Reddening and the Extinction Law at High Galactic Latitude
We present near-infrared (JHKL) photometry of 103 southern stars locatedbehind translucent interstellar clouds at high Galactic latitude. Ourdata are combined with visual photometry and spectral type informationfrom the literature in a detailed analysis of the wavelength dependenceof interstellar extinction by dust in these high-latitude clouds. Weinvestigate the shape of the near-infrared extinction curve and evaluatethe total line-of-sight extinction (AV) and ratio oftotal-to-selective extinction (RV) in each line of sight.Sources of uncertainty in RV arising from photometric errorsand spectral classification errors are carefully assessed and quantifiedas functions of the line-of-sight reddening. We detect appreciabledifferences in our results compared with the average extinction curvefor dust in the diffuse interstellar medium (ISM) close to the Galacticplane. Assuming a power-law form in the near-infrared, we find the meanfor high-latitude clouds to be well described by~λ-2.3, somewhat steeperthan that for the diffuse ISM(~λ-1.8). Our sampleincludes a substantial number of lines of sight with low RVvalues (47% with RV<2.8) relative to the diffuse ISMaverage of 3.05+/-0.15. We conclude that many high-latitude clouds haveenhanced abundances of relatively small grains.
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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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Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
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UBVRI photometry of the FK5 Extension Catalogue Stars
UBVRI photometry in the Kron-Cousins system for 272 stars of theExtension Catalogue of the Fifth Fundamental Star Catalogue (FK5 stars)in the declination zone +7 deg to -90 deg is presented. Tables 1-2 arealso available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html Based on observations made atthe European Southern Observatory, La Silla, Chile.
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The Fundamental Parameters of Field Horizontal-Branch Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2291G&db_key=AST
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Spectral Characteristics of Field Horizontal-Branch Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2286C&db_key=AST
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Heisse Horizontalaststerne im Feld der Milchstrasse und in Kugelsternhaufen.
Not Available
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Photometric and spectroscopic analysis of high galactic latitude molecular clouds. II - High-resolution spectroscopic observations of NA I, CA II, CA I, CH, and CH(+1)
High-resolution spectroscopic observations in the wavelengths of thespecies Na I, Ca II, and Ca I and the molecular species CH and CH(+)have been performed toward stars behind a variety of high galacticlatitude molecular clouds (HLCs). Seventeen new detections of molecularabsorption are reported. The sizes, densities, and molecular contentfound for the HLCs are consistent with an interpretation of HLCmolecular cores as extremely compact structures of enhanced molecularcontent which may have evolved from larger H I shells.
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On the identification of field horizontal-branch A stars
Field horizontal-branch A-star candidates are found by spectroscopic andcolorimetric surveys. To confirm their status four-color, H-betaphotometry and ultraviolet spectrophotometry have been employed. In thispaper, the importance of high-dispersion spectroscopy to identifynonclass members by inspection is demonstrated. The final confirmationof class membership requires an elemental abundance analysis.
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Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental stars
The mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed.
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Horizontal-branch A stars. II - The temperature scale and a discussion of the surface gravities
Effective temperatures and surface gravities have been derived for fieldand globular-cluster horizontal-branch A stars. The values are obtainedby fitting spectrum scans to the energy distributions calculated byATLAS model atmospheres (Kurucz, 1979, 1981). The validity and accuracyof the results are discussed.
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Ultraviolet spectra of field horizontal-branch A-type stars
The spectra of four FHB stars have been obtained at about 5-A resolutionbetween 1200 and 1900 A with the IUE. The intensity distributions ofthree of the stars match that of the 'FHB distribution' in Huenemoerderet al. (1984). The coolest star of the four, HD 2857, has UVdistribution that drops off rapidly short of 1750 A.
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Faint secondary standards for spectrophotometry and the energy distributions of horizontal-branch A-stars
Not Available
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Finding charts for field horizontal-branch A-type stars.
Not Available
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Field horizontal-branch stars at ultraviolet and visual wavelengths
The spectra of 17 field horizontal-branch (FHB) stars observed at about5-A resolution between 1150 and 3200 A with the IUE and about 8-Aresolution between 3600 and 5800 A with the Reticon of Pine BlufObservatory are compared with data of Population I stars of similartemperatures and with theoretical model atmospheres. The FHB stars haveweaker spectral lines and are brighter than Population I stars atwavelengths below 1800 A. The models are too bright below 1600 A toproperly match the Population II star energy distributions. Temperaturesfor the FHB stars which are consistent for the wavelength range observedare obtained.
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Scanner observations of field horizontal-branch A stars
Measurements have been conducted regarding the energy distributions of16 field horizontal-branch A stars, plus nine others of miscellaneoustypes, at 20 wavelengths between 3450 and 6970 A using the HCO scannerson 0.9 m telescopes at Kitt Peak and Cerro Tololo Observatories. Theobservations are reported here as absolute energy distributions on thesystem of Hayes and Latham. The (internal) measurement error (std. dev.)is 0.025 mag per observation, averaged over all wavelengths.
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Astrophysical Parameters from Four-Colour Photometry
Not Available
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Gravities of Blue Horizontal-Branch Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972ApJ...171L..51P&db_key=AST
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Possible horizontal-branch stars at high galactic latitudes. III.
Abstract image available at:http://adsabs.harvard.edu/abs/1969AJ.....74..209P
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