AAS 196th Meeting, June 2000
Session 2. Searching for and Characterizing Extra Solar Planets
Display, Monday, June 5, 2000, 9:20am-6:30pm, Empire Hall South

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[2.03] HST Photometry of 47 Tucanae: Time Series Analysis and Search for Giant Planets

T. M. Brown (NCAR), D. Charbonneau (NCAR,CfA), R.L. Gilliland, M.D. Albrow (STScI), A.S. Burrows (UA), W.D. Cochran, N. Baliber (U Texas), P.D. Edmonds (SAO), S. Frandsen, H. Bruntt (U. Aarhus), P. Guhathakurta, P. Choi, J.H. Howell, D.N.C. Lin, S.S. Vogt (UCSC), G.W. Marcy (UCB), M. Mayor, D. Naef (Obs. Geneve), E.F. Milone, C.R. Stagg, M.D. Williams (U. Calgary), A. Sarajedini (Wesleyan U.), S. Sigurdsson (PSU), D.A. VandenBerg (U. Victoria)

We have analyzed HST time series data of more than 34000 stars in the globular cluster 47 Tuc in a search for transiting Jupiter-sized planets in small orbits. The data consist of roughly 645 time samples each in bands centered at 555 nm and 814 nm, with fairly uniform sampling (except for orbital gaps) over an 8.3-day interval. They are described in detail in a poster by Gilliland et al. We used a matched-filter technique to search for periodic transit events in these time series over a period range between 0.5 and 8.3 days. Blind tests with injected artificial transits yielded recovery rates of about 85% for planets of 1.3 Jupiter radii, and above 60% for planets of 1.0 Jupiter radii, in a sample spanning 4 magnitudes below main sequence turnoff.

At abstract time, analysis was complete for 27000 stars. These data reveal no convincing planet candidates; 15 to 20 detections would be expected if the occurrence rate in 47 Tuc were the same as indicated by radial velocity searches of stars in the solar neighborhood, and if planet radii are indeed above 1 RJup. This discrepancy suggests that at least one of the processes of formation, migration, or survival of close-in planets may be significantly altered in the cluster environment. Many elipsing binaries and other variables were found in this analysis. Some of them are described by Milone et al. in an accompanying poster.

Funding has been provided via a NASA/STScI GO grant.

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