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On the infrared void in the Lupus dark clouds
Strömgren uvbyβ photometry observations obtained for 205 starsin the general direction of a void in the IRAS 100-μm emission fromthe Lupus dark cloud complex are presented and analysed. The colourexcess versus distance diagram confirms the existence of a regiondepleted from interstellar material, which is also seen in the ROSATsoft X-ray background emission map. The distance to the surroundingmaterial is estimated as being within the interval from 60 to 100pc.This result is in disagreement with previous distance estimates to thesupposed supernova that has been suggested as responsible for clearingthe region from dust. As an alternative, the data presented support thesuggestion that the void may have been produced by the detachment ofmaterial from the interface between LoopI and the Local Bubble as aconsequence of hydromagnetic instabilities. Moreover, the distributionof colour excess as a function of distance supports a value of ~150pc asthe most probable distance to the dark cloud known as Lupus1.
| 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)
| 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.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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