The binary star NY Hya is a bright, detached, double-lined eclipsing system with an orbital period of just under five days with two components each nearly identical to the Sun and located in the solar neighbourhood. The objective of this study is to test and confront various stellar evolution models for solar-type stars based on accurate measurements of stellar mass and radius. We present new ground-based spectroscopic and photometric as well as high-precision space-based photometric and astrometric data from which we derive orbital as well as physical properties of the components via the method of least-squares minimisation based on a standard binary model valid for two detached components. Classic statistical techniques were invoked to test the significance of model parameters. Additional empirical evidence was compiled from the public domain; the derived system properties were compared with archival broad-band photometry data enabling a measurement of the system's spectral energy distribution that allowed an independent estimate of stellar properties. We also utilised semi-empirical calibration methods to derive atmospheric properties from Strömgren photometry and related colour indices. Data was used to confront the observed physical properties with classic and magnetic stellar evolution models.

Context. Double-lined, detached eclipsing binaries are our main source for accurate stellar masses and radii. In this paper we focus on the 1.15-1.70 M(circle dot) interval where convective core overshoot is gradually ramped up in theoretical evolutionary models. Aims. We aim to determine absolute dimensions and abundances for the F-type detached eclipsing binary BK Peg, and to perform a detailed comparison with results from recent stellar evolutionary models, including a sample of previously studied systems with accurate parameters.Methods. uvby light curves and uvby beta standard photometry were obtained with the Stromgren Automatic Telescope, ESO, La Silla, and high-resolution spectra were acquired with the FIES spectrograph at the Nordic Optical Telescope, La Palma.Results. The 5(d).49 period orbit of BK Peg is slightly eccentric (e = 0.053). The two components are quite different with masses and radii of (1.414 +/- 0.007 M(circle dot), 1.988 +/- 0.008 R(circle dot)) and (1.257 +/- 0.005 M(circle dot), 1.474 +/- 0.017 R(circle dot)), respectively. The measured rotational velocities are 16.6 +/- 0.2 (primary) and 13.4 +/- 0.2 (secondary) kms(-1). For the secondary component this corresponds to (pseudo) synchronous rotation, whereas the primary component seems to rotate at a slightly lower rate. We derive an iron abundance of [Fe/H] = -0.12 +/- 0.07 and similar abundances for Si, Ca, Sc, Ti, Cr and Ni. The stars have evolved to the upper half of the main-sequence band. Yonsei-Yale and Victoria-Regina evolutionary models for the observed metal abundance reproduce BK Peg at ages of 2.75 and 2.50 Gyr, respectively, but tend to predict a lower age for the more massive primary component than for the secondary. We find the same age trend for three other upper main-sequence systems in a sample of well studied eclipsing binaries with components in the 1.15-1.70 M(circle dot) range. We also find that the Yonsei-Yale models systematically predict higher ages than the Victoria-Regina models. The sample includes BW Aqr, and as a supplement we have determined a [Fe/H] abundance of -0.07 +/- 0.11 for this late F-type binary.Conclusions. We propose to use BK Peg, BW Aqr, and other well-studied 1.15-1.70 M(circle dot) eclipsing binaries to fine-tune convective core overshoot, diffusion, and possibly other ingredients of modern theoretical evolutionary models.

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.

Context. Double-lined, detached eclipsing binaries are our main source for accurate stellar masses and radii. This paper is the first in a series with focus on the upper half of the main-sequence band and tests of 1-2 Mevolutionary models. Aims. We aim to determine absolute dimensions and abundances for the detached eclipsing binary V1130 Tau, and to perform a de- tailed comparison with results from recent stellar evolutionary models. Methods. uvby light curves and uvbyβ standard photometry have been obtained with the Stromgren Automatic Telescope, and high-resolution spectra have been acquired at the FEROS spectrograph; both are ESO, La Silla facilities. We have applied the Wilson-Devinney model for the photometric analysis, spectroscopic elements are based on radial velocities measured via broad- ening functions, and (Fe/H) abundances have been determined from synthetic spectra and uvby calibrations. Results. V1130 Tau is a bright (mV = 6.56), nearby (71 ± 2 pc) detached system with a circular orbit (P = 0. d 80). The components are deformed with filling factors above 0.9. Their masses and radii have been established to 0.6-0.7%. We derive a (Fe/H) abundance of −0.25 ± 0.10. The measured rotational velocities, 92.4 ± 1.1 (primary) and 104.7 ± 2.7 (secondary) km s −1 , are in fair agreement with synchronization. The larger 1.39 Msecondary component has evolved to the middle of the main-sequence band and is slightly cooler than the 1.31 Mprimary. Yonsai-Yale, BaSTI, and Granada evolutionary models for the observed metal abundance and a "normal" He content of Y = 0.25−0.26, marginally reproduce the components at ages between 1.8 and 2.1 Gyr. All such models are, however, systematically about 200 K hotter than observed and predict ages for the more massive component, which are systematically higher than for the less massive component. These trends can not be removed by adjusting the amount of core overshoot or envelope convection level, or by including rotation in the model calculations. They may be due to proximity effects in V1130 Tau, but on the other hand, we find excellent agreement for 2.5-2.8 Gyr Granada models with a slightly lower Y of 0.23-0.24. Conclusions. V1130 Tau is a valuable addition to the very few well-studied 1-2 Mbinaries with component(s) in the upper half of the main-sequence band, or beyond. The stars are not evolved enough to provide new information on the dependence of core overshoot on mass (and abundance), but might - together with a larger sample of well-detached systems - be useful for further tuning of the helium enrichment law. Analyses of such systems are in progress.

V1130 Tau is a bright (m_V = 6.56), nearby (71 +/- 2 pc) detached system with a circular orbit (P = 0.80d). The components are deformed with filling factors above 0.9. Their masses and radii have been established to 0.6-0.7%. We derive a [Fe/H] abundance of -0.25 +/- 0.10. The measured rotational velocities, 92.4 +/- 1.1 (primary) and 104.7 +/- 2.7 (secondary) km/s, are in fair agreement with synchronization. The larger 1.39 Msun secondary component has evolved to the middle of the main-sequence band and is slightly cooler than the 1.31 Msun primary. Yonsai-Yale, BaSTI, and Granada evolutionary models for the observed metal abundance and a 'normal' He content of Y = 0.25-0.26, marginally reproduce the components at ages between 1.8 and 2.1 Gyr. All such models are, however, systematically about 200 K hotter than observed and predict ages for the more massive component, which are systematically higher than for the less massive component. These trends can not be removed by adjusting the amount of core overshoot or envelope convection level, or by including rotation in the model calculations. They may be due to proximity effects in V1130 Tau, but on the other hand, we find excellent agreement for 2.5-2.8 Gyr Granada models with a slightly lower Y of 0.23-0.24. V1130 Tau is a valuable addition to the very few well-studied 1-2 Msun binaries with component(s) in the upper half of the main-sequence band, or beyond. The stars are not evolved enough to provide new information on the dependence of core overshoot on mass (and abundance), but might - together with a larger sample of well-detached systems - be useful for further tuning of the helium enrichment law.

V1130 Tau is a bright (m_V = 6.56), nearby (71 +/- 2 pc) detached system with a circular orbit (P = 0.80d). The components are deformed with filling factors above 0.9. Their masses and radii have been established to 0.6-0.7%. We derive a [Fe/H] abundance of -0.25 +/- 0.10. The measured rotational velocities, 92.4 +/- 1.1 (primary) and 104.7 +/- 2.7 (secondary) km/s, are in fair agreement with synchronization. The larger 1.39 Msun secondary component has evolved to the middle of the main-sequence band and is slightly cooler than the 1.31 Msun primary. Yonsai-Yale, BaSTI, and Granada evolutionary models for the observed metal abundance and a 'normal' He content of Y = 0.25-0.26, marginally reproduce the components at ages between 1.8 and 2.1 Gyr. All such models are, however, systematically about 200 K hotter than observed and predict ages for the more massive component, which are systematically higher than for the less massive component. These trends can not be removed by adjusting the amount of core overshoot or envelope convection level, or by including rotation in the model calculations. They may be due to proximity effects in V1130 Tau, but on the other hand, we find excellent agreement for 2.5-2.8 Gyr Granada models with a slightly lower Y of 0.23-0.24. V1130 Tau is a valuable addition to the very few well-studied 1-2 Msun binaries with component(s) in the upper half of the main-sequence band, or beyond. The stars are not evolved enough to provide new information on the dependence of core overshoot on mass (and abundance), but might - together with a larger sample of well-detached systems - be useful for further tuning of the helium enrichment law.

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.

Context. Accurate mass, radius, and abundance determinations from binaries provide important information on stellar evolution, fundamental to central fields in modern astrophysics and cosmology.Aims. Within the long-term Copenhagen Binary Project, we aim to obtain high-quality light curves and standard photometry for double-lined detached eclipsing binaries with late A, F, and G type main-sequence components, needed for the determination of accurate absolute dimensions and abundances, and for detailed comparisons with results from recent stellar evolutionary models.Methods. Between March 1985 and July 2007, we carried out photometric observations of ADBoo, HWCMa, SWCMa, V636 Cen, VZHya, and WZOph at the Stromgren Automatic Telescope at ESO, La Silla.Results. We obtained complete uvby light curves, ephemerides, and standard uvby beta indices for all six systems. For V636 Cen and HWCMa, we present the first modern light curves, whereas for ADBoo, SWCMa, VZ Hya, and WZ Oph, they are both more accurate and more complete than earlier data. Due to a high orbital eccentricity (e = 0.50), combined with a low orbital inclination (i = 84.. 7), only one eclipse, close to periastron, occurs for HWCMa. For the two other eccentric systems, V636 Cen (e = 0.134) and SWCMa (e = 0.316), apsidal motion has been detected with periods of 5270 +/- 335 and 14 900 +/- 3600 years, respectively.

Aims In order to increase the limited number of B-stars with accurately known dimensions, and also the number of well studied eclipsing binaries in open clusters, we have undertaken observations and studies of four southern double-lined eclipsing B-type binaries; DW Car, BF Cen, ACVel, and NSV 5783.Methods. Complete uvby light curves were observed between January 1982 and April 1991 at the Danish 0.5 m telescope at ESO La Silla, since 1985 known as the Stromgren Automatic Telescope ( SAT). Standard indices for the systems and the comparison stars, as well as additional minima observations for ACVel, have been obtained later at SAT. For DWCar and ACVel, high-resolution spectra for definitive spectroscopic orbits have also been obtained; they are presented as part of the detailed analyses of these systems. A few spectra of NSV 5783 are included in the present paper.Results. For all four systems, the first modern accurate light curves have been established. DWCar is a detached system consisting of two nearly identical components. It is member of the young open cluster Cr228. A detailed analysis, based on the new light curves and 29 high-resolution spectra, is published separately. BFCen is semidetached and is member of NGC 3766. Modern spectra are needed for a detailed study. ACVel is a detached system with at least one more star. A full analysis, based on the new light curves and 18 high-resolution spectra, is published separately. NSV 5783 is discovered to be an eclipsing binary consisting of two well-detached components in an 11-day period eccentric (e = 0.18) orbit. Secondary eclipse is practically total. From the light curves and a few high-resolution spectra, accurate photometric elements and preliminary absolute dimensions have been determined. The quite similar components have masses of about 5 M-circle dot and radii of about 3.5 R-circle dot, and they seem to have evolved just slightly off the ZAMS. The measured rotational velocities (approximate to 150 km s(-1)) are about 6 times those corresponding to pseudosynchronization.

New extensive differential uvby photometry at the Danish SAT telescope, and high-resolution spectroscopy at ESO, SAAO and Mt. John Observatory reveal that HD 123335 (HR 5292) is an eclipsing SB2 consisting of two sharp-lined B-type stars in an eccentric orbit (e = 0.735, P-orb = 35(d)44735). The slowest rotating component (P-rot = 61.(d)46) is a chemically peculiar (CP) star of the type He-weak SrTi.

AC Vel has two B-type eclipsing components, and the presence of a third component is indicated by: 1) light-time effects, and 2) the need for about ten per cent third light in the photometric solutions. The wide orbit is derived from the light-time effect and provides a surprisingly high lower limit to the mass of the third component, indicating that this component is multiple. We present the disentangling of the binary component spectra, and the identification of the third component in the Balmer hydrogen lines.