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Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| X-ray studies of coeval star samples. III - X-ray emission in the Ursa Major stream
Results are reported from a comprehensive survey of X-ray emission fromstars known or suspected to be members of the UMa cluster and/or stream.Of the 42 UMa member stars surveyed, 18 were detected as X-ray sources,and spectral analysis was performed for 10 stars with sufficient X-raycounts. Consideration is given to relations between X-ray luminosity,color, and kinematics of the sample stars, and the X-ray spectra of theUMa stars are discussed in the context of the general problem of stellarX-ray temperatures. Also confirmed is the lack of X-ray-emitting Adwarfs among UMa members; among stars of later spectra type there is arather large dispersion in X-ray luminosity. This dispersion cannotreadily be explained by contamination with field star interlopers andappears rather to be a property of the UMa X-ray luminosity distributionfunction.
| UBV photoelectric catalogue (1986). II - Analysis
The UBV photoelectric data of the stars presenting several entries inthe 1986 edition of the UBV catalog have been systematicallyintercompared, and this paper presents a discussion of the stars forwhich discrepancies larger than 0.2 mag were found. Thirty-six probablyvariable stars have been detected, among which 18 are Be stars. Sixtyfurther stars present differences in the V magnitude larger than 0.2mag. Sixteen stars already appear in the NSV catalog. Although manyproblems are probably due to poor observations, new (eclipsing) variablestars may be found in this sample. Complete disagreement is foundbetween the values published from two independent sources in 34 cases. Afirst analysis of the quality of the UBV data shows that 65 percent ofthe differences in the V magnitude and in U-B color, for respectively11,500 and 7200 stars with two sources of data, are smaller than 0.04.The scatter on the B-V index appears to be smaller, since the samepercentage reaches 79 percent.
| UBV Photoelectric Photometry Catalogue (1986). III Errors and Problems on DM and HD Stars
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| Spectral types in the Ursa major stream.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978PASP...90..429L&db_key=AST
| Three-Color Photometry of Nearby Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1957ApJ...126..113J&db_key=AST
| The color-luminosity diagram of the UMa group.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954AJ.....59..233M&db_key=AST
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Membro dei seguenti gruppi:
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Osservazione e dati astrometrici
| Costellazione: | Orsa Maggiore |
| Ascensione retta: | 12h55m37.14s |
| Declinazione: | +57°06'24.0" |
| Magnitudine apparente: | 9.218 |
| Moto proprio RA: | 116.7 |
| Moto proprio Dec: | -29 |
| B-T magnitude: | 10.087 |
| V-T magnitude: | 9.29 |
Cataloghi e designazioni:
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