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Polarization measurements of Vega-like stars
Optical linear polarization measurements are presented for about 30Vega-like stars. These are then compared with the polarization observedfor normal field stars. A significant fraction of the Vega-like starsare found to show polarization much in excess of that expected to be dueto interstellar matter along the line of sight to the star. The excesspolarization must be intrinsic to the star, caused by circumstellarscattering material that is distributed in a flattened disk. Acorrelation between infrared excess and optical polarization is foundfor the Vega-like stars.
| Discovery of New Candidate Vega-type Systems from IRAS and the 2 Micron All-Sky Survey
We obtained J (1.25 μm), H (1.65 μm), and Ks (2.17μm) photometry from the 2 Micron All-Sky Survey and 12, 25, 60, and100 μm photometry from the IRAS Faint Source Catalog of 2834 fieldstars. We identified in this sample 296 main-sequence (luminosity classIV, IV-V, or V) stars. We searched the sample of main-sequence stars forexcess 12 μm emission with respect to J, H, and Ksphotospheric emission. We discovered eight systems with 12 μm excessemission newly reported here. These excesses are likely to be fromVega-type circumstellar dust, but small-aperture photometry is needed toconfirm their nature. Preliminary models that assume the excesses arecircumstellar show the dust to be located ~1-10 AU from the stars, whereit is heated to ``terrestrial'' temperatures, ~200-500 K. Colder dustmight also exist in the systems but below the IRAS sensitivity limit.The exception is HD 93331 (B9.5 V), previously known for its IRASfar-infrared excess.
| Candidate Main-Sequence Stars with Debris Disks: A New Sample of Vega-like Sources
Vega-like sources are main-sequence stars that exhibit IR fluxes inexcess of expectations for stellar photospheres, most likely due toreradiation of stellar emission intercepted by orbiting dust grains. Wehave identified a large sample of main-sequence stars with possibleexcess IR radiation by cross-correlating the Michigan Catalog ofTwo-dimensional Spectral Types for the HD Stars with the IRAS FaintSource Survey Catalog. Some 60 of these Vega-like sources were not foundduring previous surveys of the IRAS database, the majority of whichemployed the lower sensitivity Point Source Catalog. Here, we providedetails of our search strategy, together with a preliminary examinationof the full sample of Vega-like sources.
| A catalog of far-ultraviolet point sources detected with the fast FAUST Telescope on ATLAS-1
We list the photometric measurements of point sources made by the FarUltraviolet Space Telescope (FAUST) when it flew on the ATLAS-1 spaceshuttle mission. The list contains 4698 Galactic and extragalacticobjects detected in 22 wide-field images of the sky. At the locationssurveyed, this catalog reaches a limiting magnitude approximately afactor of 10 fainter than the previous UV all-sky survey, TDl. Thecatalog limit is approximately 1 x 10-14 ergs A sq cm/s,although it is not complete to this level. We list for each object theposition, FUV flux, the error in flux, and where possible anidentification from catalogs of nearby stars and galaxies. Thesecatalogs include the Michigan HD (MHD) and HD, SAO, the HIPPARCOS InputCatalog, the Position and Proper Motion Catalog, the TD1 Catalog, theMcCook and Sion Catalog of white dwarfs, and the RC3 Catalog ofGalaxies. We identify 2239 FAUST sources with objects in the stellarcatalogs and 172 with galaxies in the RC3 catalog. We estimate thenumber of sources with incorrect identifications to be less than 2%.
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Наблюдательные данные и астрометрия
| Созвездие: | Гидра |
| Прямое восхождение: | 10h46m24.83s |
| Склонение: | -13°27'35.5" |
| Видимая звёздная величина: | 7.255 |
| Расстояние: | 151.515 парсек |
| Собственное движение RA: | -35.3 |
| Собственное движение Dec: | 1.4 |
| B-T magnitude: | 7.291 |
| V-T magnitude: | 7.258 |
Каталоги и обозначения:
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