Browsing by Subject "stars: variables: rr"
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Item The Absolute Magnitude Of RRc Variables From Statistical Parallax(2013-09) Kollmeier, Juna A.; Szczygiel, Dorota M.; Burns, Christopher R.; Gould, Andrew; Thompson, Ian B.; Preston, George W.; Sneden, Christopher; Crane, Jeffrey D.; Dong, Subo; Madore, Barry F.; Morrell, Nidia; Prieto, Jose L.; Shectman, Stephen; Simon, Joshua D.; Villanueva, Edward; Sneden, ChristopherWe present the first definitive measurement of the absolute magnitude of RR Lyrae c-type variable stars (RRc) determined purely from statistical parallax. We use a sample of 242 RRc variables selected from the All Sky Automated Survey for which high-quality light curves, photometry, and proper motions are available. We obtain high-resolution echelle spectra for these objects to determine radial velocities and abundances as part of the Carnegie RR Lyrae Survey. We find that M-V,M-RRc = 0.59 +/- 0.10 at a mean metallicity of [Fe/H] = -1.59. This is to be compared with previous estimates for RRab stars (M-V,M-RRab = 0.76 +/- 0.12) and the only direct measurement of an RRc absolutemagnitude (RZ Cephei, M-V,M-RRc = 0.27 +/- 0.17). We find the bulk velocity of the halo relative to the Sun to be (W-pi, W-theta, W-z) = (12.0,-209.9, 3.0) km s(-1) in the radial, rotational, and vertical directions with dispersions (sigma(W pi), sigma(W theta), sigma(Wz)) = (150.4, 106.1, 96.0) km s(-1). For the disk, we find (W-pi, W-theta, W-z) = (13.0,-42.0,-27.3) km s(-1) relative to the Sun with dispersions (sigma(W pi), sigma(W theta), sigma(Wz)) = (67.7, 59.2, 54.9) km s(-1). Finally, as a byproduct of our statistical framework, we are able to demonstrate that UCAC2 proper-motion errors are significantly overestimated as verified by UCAC4.Item Radial Velocities and Pulsation Ephemerides of 11 Field RR Lyrae Stars(2011-06) For, Bi-Qing; Preston, George W.; Sneden, Christopher; For, Bi-Qing; Sneden, ChristopherWe present new radial velocities (RVs), improved pulsation periods, and reference epochs of 11 field RR Lyrae ab-type variables: AS Vir, BS Aps, CD Vel, DT Hya, RV Oct, TY Gru, UV Oct, V1645 Sgr, WY Ant, XZ Aps, and Z Mic. This study is based on high-resolution spectra obtained with the echelle spectrograph of the 2.5 m du Pont telescope at Las Campanas Observatory. We obtained similar to 200 spectra per star (i.e., a total of similar to 2300 spectra), distributed more or less uniformly throughout their pulsation cycles. RV curves and photometric light curves phased to our new ephemerides are presented for all program stars. In a subsequent paper, we will use these spectra to derive stellar atmospheric parameters and chemical compositions throughout the pulsational cycles, based purely on spectroscopic constraints.