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Intermediate-Brightness Equatorial Spectrophotometric Standards
We have obtained spectral energy distributions for 41 7m 8m stars nearthe celestial equator (δ=±3°). The λλ31007600 Å spectral range is studied with a spectral resolution of 50Å. The relative rms error in the visible is 1 2%, increasing to 35% towards the edges of the wavelength interval studied. All stars arereferenced to a single standard, the circumpolar star HD 221525. Thesynthetic colors of common stars are compared with those observed infour photometric systems: U BV, W BV R, uvby, and that of the TYCHOcatalog. The program stars are recommended as secondaryspectrophotometric standards.
| UvbyHbeta_ photometry of main sequence A type stars.
We present Stroemgren uvby and Hbeta_ photometry for a set of575 northern main sequence A type stars, most of them belonging to theHipparcos Input Catalogue, with V from 5mag to 10mag and with knownradial velocities. These observations enlarge the catalogue we began tocompile some years ago to more than 1500 stars. Our catalogue includeskinematic and astrophysical data for each star. Our future goal is toperform an accurate analysis of the kinematical behaviour of these starsin the solar neighbourhood.
| Vacuum ultraviolet imagery of the Virgo cluster region
The results are reported of an experiment using the UV imager aboard anattitude-controlled S520 type sounding rocket. The total UV fluxes ofgalaxies in the Virgo Cluster as well as the flux level of the diffuseUV background around the cluster were measured. The data on NGC 4486 andNGC 4472 confirm the variation in the degree of the 'turnup' below 200nm in the energy spectrum of the total light of elliptical galaxies. Attwo-color diagram of galaxies of visual/near-UV/vacuum UV indicates thatcolors of spiral galaxies are distributed within a strip andwell-correlated with the morphological type, while elliptical galaxiesare located differently from spiral galaxies.
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