The Cluster AgeS Experiment (CASE) – VIII. Age and distance of the Globular Cluster 47 Tuc from the analysis of two detached eclipsing binaries

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DOI	Resolve DOI: https://doi.org/10.1093/mnras/staa032
Author	Search for: Thompson, I. B.; Search for: Udalski, A.; Search for: Dotter, A.; Search for: Rozyczka, M.; Search for: Schwarzenberg-Czerny, A.; Search for: Pych, W.; Search for: Beletsky, Y.; Search for: Burley, G. S.¹; Search for: Marshall, J. L.; Search for: Mcwilliam, A.; Search for: Morrell, N.; Search for: Osip, D.; Search for: Monson, A.; Search for: Persson, S. E.; Search for: Szymański, M. K.; Search for: Soszyński, I.; Search for: Poleski, R.; Search for: Ulaczyk, K.; Search for: Wyrzykowski, Ł.; Search for: Kozłowski, S.; Search for: Mróz, P.; Search for: Pietrukowicz, P.; Search for: Skowron, J.
Affiliation	National Research Council Canada. Herzberg Astronomy and Astrophysics
Format	Text, Article
Subject	binaries: eclipsing; binaries: spectroscopic; globular clusters: individual (47 Tuc); stars: individual (V69 47 Tuc, E32 47 Tuc)
Abstract	We use photometric and spectroscopic observations of the eclipsing binary E32 in the globular cluster 47 Tuc to derive the masses, radii, and luminosities of the component stars. The system has an orbital period of 40.9 d, a markedly eccentric orbit with e = 0.24, and is shown to be a member of or a recent escaper from the cluster. We obtain Mp = 0.862 ± 0.005 M, Rp = 1.183 ± 0.003 R, Lp = 1.65 ± 0.05 L for the primary and Ms = 0.827 ± 0.005 M, Rs = 1.004 ± 0.004 R, Ls = 1.14 ± 0.04 L for the secondary. Based on these data and on an earlier analysis of the binary V69 in 47 Tuc, we measure the distance to the cluster from the distance moduli of the component stars, and, independently, from a colour – surface brightness calibration. We obtain 4.55 ± 0.03 and 4.50 ± 0.07 kpc, respectively – values compatible within 1 σ with recent estimates based on Gaia DR2 parallaxes. By comparing the M–R diagram of the two binaries and the colour–magnitude diagram of 47 Tuc to Dartmouth model isochrones we estimate the age of the cluster to be 12.0 ± 0.5 Gyr, and the helium abundance of the cluster to be Y ≈ 0.25.
Publication date	2020-01-17
Publisher	Oxford University Press
Copyright statement	© 2020 The Royal Astronomical Society
In	Monthly Notices of the Royal Astronomical Society 492, no. 3: 4254–4267.
Note	Erratum published in volume 494, issue 1, pages 846-9, May 2020. DOI: 10.1093/mnras/staa686
Language	English
Peer reviewed	Yes
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Record identifier	a085eda2-37c5-4fd7-9ecb-6f0cd6d71a2a
Record created	2020-06-26
Record modified	2020-06-29

Date modified:: 2025-12-11