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מאמרים קשורים
Searching for links between magnetic fields and stellar evolution. I. A survey of magnetic fields in open cluster A- and B-type stars with FORS1
Context: .About 5% of upper main sequence stars are permeated by astrong magnetic field, the origin of which is still matter of debate. Aims: . With this work we provide observational material to studyhow magnetic fields change with the evolution of stars on the mainsequence, and to constrain theory explaining the presence of magneticfields in A and B-type stars. Methods: . Using FORS1 inspectropolarimetric mode at the ESO VLT, we have carried out a survey ofmagnetic fields in early-type stars belonging to open clusters andassociations of various ages. Results: . We have measured themagnetic field of 235 early-type stars with a typical uncertainty of 100 G. In our sample, 97 stars are Ap or Bp stars. For thesetargets, the median error bar of our field measurements was 80 G.A field has been detected in about 41 of these stars, 37 of which werenot previously known as magnetic stars. For the 138 normal A and B-typestars, the median error bar was 136 G, and no field was detected in anyof them.
| 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
| Membership, fundamental parameters and luminosity function of the open cluster NGC 5662
New photoelectric UBV photometry of 237 stars brighter than V = 14.0 aswell as DDO and Washington photometry of three red stars in the opencluster NGC 5662 are presented. Nearly one-third of the stars sampledare found to be members of the cluster based on photometric andastrometric indicators. NGC 5662 contains two red giants and twophotometric variable stars. The reddening across the cluster is found tobe variable, the mean value being E(B-V) = 0.31 + or - 0.04. A distanceof (790 + or - 55) pc, an age of 7.9 x 10 to the 7th yr, a metalabundance of Fe/H = - 0.03 + or - 0.13 relative to the sun, and otherfundamental parameters are also derived. On the basis of the improvedcluster parameters derived here, it is concluded that the 5.5 d CepheidV Cen is almost certainly a member of NGC 5662.
| Photoelectric search for CP2-stars in open clusters. XI - NGC 3532 and NGC 5662
Delta-a photometry was carried out for 164 stars in NGC 3532 (the mostpopulous cluster studied so far in this series) and 27 stars in NGC5662. Surprisingly, only one mildly peculiar star (Koelbloed 232) wasidentified this way among the roughly hundred cluster members of NGC3532. Three photometrically peculiar objects were found among theapproximately 60 field stars in the cluster area. This is about theaverage frequency of CP2-stars, in contrast to the pronounced shortageof CP2-stars in the rather old cluster NGC 3532. In NGC 5662 twoCP2-objects, MV6 and MV10, were identified. MV6, however, is a probablenonmember based on its proper motion data. As in some previous casesagain a negative Delta-a object was found with reportedBe-characteristics (NGC 5662-MV29).
| 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
| Photoelectric and photographic photometry in the open clusters NGC 5617, TR 22 and NGC 5662.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...34..417H&db_key=AST
| A spectral survey of the southern Milky Way 1 : general description and catalogue 1 (l=306 -318 degrees).
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...16..445S&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
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | קנטאור |
| התרוממות ימנית: | 14h36m01.24s |
| סירוב: | -56°31'04.3" |
| גודל גלוי: | 8.839 |
| מרחק: | 10000000 פארסק |
| תנועה נכונה: | -3.2 |
| תנועה נכונה: | -6.4 |
| B-T magnitude: | 8.952 |
| V-T magnitude: | 8.849 |
קטלוגים וכינוים:
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