This investigation presents a study of the Galactic structure toward the Norma section of the Milky Way. The field studied is located between 325{deg} and 335{deg} Galactic longitude and -8{deg} to 8{deg} Galactic latitude. New observations in the uvby{beta} system are combined with all uvby{beta} data currently available to collate a sample of 130 O and B stars. A uniform procedure is applied to obtain the color excesses and stellar distances for all of the stars in the sample. The sample is magnitude limited to about V=9.5mag and contains the brightest stars of the open clusters NGC 6087 and Ly 6, the field 2158 of Loden, the OB association Nor OB1, and stars located in the directions of R 103 and R 105.
Results are presented of Stromgren uvby(beta) photometry for 213 stars earlier than G0 and brigher than mpg of about 10.7mag in Selected Area 203. The observed area lies close to the geometric center of the Chamaeleon-Musca dark clouds complex. The results yield V, (b-y), m1, c1, and beta on the standard systems, with overall rms errors for one observation of one star of 0.010, 0.004, 0.007, 0.009, and 0.011, respectively.
Photometric color excesses and distances plus heliocentric coordinates are calculated for 3762 southern A and early-F stars. The present results, combined with those previously published for the Northern Hemisphere, complete the coverage of the spatial distribution of interstellar reddening in the entire solar neighborhood. The new reddening maps show that the interstellar matter within 300pc of the Sun forms a single very large cloud complex that is somewhat asymmetrical with respect to both the galactic center and the galactic plane. This complex is characterized by pronounced local irregularities in both density and spatial extent. The observations further indicate that (1) the cloud complex is not associated with Gould's belt; (2) there exist large regions of the sky devoid of dust; (3) interstellar reddening is negligible at the galactic poles; (4) the role of intercloud dust in the Southern Hemisphere is minor although more important than in the Northern Hemisphere; (5) the Sun is not located in a dust-free, spherically symmetric bubble as previously thought; and (6) the Sun is, however, located in an elongated dust-free region known as the "local trough."
We present Stroemgren uvby and H_{beta}_ photometry for a set of 575 northern main sequence A type stars, most of them belonging to the Hipparcos Input Catalogue, with V from 5mag to 10mag and with known radial velocities. These observations enlarge the catalogue we began to compile some years ago to more than 1500 stars. Our catalogue includes kinematic and astrophysical data for each star. Our future goal is to perform an accurate analysis of the kinematical behaviour of these stars in the solar neighbourhood.
The {beta} Cephei stars and slowly pulsating B (SPB) stars are massive main sequence variables. The strength of their pulsational driving strongly depends on the opacity of iron-group elements. As many of those stars naturally occur in young open clusters, whose metallicities can be determined in several fundamental ways, it is logical to study the incidence of pulsation in several young open clusters. To provide the foundation for such an investigation, Stroemgren-Crawford uvby{beta} photometry of open cluster target stars was carried out to determine effective temperatures, luminosities, and therefore cluster memberships. In the course of three observing runs, uvby{beta} photometry for 168 target stars was acquired and transformed into the standard system by measurements of 117 standard stars. The list of target stars also included some known cluster and field {beta} Cephei stars, as well as {beta} Cephei and SPB candidates that are targets of the asteroseismic part of the Kepler satellite mission. The uvby{beta} photometric results are presented. The data are shown to be on the standard system, and the properties of the target stars are discussed: 140 of these are indeed OB stars, a total of 101 targets lie within the {beta} Cephei and/or SPB star instability strips, and each investigated cluster contains such potential pulsators. These measurements will be taken advantage of in a number of subsequent publications.
We present CCD uvby{beta} photometry for stars in the nuclei of the young double cluster {h} and {chi} Persei. We find that the reddening is highly variable through the {h} Per nucleus, increasing from west to east, with values ranging from E(b-y)=0.328+/-0.022 in the western part to E(b-y)=0.465+/-0.025 in the south-east. Towards {chi} Persei the reddening is fairly constant, with E(b-y)=0.398+/-0.025. Both clusters share a common distance modulus of 11.7+/-0.1mag, and an age of logt=7.10+/-0.05 years.
