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Interstellar Reddening in the Southern Hemisphere. II. Analysis of the uvby-Beta Observations
Photometric color excesses and distances plus heliocentric coordinatesare calculated for 3,762 southern A and early F stars. The presentresults, combined with those previously published for the northernhemisphere, complete the coverage of the spatial distribution ofinterstellar reddening in the entire solar neighborhood. The newreddening maps show that the interstellar matter within 300 pc of theSun forms a single very large cloud complex that is somewhatasymmetrical with respect to both the galactic center and the galacticplane. This complex is characterized by pronounced local irregularitiesin both density and spatial extent. The observations further indicatethat (1) the cloud complex is not associated with Gould's belt; (2)there exist large regions of the sky devoid of dust; (3) interstellarreddening is negligible at the galactic poles; (4) the role ofintercloud dust in the southern hemisphere; (5) the Sun is not locatedin a dust-free, spherically symmetric bubble as previously thought; and(6) the Sun is, however, located in an elongated dust-free region knownas the "local trough.". (SECTION: Interstellar Medium and Nebulae)
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
| Uvby-beta photometry of stars in the Michigan Spectral Catalogue. I - The Delta Del stars
uvby-beta photometry of 74 stars classified as Delta Del in Volume 1 ofthe Michigan Spectral Catalogue is presented. The photometry is inagreement with the spectral classification in that it indicates DeltaDel stars are metal-line-enhanced stars with equivalent-temperaturetypes of A9 + or - 2 subtypes. There is a discrepancy between theluminosity implied from the delta c1 index and the spectralclassification. It is argued that c1 is an inadequateluminosity indicator for some late A- to early F-type stars. Several ofthe Delta Del stars are known Delta Scuti pulsators, and some commentson the metallicism-pulsation relation are made.
| Estimation of spectral classifications for bright southern stars with interesting Stromgren indices
This paper investigates the degree of success with which uvby photometrycan be applied to predict spectral classifications for 947 A, F, and Gstars brighter than an apparent magnitude of 8.3 and with four-colorindices indicating some kind of interesting, unusual, or peculiarspectrum. One or several possible spectral classifications are estimatedfor each star from photometry alone, double stars are distinguished, andthe estimates are compared with published classifications. The resultsshow that the framework provided by uvby photometry can be extended toinclude most G and K stars, reddened stars, peculiar stars, and certaintypes of double star.
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