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Description
This catalog presents metal abundance, distance and radial velocity data on a sample of 302 ab-type RR Lyrae variables within about 2.5 kpc of the Sun. The metal abundance information was obtained from low-medium resolution spectra, using the pseudo-equivalent widths of the Ca II K line and the the H-delta, H-gamma and H-beta lines. The technique employed was similar to Preston's (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1959ApJ...130..507P%201959ApJ...130..507P">1959ApJ...130..507P 1959ApJ...130..507P</A>) Δ-S method, though significant differences exist; see the source reference for details. The data were calibrated to the Zinn & West (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1984ApJS...55...45Z%201984ApJS...55...45Z">1984ApJS...55...45Z 1984ApJS...55...45Z</A>) globular cluster abundance scale. The photometry employed in the distance determinations was primarily taken from the General Catalog of Variable Stars (1985, hereafter GCVS4). Exceptions are noted in column 29; the letters match the footnotes in Table 10 of Layden (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1994AJ....108.1016L%201994AJ....108.1016L">1994AJ....108.1016L 1994AJ....108.1016L</A>). The minimum and maximum light photometry, and rise-time were combined following Barnes & Hawley (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1986ApJ...307L...9B%201986ApJ...307L...9B">1986ApJ...307L...9B 1986ApJ...307L...9B</A>) to give an estimate of the intensity- averaged magnitude, i.e. the magnitude the star would have if it were not variable. When the GCVS4 quoted magnitudes in passbands other than V, the GCVS4 magnitudes were transformed to the V passband using the relations established in Layden (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1994AJ....108.1016L%201994AJ....108.1016L">1994AJ....108.1016L 1994AJ....108.1016L</A>). The interstellar absorption estimates are from Burstein & Heiles (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1982AJ.....87.1165B%201982AJ.....87.1165B">1982AJ.....87.1165B 1982AJ.....87.1165B</A>), modified by a simple dust-distribution model. The distances were computed assuming the Mv(RR)-[Fe/H] relation of Carney, Storm & Jones (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1992ApJ...386..663C%201992ApJ...386..663C">1992ApJ...386..663C 1992ApJ...386..663C</A>). Radial velocities were measured from the spectra via cross-correlation with secondary velocity standards. The velocities from the individual spectra were fit with a standard radial velocity curve in the (phase, velocity) plane, to give an estimate of the systemic (center of mass) velocity of each star. The error in this value was estimated from the scatter about the best-fit velocity curve, and the quality of the spectra employed. Other methods were used to combine the individual velocities when the situation demanded (cm = 2,3 in column 70; see Layden (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1994AJ....108.1016L%201994AJ....108.1016L">1994AJ....108.1016L 1994AJ....108.1016L</A>) for details). The observed velocities were combined with values from the literature to produce a final, best estimate of the systemic radial velocity of each star, and its error.
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