to 12 years with a precision of approximately 0.0015 mag for a single observation. We have developed a transit-search algorithm, based on fitting a computed transit template for each trial period, and are using it to search our photometric database for transits of unknown companions. Extensive simulations with the APT data have shown that we can reliably recover transits with periods under 10 days as long as the transits have a depth of 0.0030 mag or more, i.e., twice the level of precision of the observations. Thus, due to our high photometric precision, we are sensitive to transits of possible short-period Neptune-mass planets that likely would have escaped detection by current radial velocity techniques. The detection of two unknown grazing eclipsing binaries among our comparison stars, with eclipse depths of only a few millimags, illustrates the capabilities of our program. We will report on the progress of our search and use the results to discuss the frequency of Neptune-mass planets in close orbits around solar-type stars.
This work has been supported by NASA grant NCC5-511 and NSF grant HRD-9706268.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.