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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.
| The Carina Spiral Feature: Strömgren-Hβ photometry approach. I. The photometric data-base
A data-base collating all uvbybeta photometry available at present forO-B9 stars brighter than 10th visual magnitude in the field of theCarina Spiral Feature is presented. The completeness and homogeneity ofthe data-base are discussed.Based on CDS data.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/410/523
| Strömgren and Hβ photometry of O and B type stars in star-forming regions. III. Carina Spiral Feature
Strömgren and Hβ photometry of O and B type stars, generallybrighter than 9.5 mag is reported for the field of the Carina SpiralFeature. The observations are based on the PPM catalogue identificationsand are designed to improve the completeness of the existing uvbybetadata for the bright early-type stars in the field. We present new uvbyphotometry for 283 stars and Hβ photometry for 225 of them. Theseobservations are part of an ongoing effort to study the structure ofselected star-forming regions in the Milky Way by means of uvbybetaphotometry. A comparison of the new data to other uvbybeta data sets forthis field is presented. Based on data from the Strömgren AutomaticTelescope of the Copenhagen University Observatory, La Silla. Tables 1and 2 are only available in electronic form at the CDS via anonymous ftpto 130.79.128.5 or via http://cdsweb.u-strasbg.fr/Abstract.html
| OB Stellar Associations in the Direction of Centaurus OB2
One hundred eighty-five mostly OB and some early A-type stars aredetected at 1640 Å with the ultraviolet telescope Glazar aboardthe Mir space station in an area of about 8 deg^2 in the directiontoward the stellar association Cen OB2. The limiting stellar magnitudem_1640 of the observations is about 8.5 mag. Stellar associations atdistances of 360, 850, 1500, 2300, 2700, 4000, and 6700 pc are detectedby the study of the space distribution of 111 of the observed stars withknown spectral types. It was shown that the cluster IC 2944 is locatedat a distance of 2200 pc. It is suggested that the extinction ofemission of stars in the content of the cluster is due to small dustclouds or even to circumstellar dust shells. It is shown also that thedust matter is practically absent in the space between stellarassociations and that the extinction of some stars within stellarassociations is caused by relatively small dust clouds, in which thestars are embedded. Two of the detected stars, HD 101316 and HD 101967,are of relatively late spectral types and therefore probably have hotdwarf or subdwarf companions.
| Four-colour photometry of eclipsing binaries. XXXB. The early B-type near-contact binary LZ Centauri.
LZ Cen is a double-lined, near-contact but detached eclipsing binaryconsisting of two evolved early B stars (B0.5-B1). This paper presentsthe first photoelectric and spectroscopic analysis of the system, basedon new light curves and spectroscopic data. uvby light curves wereobtained with the Danish 50 cm telescope at ESO, La Silla (916 points ineach colour). They were analysed with both the WINK model (Wood 1971,1972) and the Wilson-Devinney (1971) program in its extended versions(Wilson 1979, 1993), adopting a circular orbit. The codes of both modelswere improved with modifications in the numerical solution procedure,and the Wilson-Devinney model has been implemented with the possibilityof using tables of model atmosphere calculations, following the samephilosophy as the WINK model. These modifications are documented here insome detail for future reference. The mass and luminosity ratios androtations in the system are determined from a few photographic and CCDspectra. They show that the hotter component, eclipsed at primaryeclipse, is also the smaller, less massive, and less luminous of the twostars. It was found difficult to obtain light curve solutions which wereconsistent with both the observed mass and luminosity ratios, but withthe small number of spectra available, our best compromise solutionyields M_A_=12.5Msun_, M_B_=13.5Msun_(+/-10%),R_A_=8.4Rsun_, and R_B_=9.1Rsun_(+/-3-4%). Bothstars have temperatures close to 26500K and luminositiesL_A_=3.1x10^4^Lsun_ and L_B_=3.6x10^4^Lsun_. Withlog g values as low as 3.66, the stars are obviously quite evolved andnear the end of their life on the main sequence. We have explored thelikely evolutionary state of LZ Cen in more detail by comparing itsobserved properties with the standard and overshooting models of Claret& Gimenez (1989, 1992). The analysis shows that both stars in LZ Cenhave evolved to the very point of central hydrogen exhaustion or beyondif standard models are assumed, while LZ Cen is still well within themain-sequence band of the overshooting models, a rather more plausiblescenario. In the latter case, models with Z=~0.01 fit the observedtemperatures best for an age of some 12x10^6^yr, consistent with otherrecent results on young B stars.
| Four-colour photometry of eclipsing binaries. XXXA. Light curves of LZ Centauri.
Complete uvby light curves of the detached double-lined early B-typeeclipsing binary LZ Centauri are presented. They contain 916 points ineach colour and were obtained 1982-84. A detailed photometric analysisbased on these observations and on new spectroscopic material will bepublished separately (Vaz et al. 1995).
| A homogeneous catalog of new UBV and H-beta photometry of B- and A-type stars in and around the Scorpius-Centaurus OB association
B- and A-type stars in and near the Sco-Cen OB association areinvestigated with UBV and H-beta photometry to acquire data relevant tothe luminosity function of Sco-Cen. The measurements generally consistof two 10-s integrations of U, B, V, (W, N) filters, and theobservations are corrected iteratively for atmospheric extinction andinstrumental response. The data presented give the mean V magnitude,mean B-V, mean U-B, and the estimated uncertainties for these values.The catalog provides a homogeneous catalog of data for a large fieldwith stellar objects delineating membership to the association Sco-Cenand that affect the luminosity function of the aggregate.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
| Four-colour photometry of eclipsing binaries. XXIB - Light curves of V346 Centauri
uvby light curves of the highly eccentric eclipsing binary V346 Cen arepresented (simultaneous uvby observations, 1056 in each colour). Thesystem is a detached early type binary showing total eclipse atsecondary minimum. A detailed analysis based on these light curves ispublished separately.
| Four-colour photometry of eclipsing binaries. XXIA Photometric analysis and apsidal motion study of V346 Centauri
New accurate uvby light curves obtained in 1982 and 1983 with the 50 cmDanish La Silla ESO telescope of the detached early B-type eclipsingbinary V 346 Cen have been analyzed and photometric elements calculatedusing the Wood (1982) model. An improved ephemeris and reliabledetermination of the apsidal motion period have been obtained, with aclose to 0.5 radii ratio, an orbital inclination near 84 deg, a high0.288 orbital eccentricity, and a 321 + or - 16 yr period of periastronrevolution. Improved spectroscopic orbital element estimates areprovided by supplementary spectroscopic observations, with largertemperature (26,500 and 24,000 K) and mass (12 and 8 solar masses)values than earlier estimates. Good agreement with stellar structuremodels of typical chemical composition is found, and data indicate anage of 10 million years, and show the primary to be evolved past the endof the main-sequence phase, while the secondary is essentiallyunevolved.
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