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Four-colour photometry of eclipsing binaries. XL. uvby light curves for the B-type systems DW Carinae, BF Centauri, AC Velorum, and NSV 5783
Aims.In order to increase the limited number of B-stars with accuratelyknown dimensions, and also the number of well studied eclipsing binariesin open clusters, we have undertaken observations and studies of foursouthern double-lined eclipsing B-type binaries; DW Car, BF Cen, AC Vel,and NSV 5783. Methods: .Complete {uvby} light curves were observedbetween January 1982 and April 1991 at the Danish 0.5 m telescope at ESOLa Silla, since 1985 known as the Strömgren Automatic Telescope(SAT). Standard indices for the systems and the comparison stars, aswell as additional minima observations for AC Vel, have been obtainedlater at SAT. For DW Car and AC Vel, high-resolution spectra fordefinitive spectroscopic orbits have also been obtained; they arepresented as part of the detailed analyses of these systems. A fewspectra of NSV 5783 are included in the present paper. Results:.For all four systems, the first modern accurate light curves have beenestablished. DW Car is a detached system consisting of two nearlyidentical components. It is member of the young open cluster Cr228. Adetailed analysis, based on the new light curves and 29 high-resolutionspectra, is published separately. BF Cen is semidetached and is memberof NGC 3766. Modern spectra are needed for a detailed study. AC Vel is adetached system with at least one more star. A full analysis, based onthe new light curves and 18 high-resolution spectra, is publishedseparately. NSV 5783 is discovered to be an eclipsing binary consistingof two well-detached components in an 11-day period eccentric (e = 0.18)orbit. Secondary eclipse is practically total. From the light curves anda few high-resolution spectra, accurate photometric elements andpreliminary absolute dimensions have been determined. The quite similarcomponents have masses of about 5 Mȯ and radii of about3.5 Rȯ, and they seem to have evolved just slightly offthe ZAMS. The measured rotational velocities (≈150 kms-1) are about 6 times those corresponding topseudosynchronization.
| AC Vel, a triple system. A call for observations of minima and spectra
The eclipsing binary AC Vel turns out to be at least triple. We providea first estimate of the ephemeris including light time effects and callfor further times of minima and spectra.
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