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Spectroscopic confirmation of a white dwarf companion to the B star 16 Dra
Using an Extreme Ultraviolet Explorer (EUVE) spectrum, we confirm theidentification of a white dwarf companion to the B9.5V star 16 Dra(HD150100), and constrain its surface temperature to lie between 29,000K and 35,000 K. This is the third B star + white dwarf non-interactingSirius-type binary to be confirmed, after y Pup (HR2875, HD59635) andtheta Hya (HR3665, HD79469). 16 Dra and its white dwarf companion aremembers of a larger resolved proper motion system including the B9V star17 Dra A (HD150117). The white dwarf must have evolved from a progenitormore massive than this star, M_MS~3.7M_sun. White dwarf companions to Bstars are important since they set an observational limit on the maximummass for white dwarf progenitors, and can potentially be used toinvestigate the high mass ends of the initial-final mass relation andthe white dwarf mass-radius relation.
| BVR Photometry of Northern Hemisphere Luminous Stars. III. LS and HD Stars
CCD-based BVR photometry of 48 previously unobserved stars drawn fromvolumes V and VI of the Luminous Stars in the Northern Milky Way,Luminous Stars in the Southern Milky Way, and HD catalogs is reported.
| 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.
| The ROSAT Wide Field Camera all-sky survey of extreme-ultraviolet sources - II. The 2RE Source Catalogue
During 1990-1991 the Wide Field Camera (WFC) on the ROSAT satelliteperformed the first all-sky survey at EUV wavelengths. The survey wasconducted in two `colours' using broad-band filters to define wavebandscovering the ranges 60-140 A and 112-200 A. It was fully imaging, witheffective spatial resolution of about 3 arcmin FWHM, and point sourcelocation accuracy of typically better than 1 arcmin. From an initialanalysis, Pounds et al. published the WFC Bright Source Catalogue (BSC)of 383 sources. In this paper we report results from reprocessing of thecomplete survey database; the resulting list of sources is the `2RE'Catalogue. It contains 479 sources, of which 387 are detected in bothsurvey wavebands, a significant advance on the BSC (80 per cent versus60 per cent). Improvements over the original BSC include: (i) betterrejection of poor aspect periods, and smaller random errors in theaspect reconstruction; (ii) improved background screening; (iii)improved methods for source detection; (iv) inclusion of atime-variability test for each source; (v) more extensive investigationof the survey sensitivity. We define the catalogue selection criteria,and present the catalogue contents in terms of tables and sky maps. Wealso discuss the sky coverage, source number-flux relations, opticalidentifications and source variability.
| Four-colour and H-beta photometry of blue stars selected from a balloon-ultraviolet survey and other sources
New uvby and/or H-beta photometry is obtained at the Chiranhigh-altitude outstation for 105 stars. Certain of the program stars areselected from a comparison of the SCAP 2000 balloon-ultraviolet skysurvey of the Laboratoire d'Astronomie Spatiale with the correspondingblue and red prints of the Palomar Observatory sky survey. Only a smallportion of these stars turn out to be B stars, whereas, the rest of thestars, which are selected from a variety of other sources, are mostly Bstars and if of normal luminosity are in many cases many Population Iscale heights from the galactic plane. It is shown that theidentification of B stars is practicable only at a good observing siteand that if H-beta photometry is also obtained, sdOB, sdB, and hothorizontal branch B stars can be distinguished from normal stars bytheir position in the beta/c(0) diagram.
| Four-colour photometry of B stars north of B = + 45 deg and comparison with the south
Four-color photometry of 33 Henry Draper B stars north of b = + 45 degis presented. Most are little-reddened B or intermediate-A stars. A newAm star is discovered. The new measures essentially complete uvbyphotometry of all HD B stars within 45 deg of either galactic pole. Thenorthern and southern cones of HD B stars are compared, and selectioneffects deduced. Far from the galactic plane, it appears that B starsmay be equally distributed north and south of the plane; closer to thesun, an asymmetry associated with Gould's Belt is evident.
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| Takýmyýldýz: | Buyuk Ayi |
| Sað Açýklýk: | 10h51m05.91s |
| Yükselim: | +56°14'15.8" |
| Görünürdeki Parlaklýk: | 7.453 |
| Uzaklýk: | 137.931 parsek |
| özdevim Sað Açýklýk: | -27.4 |
| özdevim Yükselim: | -24.8 |
| B-T magnitude: | 7.503 |
| V-T magnitude: | 7.458 |
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