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New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
| Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
| Red and infrared colours of B stars and the reddening law in the Galaxy
The red and infrared intrinsic colours of B stars are derived fromphotometric observations through the UBV(RI)_CJHK and Hβ filters of257 early-type stars. Those stars for which the UBV and Hβmeasurements match the published spectral class, and which show no othersigns of peculiarity, are used to determine the intrinsic photometriccolours of B stars in the red and infrared. From these intrinsic coloursthe interstellar reddening relationships for the red and infraredcolours are evaluated, and the results are compared with previousestimates of these quantities. The values of R, E(B-V) and the distanceare then determined for the individual stars. R is confirmed to be closeto 3.1 in most cases, but was found to be much larger in somedirections. The relationship between R and the location of a star in theGalaxy is investigated. Usually the abnormally reddened stars seemed tobe associated with known regions of star formation. The paper alsoidentifies seven likely variable stars and a number of stars withpossible dust shells.
| Uvby-beta observations of 528 type B stars with V between the 8th and 9th magnitude
The paper presents uvby-beta measurements of 528 type B stars selectedfrom the SAO Catalog on the basis of two criteria: the spectral types inthe range B3-B5 and mV between the 8th and the 9th magnitude. Reddeningindependent (c1) values are estimated from the spectral classificationand compared to the observed values. No systematic trend with observed(b-y), H-beta, or spectral type appears to be present, but the range of(c1) residuals is surprisingly large. A rather large part of the starshas small beta values, smaller than for the BIa supergiants. Only twoare classified as O stars and most of them have the suffix e, ne, ornne. Most beta values for the O type stars are slightly above the upperlimit of 2.585 m.
| 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.
| Optical observations of ultraviolet objects. I - Spectral classification of 103 stars /l = 200-275 deg/
Results are presented of a program of spectral classification of 103stars originally selected as ultraviolet objects from TD-1 satellitephotometry with the S2/68 experiment. Most of the objects appear to bespectroscopically normal stars; the method of selection yielded a sampleof relatively unreddened B stars at distances up to about 2 kpc. Thisresult is compared with recent studies of the spatial distribution ofinterstellar extinction in the same regions of the sky.
| Spectral types for early-type stars observed by SKYLAB
MK spectral types are presented for 246 early-type stars observed withthe S-019 ultraviolet stellar astronomy experiment on Skylab. K-linetypes are also given where applicable, and various peculiar stars areidentified. The peculiar stars include five silicon stars, a shell star,a helium-rich star, a silicon-strontium star, a chromium-europium star,and two marginal metallic-line stars.
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