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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.
| Observations of OB-stars at the former Leiden Southern Station
About 700 stars, mostly OB-stars, were observed by the author at theformer Leiden Southern Station at Hartebeespoortdam, South Africa, inthe observing seasons 1965, 1968, 1969, 1974, 1977, 1978. Observationswere made in the five channels of the Walraven photometric system. Dueto weathering of the telescope mirror the W channel gave no reliableresults for the faintest stars (m = 11 mag); in these cases the U-Wcolour index is not given. The change in sensitivity in the V channel,supposedly having occurred in 1968, was not recognised. Table~5 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/369/527
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Multicolor Polarization Study of ARA OB1
We present the results of a multicolor polarimetric study of stars inthe association Ara OB1. Several objects belonging to the clusters NGC6204, 6193, and 6167 and the local field were observed as part of aglobal study of the region. The polarimetry shows that the orientationof the polarimetric vectors of each star is very similar within eachcluster. The average values are 35.5d+/-15.1d and 52.2d+/-16 deg for NGC6204 and 6193, respectively. An average value of 106.5d+/-9.9d is foundfor NGC 6167, but the angle distribution is asymmetric, and a secondcomponent can be fitted to the angle histogram (P.A.~120.8d+/-11.6d),showing a behavior not observed in NGC 6204 and 6193. So, we suggestthat some of the observed stars perhaps belong to another starsgrouping, located behind NGC 6167 and between a dust layer with adifferent orientation of the grains. The large difference in thepolarization angle between NGC 6167 and the other two clusters couldalso be explained because NGC 6167 is supposed to be at the center of agas-expanding structure and it is possible that this cluster was theorigin of the star formation process in the Ara OB1 association,triggered by stellar winds or supernova explosions.
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| A spectroscopic database for Stephenson-Sanduleak Southern Luminous Stars
A database of published spectral classifications for objects in theStepenson-Sanduleak Luminous Stars in the Southern Milky Way catalog hasbeen compiled from the literature. A total of 6182 classifications for2562 stars from 139 sources are incorporated.
| The interstellar medium in the ARA OB1 field
We report here the results of a detailed study of two surveys of H I, atlambda = 21 cm, in the field of the stellar association Ara OB1.Subtracting the background with a procedure developed here, we were ableto identify two H I shell-like features, at roughly the same positionbut at different velocities, whose parameters were determined. On thebasis of their kinematical distances, two concentrations of OB stars(one at 1400 pc, belonging to Ara OB1, and another at 2500 pc) might bethe progenitors of these shells. The nearest H I shell may havetriggered a process of star formation.
| UBV photometry of OB+ stars in the southern Milky Way
One thousand two hundred and twenty six new observations are combinedwith previously published results of the author to yield an internalyconsistent set of magnitudes and colors on the international UBV systemfor 666 stars classified as OB+ in the Stephenson-Sanduleak OB starsurvey. The U - B, B - V diagram indicates that these stars consistprimarily of O-type stars and early B-type supergiants, reddened by upto E(B - V) = 2.1 mag.
| The distribution of OB stars and dust in a Milky Way field at (l,b) = (335 deg, 0 deg)
New photoelectric UBV photometry for 103 stars and MK spectroscopy for110 stars in a 21 sq-deg field at (l,b) = (335 deg, 0 deg) are studied,in addition to previous data for stars in this field. Most of the 112 OBstars considered may be separated into three groups associated with thespiral structure of the inner galaxy: one at 1.34 + or - 0.05 kpc, oneat 2.41 + or - 0.08 kpc, and one at 3.69 + or - 0.23 kpc. The remaining21 stars lie along the line-of-sight, with some possibly being asdistant as 9 kpc. The dust is found to be distributed in two distinctclouds, one in the local arm at 190 + or - 30 pc and the other in aninterarm cloud of variable extinction at 690 + or - 70 pc.
| UBV-/H-beta/ photometry of luminous stars between L equals 335 deg and L equals 6 deg
Results are reported for photoelectric UBV and H-beta photometry of 316luminous OB stars and early-type supergiants in the region between 335and 6 deg galactic longitude. UBV magnitudes for the 316 stars and betaindexes for 37 of them are presented. Absolute magnitudes, distances,and color excesses are determined for the 161 stars with measured betaindexes or known MK spectral types. The results are discussed in termsof the spiral structure of the Galaxy. From the data obtained forprogram stars assumed to be cluster members, distances are derived forthe open clusters NGC 6167 (1.7 kpc), NGC 6193 (1.3 kpc), Hogg 22 (2.0kpc), NGC 6231 (1.9 kpc), and Tr 27 (1.6 kpc).
| Spectral Types and Radial Velocities of Southern OB+ Stars
Abstract image available at:http://adsabs.harvard.edu/abs/1981A&AS...45..439D
| Southern open star clusters VI. UBV-Hbeta photometry of 18 clusters from Centaurus to Sagittarius.
Abstract image available at:http://adsabs.harvard.edu/abs/1975A&AS...20..155M
| An association of O and B stars in Ara
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963MNRAS.125..105W&db_key=AST
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | סרגל |
| התרוממות ימנית: | 16h34m25.58s |
| סירוב: | -49°38'27.4" |
| גודל גלוי: | 10.797 |
| תנועה נכונה: | 0.6 |
| תנועה נכונה: | -3.6 |
| B-T magnitude: | 11.522 |
| V-T magnitude: | 10.857 |
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INHABITED SKY
