A spectroscopic study of field BHB star candidates
New spectroscopic observations are presented for a sample of thirty-oneblue horizontal branch (BHB) star candidates that are sufficientlynearby to have reliable proper motions. Comments are given on a furthertwenty-five stars that have previously been suggested as BHB starcandidates but which were not included in our sample. Moderatelyhigh-resolution spectra (lambda /Delta lambda ~ 15 000) of twenty fiveof our program stars were taken with the coudé feed spectrographat Kitt Peak. Twelve of the program stars were also observed with theCAT spectrograph at ESO. Six of these program stars were observed fromboth hemispheres. IUE low-resolution spectra are available for most ofour candidates and were used, in addition to other methods, in thedetermination of their Teff and reddening. A compilation ofthe visual photometry for these stars (including new photometry obtainedat Kitt Peak) is also given. Abundances were obtained from these spectrausing models computed by Castelli with an updated version of the ATLAS9code (Kurucz 1993a). All thirty one candidates are halo stars. Of these,twenty eight are classified as BHB stars because: [(1)]they lie close tothe ZAHB (in a similar position to the BHB stars in globular clusters)in the Teff versus log g plot. For all but one of thesestars, far-UV data were available which were consistent with other data(Strömgren photometry, energy distributions, Hγ profiles) forderiving Teff and log g. [(2)]they have a distribution of kms-1i (<=40 km s-1) that is similar to thatfound for the BHB in globular clusters. Peterson et al. (1995) and Cohen& McCarthy (1997) have shown that the BHB stars in the globularclusters M13 and M92 have a higher km s-1i (<= 40 kms-1) than those in M3 and NGC 288 (<=20 kms-1). The mean deprojected rotational velocity (/line{v}) wascalculated for both the two globular clusters and the nearby BHB starsamples. A comparison of these suggests that both globular cluster kms-1i types are present in our nearby sample. No obvious trendis seen between km s-1i and either (B-V)o or [Fe/H].[(3)]they have -0.99>=[Fe/H]>=-2.95 (mean [Fe/H] -1.67; dispersion0.42 dex), which is similar to that found for field halo RR Lyrae andred HB stars. These local halo field stars appear (on average) to bemore metal-poor than the halo globular clusters. The local sample of redgiant stars given by Chiba & Yoshii (1998) contains a greaterfraction of metal-poor stars than either our halo samples or the haloglobular clusters. The stars in our sample that have a Teffthat exceeds about 8 500 K show the He i (lambda 4471) line with astrength that corresponds to the solar helium abundance. [(4)]they showa similar enhancement of the alpha -elements (< [Mg/Fe]right > =+0.43+/-0.04 and also < [Ti/Fe]right > = +0.44+/-0.02) to thatfound for other halo field stars of similar metallicity. Based onobservations obtained at KPNO, operated by the Association ofUniversities for Research in Astronomy, Inc., under contract with theNational Science Foundation, and the European Southern Observatory,Chile. Tables 4 and 5 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr
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Some Superficially Normal Stars with Stromgren Photometry Similar to that of Field-Horizontal Stars
We obtained spectra with the Kitt Peak coude feed telescope, a 3 k pixellong CCD camera 5 and grating A of some stars whose published Stromgrenphotometry was similar to that of known field horizontal-branch (FHB)A-type stars. Although none of these seven stars are FHB A stars, theyall have surface gravities appropriate to giants and rotationalvelocities greater than that expected for HB stars. HD 48567 was foundto be a binary star. HD 15042 has metal abundances about 0.1 solar.Candidate A-type FHB stars must always be checked by other measures,e.g., ultraviolet spectra, high dispersion spectra and radialvelocities, to confirm their membership in this class.
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Some New Possible Variable Stars II.
Not Available
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A flux-limited sample of Galactic carbon stars
Published observational data (including IRAS observations) for aflux-limited sample of 215 Galactic carbon stars (CSs) selected from the2-micron sky survey of Neugebauer and Leighton (1969) are compiled inextensive tables and graphs and analyzed statistically. The sample isfound to penetrate a volume of radius 1.5 kpc, and the local CS spacedensity and surface density are calculated as log rho0 (per cu kpc) =2.0 + or - 0.4 and log N (per sq kpc) = 1.6 + or - 0.2, respectively.The total Galactic mass-return rate from these CSs is estimated as 0.013solar mass/yr, implying a time scale of 0.1-1 Myr for the CSevolutionary phase and a mass of 1.2-1.6 solar mass for the (probablyF-type) main-seqence progenitors of CSs.
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Classification of 831 two-micron sky survey sources south of +5 degrees.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975AJ.....80.1011H&db_key=AST
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Comparison of a general catalogue of cool carbon stars and the two-micron Sky survey.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79.1287B&db_key=AST
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A list of additionnal variable stars in the two-micron Sky survey.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78..471L&db_key=AST
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The new identifications of the variable stars with the stars from the "Two-Micron Sky Survey - a preliminary catalog" by G. Neugebauer et al. (IRC).
Not Available
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Identification of IRC-objects.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&A....20..317S&db_key=AST
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Photoelectric Observations of Stars near Northern Hemisphere Selected Areas
Not Available
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Carbon Stars at the Galactic Equator in a Zone 4° Wide.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954ApJ...120..129N&db_key=AST
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