Absolute dimensions of solar-type eclipsing binaries. III. EW Orionis. Stellar evolutionary models tested by a G0V system

Abstract

We present a detailed study of the G0V detached eclipsing binary EW Ori, based on new photometric and spectroscopic observations. Masses and radii that are precise to 0.9% and 0.5%, respectively, have been established for both components. The 1.12 Msun secondary component reveals weak Ca II H and K emission and is probably mildly active; no signs of activity are seen for the 1.17 Msun primary. We derive an [Fe/H] abundance of +0.05 +/- 0.09 and similar abundances for Si, Ca, Sc, Ti, Cr, and Ni. Yonsai-Yale and Granada solar-scaled evolutionary models for the observed metal abundance reproduce the components fairly well at an age of approx. 2 Gyr. Perfect agreement is, however, obtained at an age of 2.3 Gyr for a combination of a) a slight downwards adjustment of the envelope mixing length parameter for the secondary, as seen for other active solar-type stars, and b) a slightly lower helium content than prescribed by the Y-Z relations adopted for the standard model grids. The orbit is eccentric (e = 0.0758 +/- 0.0020), and apsidal motion with a 62% relativistic contribution has been detected. The apsidal motion period is U = 16300 +/- 3900 yr, and the inferred mean central density concentration coefficient, log(k_2) = -1.66 +/- 0.30, agrees marginally with model predictions. The measured rotational velocities, 9.0 +/- 0.7 (primary) and 8.8 +/- 0.6 (secondary) km/s, are in agreement with both the synchronous velocities and the theoretically predicted pseudo-synchronous velocities. Finally, the distance (175 +/- 7 pc), age, and center-of mass velocity (6 km/s) exclude suggested membership of the open cluster Collinder 70. EW Ori now belongs to the small group of solar-type eclipsing binaries with well-established astrophysical properties.

Accepted for publication in Astronomy and Astrophysics

References in corpus (7)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Geneva-Copenhagen Survey of the Solar neighbourhood II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk
• A spectroscopic study of southern (candidate) gamma Doradus stars. II. Detailed abundance analysis and fundamental parameters
• Absolute dimensions of solar-type eclipsing binaries. II. V636 Centauri: A 1.05 Msun primary with an active, cool, oversize 0.85 Msun secondary
• Accurate fundamental parameters of CoRoT asteroseismic targets: the solar-like stars HD 49933, HD 175726, HD 181420 and HD 181906
• Absolute dimensions of eclipsing binaries. XXVI. Setting a new standard: Masses, radii, and abundances for the F-type systems AD Bootis, VZ Hydrae, and WZ Ophiuchi
• Absolute dimensions of eclipsing binaries. XVII. A metal-weak F-type system, perhaps with preference for Y = 0.23-0.24

Cited by in corpus (7)

• Bayesian mass and age estimates for transiting exoplanet host stars
• Testing systematics of Gaia DR2 parallaxes with empirical surface brightness -- color relations applied to eclipsing binaries
• Determining the Age of the Kepler Open Cluster NGC 6819 With a New Triple System and Other Eclipsing Binary Stars
• Analysis of apsidal motion in eclipsing binaries using TESS data II. A test of internal stellar structure}
• The Surface Brightness--Color Relations Based on Eclipsing Binary Stars: Toward Precision Better than 1% in Angular Diameter Predictions
• Absolute dimensions of solar-type eclipsing binaries. EF Aquarii: a G0 test for stellar evolution models
• Revisiting the mass- and radius-luminosity relations for FGK main-sequence stars