Late A-type stars: new Strömgren photometric calibrations of absolute magnitudes from HIPPARCOS
Hipparcos trigonometric parallaxes have been used to derive aphotometric absolute magnitude calibration of main-sequence late A-typestars in terms of Strömgren photometric indices - accounting fortemperature, evolution and metallicity effects - and projectedequatorial rotational velocities. The derived calibrations are valid formain-sequence normal A3-A9 and metallic Am stars, showing residuals of0.22 and 0.20 magnitudes, respectively. One of the fitting methods used(BCES) allows the derivation of the observational ZAMS in this spectralrange, showing an excellent accordance with theoretical evolutionarymodels. The evolutionary state of the Am stars is also discussed.Table~A1 is only available in electronic form from CDS via anonymous ftp130.79.128.5, and by e-mail: request to cesca@am.ub.es
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FAUST observations of ultraviolet sources in the direction of Coma
We analyse an ultraviolet observation toward the Coma cluster by meansof the FAUST shuttle-borne telescope. We detect 56 candidate sources toa signal-to-noise ratio of 6.5. Most sources have optical counterpartsin existing catalogues and are stars. 10 sources with no listedcounterparts were observed at the Wise Observatory. We presentidentifications based on low-resolution spectrophotometry, and discussthe foreground stars and the galaxies, all in the foreground of the Comacluster. The FAUST image yields a higher fraction of hot evolved starsthan either of the North Galactic Pole or the Virgo regions, analysedpreviously. We identify these tentatively as cooling white dwarfs in theComa Berenices (Mel111) open cluster.
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On the nature of the AM phenomenon or on a stabilization and the tidal mixing in binaries. I. Orbital periods and rotation.
The paper casts a questioning eye on the unique role of the diffusiveparticle transport mechanism in explaining the Am phenomenon and arguesthat the so-called tidal effects might be of great importance incontrolling diffusion processes. A short period cutoff at =~1.2d as wellas a 180-800d gap were found in the orbital period distribution (OPD) ofAm binaries. The existence of the former can be ascribed to the state ofthe primaries with the almost-filled Roche lobes. The latter couldresult from the combined effects of the diffusion, tidal mixing andstabilization processes. Because the tidal mixing might surpassdiffusion in the binaries with the orbital periods P_orb_ less thanseveral hundred days and might thus sustain the He convection zone,which would otherwise disappear, no Am stars should lie below thisboundary. The fact that they are nevertheless seen there implies theexistence of some stabilization mechanism (as, e.g., that recentlyproposed by Tassoul & Tassoul 1992) for the binaries with orbitalperiods less than 180d. Further evidence is given to the fact that theOPD for the Am and the normal binaries with an A4-F1 primary arecomplementary to each other, from which it stems that Am stars are closeto the main sequence. There are, however, indications that they haveslightly larger radii (2.1-3 Rsun_) than expected for theirspectral type. The generally accepted rotational velocity cutoff at=~100km/s is shown to be of little value when applied on Am binaries ashere it is not a single quantity but, in fact, a function of P_orb_whose shape is strikingly similar to that of the curves of constantmetallicity as ascertained from observations. This also leads to thewell known overlap in rotational velocities of the normal and Am starsfor 402.5d.We have exploited this empirical cutoff function to calibrate thecorresponding turbulent diffusion coefficient associated with tidalmixing, having found out that the computed form of the lines of constantturbulence fits qualitatively the empirical shape of the curves ofconstant metallicity. As for larger orbital periods(20d55km/s found by Burkhart(1979) would then be nothing but a manifestation of insufficientlypopulated corresponding area of larger P_orb_.
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Vilnius Photometry of Stars in the Area of SA 57
Interstellar reddening, as a function of distance in the direction ofthe North Galactic Pole (SA 57), is determined using the two-dimensionalclassification of 63 stars observed in the Vilnius photometric system.The average value of A_V calculated for the stars up to 800 pc distanceis close to zero (the mean value is A_V=0.01 mag) with a standarddeviation of the order of sigma =+/- 0.1 mag. This dispersion of pointsis exactly what is expected from the errors of measurement andclassification.
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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.
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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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The structure of the galactic halo outside the solar circle as traced by the blue horizontal branch stars
A complete sample of blue horizontal branch (BHB) stars in the magnituderange 13.0 less than or equal to V less than or equal to 16.5 isisolated in two Galactic fields that have previously been searched forRR Lyrae variables: SA 57 in the Northern Polar Cap and the LickAstrograph field RR 7 in the Anticenter (l = 183 deg, b = +37 deg).These BHB stars are a subset of the AF stars found in the CaseLow-Dispersion Northern Survey; lists of these AF stars were madeavailable by the late Nick Sanduleak. In the color range 0.00 less thanor equal to (B - V)0 less than or equal to +0.20, we candistinguish the BHB stars among these AF stars by comparing them bothwith well known local field horizontal branch (FHB) stars and also theBHB members of the halo globular clusters M3 and M92. The criteria forthis comparison include (1) a (u - B)K color index (derivedfrom photoelectric observations using the Stroemgren u filter and theJohnson B and V filters) that measures the size of the Balmer jump, (2)a spectrophotometric index lambda that measures the steepness of theBalmer jump, and (3) a parameter D0.2 that is the mean widthof the H-delta and H-gamma Balmer lines measured at 20 percent of thecontinuum level. These criteria give consistent results in separatingBHB stars from higher gravity main sequence AF stars in the color range0.00 less than or equal to (B - V)0 less than or equal to+0.20. All three photometric and spectrophotometric criteria weremeasured for 35 stars in the SA 57 field and 37 stars in the RR 7 fieldthat are in the color range (B - V)0 less than or equal to+0.23 and in the magnitude range 13.0 less than or equal to V less thanor equal to 16.5. For a small number of additional stars only (u -B)K was obtained. Among the AF stars that are fainter than B= 13 and bluer than (B - V)0 = +0.23, about half of those inthe SA 57 field and about one third of those in the lower latitude RR 7field are BHB stars. Isoabundance contours were located empirically inplots of the pseudoequivalent width versus (B - V)0 for thelines of Mg II lambda-4481 A, Ca II lambda-3933 A, and Fe I lambda-4272A. Solar abundances were defined by the data from main sequence stars inthe Pleiades and Coma open clusters. Data from the BHB stars in M3 andM92 defined the (Fe/H) = -1.5 and -2.2 isoabundance contours,respectively. Metallicities of all stars were estimated by interpolatingthe measured pseudoequivalent widths in these diagrams at the observed(B - V)0. The distribution of (Fe/H) found for the BHB starsin this way is very similar to that which we found for the RR Lyraestars in the same fields using the Preston Delta-S method. The spacedensities of these BHB stars were analyzed both separately and togetherwith earlier observations of field BHB stars. This analysis supports atwo-component model for the halo of our Galaxy that is similar in manyrespects to that proposed by Hartwick although our discussion refersonly to the region outside the solar circle.
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A search for wide binaries at the north galactic pole using precise radial velocities
Precise radial velocities are presented from a survey of 247 starscentered on Selected Area 57 at the North Galactic Pole, complete forlate-type stars with V magnitude brighter than 12.0. The radialvelocities have a typical precision of 0.2-0.3 km/s. New spectral typesand distances estimates are presented for 120 of the stars in thesample. All pairs of stars with angular separations between 1 and 600arcsec have been considered, and 11 candidate pairs found with velocitydifferences less than 1.5 km/s. It is estimated that 4 or 5 of the 11candidate pairs are actually bound binaries, but none with separationslarger than 0.1 pc. The constraints imposed by these results on theactual distribution of wide binaries in the Galaxy should now bereanalyzed. The unusual precision of the velocities led to the discoveryof a new cluster associated with the multiple system ADS 8811 ABC.
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Four-color and H-beta photometry near SA 57
Stromgren uvby and H-beta photometry has been obtained for 37 stars inand near the region of SA 57, the Selected Area nearest the northgalactic pole. These stars can serve as secondary standards forphotometric work in this region. Comparisons with previous photometryshows reasonable agreement. The data are analyzed to determineinterstellar reddening, metal abundances of the F-type stars, anddistances. On the average, the stars are somewhat weak lined, comparedto the sun. The reddening is close to zero.
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Lists of photometric AM candidates
The Geneva photometric m parameter (Nicolet and Cramer, 1982) is used inorder to select Am photometric candidates from the Rufener (1981)catalogue. Two lists are given, the first containing field stars and thesecond cluster stars. According to the photometric criteria thediffusion process probably responsible for the Am phenomenon takes placerather quickly as Am candidates are present in young clusters. It isconfirmed that the phenomenon is enhanced by low rotational velocity andhigh metallicity. The age seems to slightly affect the Am phenomenon.
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Further Studies of A-Stars and F-Stars in the Region of the North Galactic Pole - Part Four - a Catalogue of Uvbyr Photometry and Derived Quantities
Not Available
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Further Studies of A-Stars and F-Stars in the Region of the North Galactic Pole - Part Three - a Catalogue of Star Names and Positions
Not Available
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The distribution of stars to V = 16th magnitude near the north galactic pole - Normalization, clustering properties, and counts in various bands
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981ApJ...246..122B&db_key=AST
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Properties of AM stars in the Geneva photometric system
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....92..289H&db_key=AST
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Studies of A and F stars in the region of the North galactic pole-I. Radial velocities and MK Classifications
Not Available
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Multicolor photometry of metallic-line stars. III. A photometric catalogue
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974RMxAA...1..175M&db_key=AST
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Catalogue of AM stars with known spectral types
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS...10..385H&db_key=AST
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UVBY photometry of AM and AP stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78..192W&db_key=AST
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Interstellar reddening near the north galactic pole
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972PASP...84..497F&db_key=AST
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Observations spectrographiques d'etoiles A a spectre particulier et a raies metalliques.
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Catalogue et bibliographie des étoiles A à spectre particulier - Deuxième supplément
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Photoelectric Magnitudes and Colors of Stars Near the North Galactic Pole.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1964ApJ...140..151H&db_key=AST
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Catalogue et bibliographie des étoiles A à spectre particulier
Not Available
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Photographic photometry at the North galactic Pole.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61...80S&db_key=AST
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