Spectral Energy Distribution of Blue Stragglers in the core of 47 Tucanae

Abstract

We have constructed the Spectral Energy Distributions (SEDs) of a sample of Blue Straggler Stars (BSSs) in the core of the globular cluster 47 Tucanae, taking advantage of the large set of high resolution images, ranging from the ultraviolet to the near infrared, obtained with the ACS/HRC camera of the Hubble Space Telescope. Our final BSS sample consists of 22 objects, spanning the whole color and magnitude extension of the BSS sequence in 47 Tucanae. We fitted the BSS broadband SEDs with models to derive temperature, surface gravity, radius, luminosity and mass. We show that BSSs indeed define a mass sequence, where the mass increases for increasing luminosity. Interestingly, the BSS masses estimates from the SED fitting turn out to be comparable to those derived from the projection of the stellar position in the color-magnitude diagram onto standard star evolutionary tracks. We compare our results with previous, direct mass estimates of a few BSSs in 47 Tucanae. We also find a couple of supermassive BSS candidates, i.e., BSSs with a mass larger than twice the turn-off mass, the formation of which must have involved more than two progenitors.

19 pages, 12 figures, 3 tables, accepted for publication in ApJ

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• Discovery of a double sequence of blue straggler stars in the core-collapsed globular cluster NGC 6256
• Empirical measurement of the dynamical ages of three globular clusters and some considerations on the use of the dynamical clock
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• Kinematic complexity around NGC419: resolving the proper motion of the cluster, the Small Magellanic Cloud and the Magellanic Bridge
• Searching for new observational signatures of the dynamical evolution of star clusters
• The dynamical age of the LMC globular cluster NGC 1835 using the "dynamical clock"
• Rotational velocities of Blue Straggler Stars in the Globular Cluster M55
• Detection of a white dwarf orbiting a Carbon-Oxygen depleted blue straggler in 47 Tucanae
• Stellar populations of the globular cluster NGC 5053 investigated using AstroSat-Ultra Violet Imaging Telescope
• Structural parameters, chronological age and dynamical age of the LMC globular cluster NGC 1754
• Study of dynamical status of the globular cluster NGC 1851 using Ultraviolet Imaging Telescope