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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.
| An extensive Delta a-photometric survey of southern B and A type bright stars
Photoelectric photometry of 803 southern BS objects in the Deltaa-system as detection tool for magnetic chemically peculiar (=CP2) starshas been carried out and compared to published spectral types. Thestatistical yield of such objects detected by both techniques ispractically the same. We show that there are several factors whichcontaminate the search for these stars, but this contamination is onlyof the order of 10% in both techniques. We find a smooth transition fromnormal to peculiar stars. Our sample exhibits the largest fraction ofCP2 stars at their bluest colour interval, i.e. 10% of all stars in thecolour range -0.19 <= B-V < -0.10 or -0.10 <= b-y < -0.05.No peculiar stars based on the Delta a-criterion were found at bluercolours. Towards the red side the fraction of CP2 stars drops to about3% for positive values of B-V or b-y with red limits roughlycorresponding to normal stars of spectral type A5. The photometricbehaviour of other peculiar stars: Am, HgMn, delta Del, lambda Boo, Heabnormal stars, as well as Be/shell stars and supergiants shows someslight, but definite deviations from normal stars. Spectroscopic andvisual binaries are not distinguished from normal stars in their Delta abehaviour. The results of this work justify larger statistical work(e.g. in open clusters) employing more time-saving photometric methods(CCD). \newpage Based on observations obtained at the European SouthernObservatory, La Silla, Chile. This research has made use of the Simbaddatabase, operated at CDS, Strasbourg, France. Table 2 is only availablein electronic form via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| Good Abundances from Bad Spectra: II. Application and a New Stellar Color-Temperature Calibration
Stellar spectra derived from current multiple-object fiber-fedspectroscopic radial-velocity surveys, of the type feasible with, amongother examples, AUTOFIB, 2dF, HYDRA, NESSIE, and the Sloan survey,differ significantly from those traditionally used for determination ofstellar abundances. The spectra tend to be of moderate resolution(around 1 A) and signal-to-noise ratio (around 10-20 per resolutionelement), and cannot usually have reliable continuum shapes determinedover wavelength ranges in excess of a few tens of Angstroms.Nonetheless, with care and a calibration of stellar effectivetemperature from photometry, independent of the spectroscopy, reliableiron abundances can be derived. We have developed techniques to extracttrue iron abundances and surface gravities from low signal-to-noiseratio, intermediate resolution spectra of G-type stars in the 4000-5000Awavelength region. The theoretical basis and calibration using syntheticspectra are described in detail in another paper (Jones, Gilmore andWyse, 1995). The practical application of these techniques toobservational data, which requires some modification from the ideal caseof synthetic data, is given in the present paper. An externally-derivedestimate of stellar effective temperature is required in order toconstrain parameter space sufficiently; a new derivation of the V-Ieffective temperature relation is thus an integral part of the analysispresented here. We have derived this relationship from analysis ofavailable relevant data for metal-poor G dwarfs, the first suchcalibration. We test and calibrate our techniques by analysis of spectraof the twilight sky, of member stars of the cluster M67, and of a set offield stars of known metallicity. We show that this method, combinedwith our new color-temperature calibration, can provide true ironabundances, with an uncertainty of less than 0.2 dex over the range ofmetallicty found in the Galactic thick and thin disks, from spectraobtained with fiber-fed spectrographs. (SECTION: Stars)
| 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%.
| Measures of Southern Double Stars in 1981
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982A&AS...50..115W&db_key=AST
| Polarization measurements of 313 nearby stars
The linear polarization of 313 low galactic latitude stars has beenmeasured. With few exceptions all program stars have a spectral typelater than B9 and are within 600 parsec of the sun. 181 stars aresituated at the southern sky and 132 at the northern sky.
| Visual double stars measured at Las Campanas Observatory, Chile.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975PASP...87..945H&db_key=AST
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | שדרית |
| התרוממות ימנית: | 08h39m13.20s |
| סירוב: | -60°19'02.0" |
| גודל גלוי: | 6.36 |
| מרחק: | 134.048 פארסק |
| תנועה נכונה: | -31 |
| תנועה נכונה: | 27.6 |
| B-T magnitude: | 6.714 |
| V-T magnitude: | 6.756 |
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