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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
| 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.
| The collapse of dense star clusters to supermassive black holes - The origin of quasars and AGNs
The results of such fully general relativistic calculations of thegravitational collapse of collisionless equilibrium systems as those ofShapiro and Teukolsky (1985) are presently applied to the dynamicalevolution of a dense cluster of neutron stars or stellar mass blackholes, in conjunction with recent Newtonian Fokker-Planck calculationsof the 'gravothermal catastrophe'. The plausible scenario forsupermassive black hole formation thus obtained, via the collapse ofclusters embedded in evolved galactic nuclei, leads to the birth ofsupermassive black holes whose size is consistent with explanations forquasars and active galactic nuclei.
| Concluding observations of loose stellar clusterings in the southern Milky Way
UBV photometry and spectral classification have been performed on 280stars in the Carina-Crux-Centaurus-Norma region, suspected of belongingto poor open clusters or associations. The work is a concluding part ofa large project for detecting and listing of such objects in order toobtain an improved concept about the true frequency of clusterings inthe Milky Way. The result indicates that a majority of the suspectedobjects are members of various types of physical stellar clusterings,occasionally cluster remnants.
| 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
| On the relationship between the apparent magnitudes given in several catalogues and the UBV system.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...15..215O&db_key=AST
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