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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[2.02] An HST Search for Planets in the Globular Cluster 47 Tucanae

R. L. Gilliland, M.D. Albrow (STScI), T.M. Brown (NCAR), D. Charbonneau (NCAR,CfA), A. 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)

HST was used for 8.3 days in July '99 to monitor over 30,000 stars on the main sequence of 47 Tuc photometrically with a goal of detecting planets via transit signals. Expected transit depths for 1.3 Jupiter radii planets increase from 1% near main sequence turnoff to 6% at 4 magnitudes fainter due to decreasing stellar radii. Over this domain realized time series rms, obtained with PSF fitting in difference images, smoothly increases from 0.3% to 2.5%. With ~645 data points in each of WFPC2 F555W and F814W filters any planet with P < 4.2 days should provide securely detectable transits lasting 2-4 hours twice in each of V and I. Based on the frequency of inner-orbit, gas-giant planets from solar neighborhood radial velocity surveys we expect to detect 15 to 20 candidate planets, but see none (with 75% search completion) in this low metalicity, crowded stellar system; see also T.M. Brown poster. Many eclipsing binaries and variable stars are detected; see also E.F. Milone poster.

We provide a project overview and details on: (1) reduction steps and resulting deep (> 100,000s in V, I; 14,360s U) co-added, over-sampled images, (2) key analysis steps that provide near-Poisson limited photometric time-series precisions for dithered, under-sampled, crowded-field images with significant focus variations in time, (3) global summaries of time series precisions and sensitivity to detecting planets, and (4) a few time series of particular interest.

Funding has been provided via a NASA/STScI grant for GO-8267.

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