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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.
| 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.
| NGC 6204 and HOGG 22: The Odd Couple
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111.1609F&db_key=AST
| The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| Analysis of the results of MK classification of 176 stars in 37 southern open clusters
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979A&AS...37..345F&db_key=AST
| Southern open stars clusters. III. UBV-Hbeta photometry of 28 clusters between galactic longitudes 297d and 353d
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS...10..135M&db_key=AST
| 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: | מזבח |
| התרוממות ימנית: | 16h46m00.66s |
| סירוב: | -47°01'19.6" |
| גודל גלוי: | 9.778 |
| תנועה נכונה: | -3.3 |
| תנועה נכונה: | -3.8 |
| B-T magnitude: | 9.993 |
| V-T magnitude: | 9.796 |
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