THE CLUSTER AGES EXPERIMENT (CASE). IV. ANALYSIS OF THE ECLIPSING BINARY V69 IN THE GLOBULAR CLUSTER 47 Tuc

Journal Article · Mon Feb 15 00:00:00 EST 2010 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/139/2/329; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21301430

Thompson, I B; Burley, G S ^[1]; Kaluzny, J; Pych, W ^[2]; Rucinski, S M ^[3]; Krzeminski, W ^[4]

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1. Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101-1292 (United States)
2. Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland)
3. David Dunlap Observatory, Department of Astronomy and Astrophysics, University of Toronto, P.O. Box 360, Richmond Hill, ON L4C 4Y6 (Canada)
4. Las Campanas Observatory, Casilla 601, La Serena (Chile)

We use photometric and spectroscopic observations of the eclipsing binary V69-47 Tuc to derive the masses, radii, and luminosities of the component stars. Based on measured systemic velocity, distance, and proper motion, the system is a member of the globular cluster 47 Tuc. The system has an orbital period of 29.5d and the orbit is slightly eccentric with e = 0.056. We obtain M{sub p} = 0.8762 {+-} 0.0048 M {sub sun}, R{sub p} = 1.3148 {+-} 0.0051 R {sub sun}, L{sub p} = 1.94 {+-} 0.21 L {sub sun} for the primary and M{sub s} = 0.8588 {+-} 0.0060 M {sub sun}, R{sub s} = 1.1616 {+-} 0.0062 R {sub sun}, L{sub s} = 1.53 {+-} 0.17 L {sub sun} for the secondary. These components of V69 are the first Population II stars with masses and radii derived directly and with an accuracy of better than 1%. We measure an apparent distance modulus of (m - M) {sub V} = 13.35 {+-} 0.08 to V69. We compare the absolute parameters of V69 with five sets of stellar evolution models and estimate the age of V69 using mass-luminosity-age, mass-radius-age, and turnoff mass-age relations. The masses, radii, and luminosities of the component stars are determined well enough that the measurement of ages is dominated by systematic differences between the evolutionary models, in particular, the adopted helium abundance. By comparing the observations to Dartmouth model isochrones we estimate the age of V69 to be 11.25 {+-} 0.21(random) {+-} 0.85(systematic) Gyr assuming [Fe/H] = -0.70, [{alpha}/Fe] = 0.4, and Y = 0.255. The determination of the distance to V69, and hence to 47 Tuc, can be further improved when infrared eclipse photometry is obtained for the variable.

• OSTI ID: 21301430
• Journal Information: Astronomical Journal (New York, N.Y. Online), Vol. 139, Issue 2; Other Information: DOI: 10.1088/0004-6256/139/2/329; Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ABUNDANCE
DISTANCE
ECLIPSE
HELIUM
IRON-ALPHA
LUMINOSITY
MASS
ORBITS
PHOTOMETRY
PROPER MOTION
STAR EVOLUTION
STARS