Four-colour photometry of eclipsing binaries

Abstract

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, AC Vel, 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 Strömgren Automatic Telescope (SAT). Standard indices for the systems and the comparison stars, as well as additional minima observations for AC Vel, have been obtained later at SAT. For DW Car and AC Vel, 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. DW Car 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. BF Cen is semidetached and is member of NGC 3766. Modern spectra are needed for a detailed study. AC Vel 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 and radii of about 3.5 R , and they seem to have evolved just slightly off the ZAMS. The measured rotational velocities (≈150 km s −1 ) are about 6 times those corresponding to pseudosynchronization.

The Eclipsing Binary V1061 Cygni: Confronting Stellar Evolution Models for Active and Inactive Solar‐Type Stars

“…For stars less massive than the Sun properties such as the stellar radius and the effective temperature have occasionally been found to disagree with model predictions (see, e.g., Lacy 1977;Popper 1997;Clausen et al 1999a;Torres & Ribas 2002;Ribas 2003). Directed efforts to find additional systems in this regime suitable for testing theory (Popper 1996;Clausen et al 1999b) have produced a few cases, while other examples have been found serendipitously (e.g., Creevey et al 2005;López-Morales & Ribas 2005). The present binary system is in the second category, since it was originally thought to be of a completely different nature.…”

GU Monocerotis: A high-mass eclipsing overcontact binary in the young open cluster Dolidze 25

“…The overcontact system V701 Sco, which is discussed below, contains two identical stars with mass ≈10.2 M (Table 5). Among detached binaries, one of the best examples is DW Car, which is a member of the very young open cluster Collinder 228, whose components were both classified as B1 V. With an orbital period of 1.3 d, they have masses of 11.34 ± 0.12 and 10.63 ± 0.14 M (Southworth & Clausen 2007;Clausen et al 2007). This object is almost certainly a pre-contact binary, and both components still seem to be very compact, as References.…”

The Banana Project. Iv. Two Aligned Stellar Rotation Axes in the Young Eccentric Binary System Ep Crucis: Primordial Orientation and Tidal Alignment

“…In addition the apsidal motion is not measured yet and we cannot calculate it from the known system parameters as it depends on the true stellar obliquity and not only the sky projection (Shakura 1985;Albrecht et al 2009). Thus we do not use the photometric values on T minI, and ω as priors and we only use the measurements of P and e by Clausen et al (2007) as prior constraints. We revisit this subject in Section 4.3.…”

“…The photometric character of the eclipses are specified by another set of parameters: the light ratio between the two stars at the wavelength of interest (L s /L p at 4480 Å), the quadratic limb darkening parameters (u1 i and u2 i ), the fractional radii of the stars (r i ), and the orbital inclination (i o ), for which we step in cos i o . For the fractional radii and the orbital inclination we use prior information from Clausen et al (2007). For L s /L p we use their results in the b band.…”

“…There is one important difference between the two systems: the age of the stars. Clausen et al (2007) estimated an age of ≈ 50 Myr for the two stars in the EP Cru system while DI Her is essentially a Zero Age Main Sequence (ZAMS) system with an estimated age of 4.5 ± 2.5 Myr (Claret et al 2010). Therefore by studying EP Cru we have the opportunity to learn if according to our current understanding of binary evolution one system is simply an older version of the other, or if they had different childhoods altogether.…”