AAS 205th Meeting, 9-13 January 2005
Session 159 Novae, CVs, Blue Stragglers, and GRB Cosmography
Oral, Thursday, January 13, 2005, 10:00-11:30am, Royal Palm 4-6

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[159.05] Blue Straggler Stars in 4 Globular Clusters: Masses, Rotation Rates and Disks

O. De Marco, D. Zurek, J.A. Ouellette (American Museum of Natural History), T. Lanz (Goddard Space Flight Center/University of Maryland), M.M. Shara (American Museum of Natural History), R.A. Saffer, J.F. Sepinsky (Villanova University)

We present an analysis of optical HST/STIS and HST/FOS spectroscopy of blue stragglers found in the globular clusters 47Tuc, M3, NGC6752 and NGC6397. Spectroscopic masses, and rotation rates are presented which impose constraints on their evolutionary history. 6 blue stragglers in our sample cannot be fit with state of the art non-LTE stellar atmosphere models. The 6 misfits possess Balmer jumps which are too large for the effective temperatures implied by their Paschen continua. We find that our data for these stars are consistent with models only if we account for extra absorption of stellar Balmer photons by an ionized circumstellar disk. Column densities of HI and CaII are derived as are the the disks' thicknesses. This is the first time that a circumstellar disk is detected around blue stragglers. The presence of magnetically-locked disks attached to the stars has been suggested as a mechanism to lose the large angular momentum imparted by the collision event at the birth of these stars. The disks implied by our study might not be massive enough to constitute such an angular momentum sink, but they could be the leftovers of once larger disks.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.