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Photometric and spectroscopic analysis of high Galactic latitude molecular clouds. I - Distances and extinctions of stars toward 25 selected regions
The paper presents new photoelectric photometry in the UBV, uvby, andH-beta systems for 320 stars at high Galactic latitudes, selected fortheir proximity to the densest portions of a variety of high Galacticlatitude atomic and molecular clouds. Low-resolution digital spectra areemployed to classify 115 of the stars. Several novel techniques aredeveloped for automatic digital spectral classification, and fordereddening Stromgren uvby-beta and Johnson UBV,H-beta photometry. Anempirical determination of the errors in the derived dereddened colors,and techniques for converting between the two photometric systems arepresented on the basis of the analysis of a statistically significantsample of 1480 stars with complete data sets in both photometric systemsand with an accurate MK spectral type. New constraints on the distancesto several clouds are presented.
| 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.
| Detection of a local high-velocity absorption-line system toward HD 93721
Attention is given to high-resolution spectroscopic observations of thestar HD 93721, which reveal the presence of at least 10 components of CaII absorption, ranging in velocity from -65 to +75 km/s, for a totalrange of 140 km/s. Interstellar Ca II components with N(Ca II) rangingfrom 6 x 10 exp 10 to 9.0 x 10 exp 11/sq cm are observed, whilespectroscopic observations of Na I absorption show a total of fiveinterstellar components ranging in velocity from -58 to -13 km/s, with atotal N(Na I) of 7.0 x 10 exp 11/sq cm. Low-resolution spectra for HD93721 provide a spectral type of B9.5 III, which when combined with newphotometry places the star at a distance of 410 +/- 50 pc. Examinationof both optical and IR sky-survey plates reveals the location of themain absorbing cloud at the edge of an extended filament which may beassociated with the interaction of a high-velocity cloud with the localinterstellar medium in the vicinity of the Gum Nebula.
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