Strömgren H? Photometry of O and B Stars in Norma
This investigation presents a study of the Galactic structure toward theNorma section of the Milky Way. The field studied is located between325° and 335° Galactic longitude and -8° to 8° Galactic latitude. New observations in the uvby? system are combined with all uvby? data currently available to collate a sample of 130 O and B stars. A uniform procedure is applied to obtain the color excesses and stellardistances for all of the stars in the sample. The sample is magnitudelimited to about V=9.5 mag and contains the brightest stars of the openclusters NGC 6087 and Ly 6, the field 2158 of Loden, the OB associationNor OB1, and stars located in the directions of R 103 and R 105. Theintrinsically luminous stars in the field studied appear to be closer tothe Sun than it has previously been thought. At about 860 pc, themajority of the stars in the sample delineate a segment consistent withthe location of the Sagittarius-Carina arm as suggested in the four-armmodel representation of the grand design of the Milky Way. A small partof the sample defines the near edge of the Scutum-Crux arm at about 1.75kpc.
|
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.
|
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.
|
Broad-band photometry of selected southern ultraviolet-bright stars.
Not Available
|
Five-colour photometry of early-type stars in the direction of galactic X-ray sources
The results of five-color (Walraven system) photometry of 551 O- andB-type stars located in 17 fields of a few square degrees aroundgalactic X-ray sources are presented. From a comparison ofreddening-free combinations of color indices with theoretical values,calculated for model atmospheres of Kurucz (1979), effective temperatureand surface gravity for these stars are derived. In addition theirabsolute magnitude are determined by combining these parameters with theresults of evolutionary calculations of massive stars. These effectivetemperatures are in good agreement with the temperature scale ofBohm-Vitense (1981) for stars of luminosity classes II to V. For thesupergiants the effective temperatures are about 40 percent higher. Forstars of luminosity classes III to V the absolute magnitudes agree wellwith the results of independent luminosity calibrations of spectraltypes, but for brighter stars they deviate systematically. Thephotometric data are also used to study the interstellar reddening inthe direction of the X-ray sources.
|
UVBY H-beta photometry of UV-bright stars
uvby H-beta photometry is presented for 90 stars taken from an earlyversion of the Carnochan and Wilson (1983) catalogue of stars that havevery negative UV colors. Two have definite UV excesses (HD 36629, and HD81307). Four early-B stars have UV colors too positive for their visibleclassification, and beta-indices that indicate higher luminosities thanappear possible on galactic distribution grounds. Six late-B starsappear to have discordant flux distributions for which there are noobvious explanations. It is suggested that the high population ofsubluminous stars derived by Carnochan and Wilson is the product of thestatistical treatment used and the extreme patchiness in theinterstellar absorption, which gives rise to large numbers oflittle-reddened stars.
|
UBV photometry for southern OB stars
New UBV photometry of 1227 OB stars in the southern Milky Way ispresented. For 1113 of these stars, MK spectral types have been reportedpreviously in a comprehensive survey to B = 10.0 mag.
|
MK spectral classifications for southern OB stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977ApJS...35..111G&db_key=AST
|
INHABITED SKY
