Oscillating Blue Stragglers, gamma Doradus stars and eclipsing binaries in the open cluster NGC2506

Abstract

This is the first step in a project to combine studies of eclipsing binaries and oscillating stars to probe the interior of Blue Stragglers (BS). This may imply a way to discriminate observationally between different birth mechanisms of BS stars. We study the open cluster NGC2506 which contains oscillating BS stars and detached eclipsing binaries for which accurate parameters can be derived. This will tightly constrain the cluster isochrone and provide an absolute mass, radius and luminosity-scale for the cluster stars along with the cluster age, metallicity and distance. The present work focuses on obtaining the light curves of the binaries and determine their orbital periods, on obtaining power spectra of the oscillating BS stars to select targets for follow-up studies, and on searching for gamma Doradus type variables which are also expected to be present in the cluster. With a two-colour, dual-site photometric campaign we obtained 3120 CCD-images of NGC2506 spread over four months. We analysed the BI time-series of the oscillating stars and used simulations to derive statistical uncertainties of the resulting frequencies, amplitudes and phases. A preliminary mode-identification was performed using frequency ratios for the oscillating BS stars, and amplitude ratios and phase differences for a population of newly detected gamma Doradus stars. We quadrupled the number of known variables in NGC2506 by discovering 3 new oscillating BS stars, 15 gamma Doradus stars and four new eclipsing binaries. The orbital periods of 2 known, detached eclipsing binaries were derived. We discovered a BS star with both p-mode and g-mode variability and we confronted our gamma Doradus observations with state-of-the-art seismic models, but found significant discrepancy between theory and observations.

17 pages, 20 figures, accepted for publication in A&A

References in corpus (4)

• Discovery of Carbon/Oxygen depleted Blue Straggler Stars in 47 Tucanae: the chemical signature of a mass-transfer formation process
• The radial distribution of blue straggler stars and the nature of their progenitors
• A new method for the spectroscopic identification of stellar non-radial pulsation modes. II. Mode identification of the Delta Scuti star FG Virginis
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Cited by in corpus (7)

• A spectroscopic study of southern (candidate) gamma Doradus stars. II. Detailed abundance analysis and fundamental parameters
• UOCS-VIII. UV Study of the open cluster NGC 2506 using ASTROSAT
• WIYN Open Cluster Study. LXXII. A uvbyCa Hbeta CCD Analysis of the Metal-Deficient Open Cluster, NGC 2506
• Extremely precise age and metallicity of the open cluster NGC 2506 using detached eclipsing binaries
• SPB stars in the open SMC cluster NGC 371
• WIYN Open Cluster Study. XC. Radial-velocity Measurements and Spectroscopic Binary Orbits in the Open Cluster NGC 2506
• Constraining the properties of delta Scuti stars using spectroscopic eclipsing binary systems