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Photometric studies of three multiperiodic β Cephei stars: β CMa, 15 CMa and KZ Mus
We have carried out single and multisite photometry of the three βCephei stars β and 15 CMa as well as KZ Mus. For the two stars inCMa, we obtained 270h of measurement in the Strömgren uvy andJohnson V filters, while 150h of time-resolved Strömgren uvyphotometry was acquired for KZ Mus. All three stars are multiperiodicvariables, with three (β CMa) and four (15 CMa, KZ Mus) independentpulsation modes. Two of the mode frequencies of 15 CMa are newdiscoveries and one of the known modes showed amplitude variations overthe last 33yr. Taken together, this fully explains the diverse behaviourof the star reported in the literature.Mode identification by means of the amplitude ratios in the differentpassbands suggests one radial mode for each star. In addition, βCMa has a dominant l = 2 mode while its third mode is non-radial withunknown l. The non-radial modes of 15 CMa, which are l <= 3, form analmost equally split triplet that, if physical, would imply that we seethe star under an inclination angle larger than 55°. The strongestnon-radial mode of KZ Mus is l = 2, followed by the radial mode and adipole mode. Its weakest known mode is non-radial with unknown l,confirming previous mode identifications for the pulsations of the star.The phased light curve for the strongest mode of 15 CMa has a descendingbranch steeper than the rising branch. A stillstand phenomenon duringthe rise to maximum light is indicated. Given the low photometricamplitude of this non-radial mode this is at first sight surprising, butit can be explained by the aspect angle of the mode.
| 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.
| Five-colour photometry of early-type stars in the direction of galactic X-ray sources
The results of five-color (Walraven system) photometry of 551 O- andB-type stars located in 17 fields of a few square degrees aroundgalactic X-ray sources are presented. From a comparison ofreddening-free combinations of color indices with theoretical values,calculated for model atmospheres of Kurucz (1979), effective temperatureand surface gravity for these stars are derived. In addition theirabsolute magnitude are determined by combining these parameters with theresults of evolutionary calculations of massive stars. These effectivetemperatures are in good agreement with the temperature scale ofBohm-Vitense (1981) for stars of luminosity classes II to V. For thesupergiants the effective temperatures are about 40 percent higher. Forstars of luminosity classes III to V the absolute magnitudes agree wellwith the results of independent luminosity calibrations of spectraltypes, but for brighter stars they deviate systematically. Thephotometric data are also used to study the interstellar reddening inthe direction of the X-ray sources.
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