AAS 196th Meeting, June 2000
Session 41. Globular Clusters
Display, Wednesday, June 7, 2000, 10:00am-7:00pm, Empire Hall South

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[41.07] Blue Stragglers in the Core of 47~Tucanae (NGC~104): Bonus of an HST Planetary Search

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

A secondary data product from the 8.3~d HST campaign to search for planetary transits in 47~Tucanae is a set of coadded F555W (V), F814W (I), and F336W (U) images with WFPC2 of unprecedented depth and resolution (see the poster by R. L. Gilliland, et al.). The pointings cover about 100 sub-pixel dither positions so that it is possible to construct 4\times oversampled images with \rm FWHM\lesssim70~mas and \lesssim140~mas point spread functions in the PC and WF CCDs, respectively. This poster uses this high quality data set to study ~00 blue stragglers in 47~Tuc's core. These include: a bright, strongly centrally concentrated population, and a faint population whose radial distribution is similar to that of the giants. The faint straggler region of the color-magnitude diagram tends to be contaminated by subgiant/turnoff star blend artifacts even in ``normal resolution'' (i.e., non-oversampled) WFPC2 images; this is illustrated using archival short WFPC2 images of 47~Tuc. A statistical technique is used to separate blend artifacts from true faint blue stragglers---the ultra deep WFPC2 data set provides a cross check. The technique should be useful for blue straggler studies of other clusters for which only normal resolution WFPC2 data are available. The luminosity function and photometric properties of these two kinds of 47~Tuc blue stragglers are compared to predictions of blue straggler formation models. Blue stragglers are also discussed in relation to millisecond pulsars and other exotic objects in the cluster core.

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

The author(s) of this abstract have provided an email address for comments about the abstract: raja@ucolick.org

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