Absolute dimensions of eclipsing binaries

Abstract

Context. Precise stellar masses and radii provide unique information on stellar evolution. In a Galactic context, they may also provide information on the evolution of the Solar neighbourhood. Aims. We aim to determine absolute dimensions for the mid B-type eclipsing binary U Ophiuchi and compare the inferred ages and chemical compositions to those of other binary stars with masses near 5 M . Methods. We determine masses, radii, log g, log T eff , and luminosities for the stars in U Oph from new radial velocities and uvby light curves. By improving the Wilson-Devinney code, we also derive precise apsidal-motion and light-time orbits of this triple system, using 353 times of minimum over 120 years. Finally, we compare the data for U Oph and three similar systems with the predictions of stellar models. Results. The stars in U Oph have masses of 5.27 ± 0.09 M and 4.74 ± 0.07 M , radii of 3.48 ± 0.02 R and 3.11 ± 0.03 R ; we argue that systematic errors are negligible. The apsidal motion period is exceptionally short, U ∼ 21 yr, while the light-time orbit has P 3 ∼ 38.4 yr. The precise log g values for DI Her, U Oph, V760 Sco, and MU Cas, all within 10% of 5 M , place them successively from the ZAMS to the TAMS, at ages of 5−100 × 10 6 yr. Current stellar evolution models fit both stars in each system very well if the (otherwise unconstrained) metal abundance Z is adjusted in each case. Conclusions. More accurate data and/or binary systems with larger mass ratios are needed to actually test stellar models near 5 M . The different Z values found for these young, nearby systems suggest that disk stars form with a range of metal abundances even today, but more data are needed to confirm this result.

Absolute Properties of the Eclipsing Binary System Aq Serpentis: A Stringent Test of Convective Core Overshooting in Stellar Evolution Models

“…Of these, 39 timings are based on eclipse events with reasonably good coverage, i.e., with observations on both the ascending and descending branches of the primary or secondary minima. These were measured using either the traditional Kwee & van Woerden (1956) method (KvW) or a parabolic fit, or with an alternate technique relying on fitting a synthetic light-curve model to the observations, with the model being computed using the Wilson-Devinney (W-D) code (Wilson & Devinney 1971) and subsequent improvements by Vaz et al (2007) pertaining to the ephemeris determination. For the latter method we held all light-curve parameters fixed to values close to our final solutions reported later, and adjusted only the time of eclipse.…”

Does convective core overshooting depend on stellar mass?

“…The second system is included for a similar reason: there are very few systems with masses in the region of 5 M with good determination of their absolute dimensions. Moreover, this system was recently reanalysed together with other three systems with similar masses (Vaz et al 2007). The implications of this new analysis on the present paper will be discussed in Sect.…”

Absolute Properties of the Spotted Eclipsing Binary Star Cv Boötis

“…We used a version of the WD modeling program (Wilson & Devinney 1971;Wilson 1979Wilson , 1993) with extensive modifications as described in Vaz et al (2007) and references given therein. The modifications pertinent to CV Boo include the capability to use model atmospheres (now also available in the distributed versions of WD), consistency checks between various parameters, and the ability to use the downhill simplex algorithm (Nelder & Mead 1965) instead of differential corrections.…”