CDROM/AJ/V108/P1016 Local RR Lyrae Stars (Layden 1994) ================================================================================ The Metallicities and Kinematics of RR Lyrae Variables. I. New Observations of Local Stars Andrew C. Layden <1994, AJ, 108, 1016> =1994AJ....108.1016L ================================================================================ Abstract: In order to study the structure and formation history of the galaxy, we have obtained low-to-moderate dispersion spectra of 302 nearby RR Lyrae variables of Bailey type "ab." We derived abundances, typically accurate to 0.15-0.20 dex and calibrated to the Zinn & West [ApJS, 55, 45 (1984)] globular cluster metallicity scale, from the pseudo- equivalent widths of the Ca II K, Hdelta, Hgamma, and Hbeta lines. Radial velocities accurate to between 2 and 30 km/s were obtained from the spectra and from the literature. Distances accurate to between 5% and 20% were derived from published apparent magnitudes and Burstein & Heiles [AJ, 87, 1165 (1982)] reddenings. The metallicity distribution of the RR Lyrae stars peaks at [Fe/H]_K approx. -1.5, and is narrower than that of the Ryan & Norris [AJ, 101, 1865 (1991)] subdwarfs, as expected since the most metal-rich and metal-poor progenitors preferentially appear as stable red and blue horizontal branch stars, rather than as RR Lyrae. The metal-rich tail of the RR Lyrae distribution extends to [Fe/H]_K approx. 0, and a qualitative analysis of the distribution of distances from the galactic plane shows that the stars in this tail (i.e., [Fe/H]_K > -1.0) are more concentrated to the plane than the more metal-poor stars. The abundance distribution of the local RR Lyrae stars is in excellent agreement with the changing abundance distributions of distant RR Lyrae stars as a function of galactocentric distance, as derived by Suntzeff et al. [ApJ, 367, 528 (1991)], who ascribed this change to systematic variations in horizontal branch morphology (probably age variations) with galactocentric distance. The abundance distribution of the local RR Lyrae stars also agrees well with those of the distant RR Lyrae stars as a function of distance from the galactic plane. There is no evidence for an abundance gradient in this direction, suggesting that gaseous dissipation did not play a major role in the formation of the outer halo. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table9.dat 79 302 New data for local RR Lyrae variables -------------------------------------------------------------------------------- Byte-by-byte Description of file: table9.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 A8 --- Name Variable star name (as in GCVS4) 9-14 F6.2 --- Fe_H Metal abundance, on Zinn & West (1984) scale 15 A1 --- u_Fe_H ':' indicates particularly uncertain [Fe/H] 16-20 F5.2 --- e_Fe_H Estimated error in [Fe/H] 21-22 I2 --- N_K Number of spectra used for [Fe/H] estimate 23-28 F6.2 mag Intensity-averaged V magnitude 29 A1 --- r_ *Reference for 30 1X --- --- Blank 31 A1 --- pb *Photometric passband 32-36 F5.2 --- A_V *Interstellar absorption in V 37-41 F5.2 kpc Dist Distance from Sun 42-46 F5.2 kpc e_Dist Estimated error in distance 47-52 F6.2 kpc Z Distance from Galactic plane 53-58 F6.2 kpc R_gc Dist. from Galactic center, assumes Ro=8kpc 59-63 I5 km/s V_rad Systemic radial velocity 64-66 I3 km/s e_V_rad Estimated error in measured radial velocity 67-68 I2 --- N_V Number of spectra used in V_rad estimate 69-70 I2 --- cm *Radial velocity combination method 71-75 I5 km/s V_sys *Final systemic radial velocity 76-78 I3 km/s e_V_sys Estimated error in V_sys 79 A1 --- u_V_sys *':' indicates disagreement in velocity -------------------------------------------------------------------------------- Notes for file: table1.dat -------------------------------------------------------------------------------- r_: Intensity-averaged V magnitude reference: a = value from Schmidt 1991, AJ, 102, 1766 b = Layden (1994) photoelectric photometry c = Layden (1994) recalibration of photographic photometry d = Photometry from Nikolev et al. 1984, The Mean Light and Colour (B-V and U-B) Curves of 210 Field RR Lyrae Types Stars, (University of Sofia, Sofia) e = GCVS4 photometry uncertain pb: Photometry passband: V = photoelectric V; B = photoelectric B; p = photographic; v = (photo)visual A_V: Interstellar absorption in V, from Burstein & Heiles 1982, AJ, 187, 1165 cm: Radial velocity combination method: 1 = fits with standard RV curve; 2 = weighted mean; 3 = single observation only V_sys: Final systemic radial velocity, a combination of V_rad and values from the literature u_V_sys: A colon, ':', indicates the measured and literature velocity estimates disagree by more than the quoted error; the quoted error may be too small. -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 31-Oct-1994