Rubin Data Preview 1: Extending the View of Unresolved Binary Stars in 47 Tucanae

Abstract

Until now, the study of unresolved main sequence binary stars in globular clusters has been possible almost exclusively in their central regions with deep Hubble Space Telescope (HST) observations. We present the first detection of unresolved main-sequence binary stars in the outer field of 47 Tucanae using Rubin Observatory's Data Preview 1 (DP1). Our analysis exploits deep $i$ vs. $g-i$ colour-magnitude diagrams beyond the cluster's half-light radius, reaching almost to the tidal radius. The high-quality photometry allowed to identify unresolved binaries with mass ratios $q$ larger than 0.7. The derived binary fraction of $f_{\mathrm{bin}}(q>0.7)=0.016\pm 0.005$ stands in contrast to the significantly lower values in the cluster innermost regions, as measured from HST photometry. This result provides new empirical input for testing physical processes that drive the formation and evolution of binary stars in globular clusters. It also demonstrates Rubin's unique wide-field and high-precision photometric capabilities to address a broader range of outstanding questions in star cluster research. Future full data releases will enable to significantly expand the study of dense stellar systems across the Milky Way.

5 pages, 2 figures, accepted for publication in PASA Letters

References in corpus (14)

• Gaia EDR3 view on Galactic globular clusters
• The fraction of binary systems in the core of thirteen low-density Galactic globular clusters
• The radial distribution of blue straggler stars and the nature of their progenitors
• The core binary fractions of star clusters from realistic simulations
• Intermediate Mass Black Hole Induced Quenching of Mass Segregation in Star Clusters
• Photometric binaries, mass functions, and structural parameters of 78 Galactic open clusters
• The multiplicity fraction in 202 open clusters from Gaia
• Differential reddening in the direction of 56 Galactic globular clusters
• Rubin Observatory LSST Stars Milky Way and Local Volume Star Clusters Roadmap
• The Vera C. Rubin Observatory Data Preview 1
• Photometric Binaries in 14 Magellanic Cloud Star Clusters
• Binary properties of the globular cluster 47 Tuc (NGC 104). A dearth of short-period binaries
• Hubble Space Telescope survey of Magellanic Cloud star clusters. Binaries among the split main sequences of NGC 1818, NGC 1850, and NGC 2164
• Exploring the formation environment of multiple stellar populations in Globular Clusters through binary systems