The Clusters AgeS Experiment (CASE). I. V209 omega Cen - An Eclipsing Post-Common Envelope Binary in the Globular Cluster omega Cen

Abstract

We use photometric and spectroscopic observations of the detached eclipsing binary V209 omega Cen to derive the masses, radii, and luminosities of the component stars. The system exhibits total eclipses and, based on the measured systemic velocity and the derived distance, is a member of the globular cluster omega Cen. We obtain 0.945 +/- 0.043 Msun, 0.983 +/- 0.015 Rsun and 6.68 +/- 0.88 Lsun for the cooler, but larger and more luminous primary component. The secondary component has 0.144 +/- 0.008 Msun, 0.425 +/- 0.008 Rsun and 2.26 +/- 0.28 Lsun. The effective temperatures are estimated at 9370 K for the primary and at 10866 K for the secondary. On the color-magnitude diagram of the cluster, the primary component occupies a position between the tip of the blue straggler region and the extended horizontal branch while the secondary component is located close to the red border of the area occupied by hot subdwarfs. However, its radius is too large and its effective temperature is too low for it to be an sdB star. We propose a scenario leading to the formation of a system with such unusual properties with the primary component ``re-born'' from a former white dwarf which accreted a new envelope through mass transfer from its companion. The secondary star has lost most of its envelope while starting its ascent onto the sub-giant branch. It failed to ignite helium in its core and is currently powered by a hydrogen burning shell.

24 pages, 9 figures, AJ, in press

References in corpus (22)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• A method for optimal image subtraction
• The origin of sdB stars (II)
• Optimal Techniques in Two-dimensional Spectroscopy: Background Subtraction for the 21st Century
• Variable Stars in Galactic Globular Clusters
• Ultraviolet Radiation from Evolved Stellar Populations -- I. Models
• The binary fraction of extreme horizontal branch stars
• The dynamical distance and intrinsic structure of the globular cluster omega Centauri
• Reconstructing the evolution of white dwarf binaries: further evidence for an alternative algorithm for the outcome of the common-envelope phase in close binaries
• Close binary EHB stars from SPY
• Radial Velocity Studies of Close Binary Stars.VII. Methods and Uncertainties
• Chemical Abundances and Rotation Velocities of Blue Horizontal-Branch Stars in Six Globular Clusters
• Orbital periods of twenty two subdwarf B stars
• Cluster AgeS Experiment: The Age and Distance of the Globular Cluster omega Centauri Determined from Observations of the Eclipsing Binary OGLEGC17
• A Helium White Dwarf of Extremely Low Mass
• Planets in Stellar Clusters Extensive Search. I. Discovery of 47 Low-amplitude Variables in the Metal-rich Cluster NGC 6791 with Millimagnitude Image Subtraction Photometry
• PSR J1740-5340: accretion inhibited by radio-ejection in a binary millisecond pulsar in the Globular Cluster NGC 6397
• The Age and Metallicity Relation of Omega Centauri
• The lack of close binaries among hot horizontal branch stars in NGC6752
• Cluster AgeS Experiment. Catalog of Variable Stars in the Globular Cluster Omega Centauri
• Mass distribution of DA white dwarfs in the First Data Release of the Sloan Digital Sky Survey
• Eclipsing binary millisecond pulsar PSR J1740-5340 -- evolutionary considerations and observational test

Cited by in corpus (21)

• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• EL CVn-type binaries - Discovery of 17 helium white dwarf precursors in bright eclipsing binary star systems
• The Clusters AgeS Experiment (CASE). IV. Analysis of the Eclipsing Binary V69 in the Globular Cluster 47 Tuc
• Discovery of a stripped red giant core in a bright eclipsing binary system
• Blue Straggler masses from pulsation properties. I. The case of NGC6541
• On the RR Lyrae stars in globulars: IV. $\omega$ Centauri Optical UBVRI Photometry
• A Catalogue of Potential Post Common Envelope Binaries
• The cluster ages experiment (CASE). V. Analysis of three eclipsing binaries in the globular cluster M4
• Discovery of 36 eclipsing EL CVn binaries found by the Palomar Transient Factory
• On the RR Lyrae stars in globulars: V. the complete Near-Infrared (JHKs) census of omega Centauri RR Lyrae variables
• BEER analysis of Kepler and CoRoT light curves: IV. Discovery of four new low-mass white dwarf companions in the Kepler data
• RR Lyrae variables in Messier 53: Near-infrared Period--Luminosity relations and the calibration using Gaia Early Data Release 3
• On a new method to estimate distance, reddening and metallicity of RR Lyrae stars using optical/near-infrared ($B$,$V$,$I$,$J$,$H$,$K$) mean magnitudes: $\omega$ Centauri as a first test case
• SHOTGLAS I: The ultimate spectroscopic census of extreme horizontal branch stars in $\omega$ Centauri
• Orbital properties of an unusually low-mass sdB star in a close binary system with a white dwarf
• Metal-Rich SX Phe stars in the Kepler Field
• MOCCA code for star cluster simulations - V. Initial globular cluster conditions influence on blue stragglers
• A possible formation channel for blue hook stars in globular cluster - II. Effects of metallicity, mass ratio, tidal enhancement efficiency and helium abundance
• Evolutionary history of four binary blue stragglers from the globular clusters ωCen, M55, 47 Tuc and NGC 6752
• A VIMOS spectroscopy of photometric variables and straggler candidates in omega Centauri
• Low-mass and sub-stellar eclipsing binaries in stellar clusters