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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.
| The neutron star in the supernova remnant PKS 1209-52
We re-analyzed X-ray data collected with the ROSAT and ASCAobservatories on a candidate neutron star (NS) near the center of thesupernova remnant PKS 1209-52. We fitted the observed spectra with NSatmosphere models. The hydrogen atmosphere fits yield more realisticparameters of the NS and the intervening hydrogen column than thetraditional blackbody fit. In particular, for a NS of mass 1.4 M_sun andradius 10 km, we obtained a NS surface temperature T_eff=(1.4-1.9)x10(6) K and distance d=1.6-3.3 kpc versus T=(4.2-4.6)x 10(6) K andimplausibly large d=11-13 kpc for the blackbody fit, at a 90% confidencelevel. Our fits suggest that the surface magnetic field is either veryweak, Braisebox {-.6ex 10(10) G, or it exceeds =~ 2x 10(12) G. Thehydrogen column density inferred from the atmosphere fits, n_H=(0.7-2.2)x 10(21) cm(-2) , agrees fairly well with independent estimatesobtained from UV observations of nearby stars, radio data, and X-rayspectrum of the shell of the supernova remnant, whereas the blackbodyand power-law fits give considerably lower and greater values,n_H=(0.2-0.4)x 10(21) and (5.2-7.0)x 10(21) cm(-2) , respectively. TheNS surface temperature inferred from the atmosphere fits is consistentwith standard NS cooling models.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| An IUE survey of interstellar H I LY alpha absorption. 1: Column densities
We measure Galactic interstellar neutral hydrogen column densities byanalyzing archival interstellar Ly alpha absorption line data toward 554B2 and hotter stars observed at high resolution with the IUE satellite.This study more than doubles the number of lines of sight with measuresof N(H I) based on Ly alpha. We have included the scattered lightbackground correction algorithm of Bianchi and Bohlin in our datareduction. We use the correlation between the Balmer discontinuity(c1) index and the stellar Ly alpha absorption in order toassess the effects of stellar Ly alpha contamination. Approximately 40%of the B stars with measured (c1) index, exhibit seriousstellar Ly alpha contamination. One table contains the derived values ofthe interstellar N(H I) for 393 stars with at most small amounts ofstellar contamination. Another lists the observed values of total N(H I)for 161 stars with suspected stellar Ly alpha contamination and/oruncertain stellar parameters.
| On the origin of intermediate-latitude OB stars
An attempt is made to trace the origin of early-type stars observed atappreciable distances from the galactic plane. Because uncertainties inthe proper motions make space motions and hence dynamical lifetimesrather inaccurate, a theory of oscillations normal to the plane has beenused to compute radial velocities for 138 intermediate-latitude OBstars. These theoretical values are then compared with the observedradial velocities, and it is found that the low-velocity stars wereprobably ejected from the plane some time after formation, while thehigh-velocity stars were ejected very soon after formation. Velocitiesof ejection perpendicular to the plane are computed and show a narrowdistribution with a mean absolute value of 7 km/s together with a spreadof velocities from about 40 to over 200 km/s. The data are in reasonableagreement with a 'sling' effect and 'runaway' origin for the stars inthe sample.
| H-beta photometry of southern early-type stars and galactic structure away from the plane
H-beta photoelectric photometry is reported for 165 early-type stars atintermediate and high galactic latitudes. The data are combined withearlier UBV and spectroscopic results to determine the stellar spacedistribution. Stars of type B2 and earlier, at distances of up to 1 kpcfrom the galactic plane, appear to follow spiral structure in the plane.The available material, particularly the derived color excesses, is usedto select a number of blue stars which may be subluminous.
| Equivalent widths and rotational velocities of southern early-type stars
Not Available
| UBV photometry of southern early-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974MNRAS.168..451H&db_key=AST
| Radial velocities of Southern B stars determined at the Radcliffe Observatory.
Not Available
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| Takýmyýldýz: | Erbogan |
| Sað Açýklýk: | 12h52m30.71s |
| Yükselim: | -52°40'02.4" |
| Görünürdeki Parlaklýk: | 7.834 |
| Uzaklýk: | 2222.222 parsek |
| özdevim Sað Açýklýk: | -5.4 |
| özdevim Yükselim: | 2.8 |
| B-T magnitude: | 7.758 |
| V-T magnitude: | 7.828 |
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