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J/A+A/421/937       Metal abundances of LMC RR Lyrae           (Gratton+, 2004)

Metal abundances of RR Lyrae stars in the bar of the Large Magellanic Cloud. Gratton, R.G., Bragaglia, A., Clementini, G., Carretta, E., Di Fabrizio, L., Maio, M., Taribello, E. <Astron. Astrophys. 421, 937 (2004)> =2004A&A...421..937G
ADC_Keywords: Magellanic Clouds ; Stars, variable ; Abundances, [Fe/H] Keywords: stars: abundances - stars: evolution - stars: Population II - galaxies: Magellanic Clouds Abstract: Metallicities ([Fe/H]) from low resolution spectroscopy obtained with the Very Large Telescope (VLT) are presented for 98 RR Lyrae and 3 short period Cepheids in the bar of the Large Magellanic Cloud. Our metal abundances have typical errors of ±0.17dex. The average metallicity of the RR Lyrae stars is [Fe/H]=-1.48±0.03±0.06 on the scale of Harris (1996, Cat. VII/202). The star-to-star scatter (0.29dex) is larger than the observational errors, indicating a real spread in metal abundances. The derived metallicities cover the range -2.12<[Fe/H]←0.27, but there are only a few stars having [Fe/H]>-1. For the ab-type variables we compared our spectroscopic abundances with those obtained from the Fourier decomposition of the light curves. We find good agreement between the two techniques, once the systematic offset of 0.2 dex between the metallicity scales used in the two methods is taken into account. The spectroscopic metallicities were combined with the dereddened apparent magnitudes of the variables to derive the slope of the luminosity-metallicity relation for the LMC RR Lyrae stars: the resulting value is 0.214±0.047mag/dex. Finally, the 3 short period Cepheids have [Fe/H] values in the range -2.0<[Fe/H]←1.5. They are more metal-poor than typical LMC RR Lyrae stars, thus they are more likely to be Anomalous Cepheids rather than the short period Classical Cepheids that are often found in a number of dwarf Irregular galaxies. Description: Line indices and metal abundances for 98 RR Lyrae and 3 short period Cepheids in the bar of the Large Magellanic Cloud measured from low resolution spectra obtained at the ESO VLT1 telescope (FORS). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table7.dat 110 164 Line indices and metal abundances
See also: VII/202 : Globular Clusters in the Milky Way (Harris, 1997) J/AJ/98/2086 : CCD photometry of NGC 2257 RR Lyrae (Walker 1989) J/AJ/105/527 : Photometry of RR Lyr stars in NGC 1835 (Walker 1993) J/AcA/48/113 : OGLE RR Lyrae VI photometry (Udalski, 1998) J/AcA/53/93 : OGLE RR Lyrae in LMC (Soszynski+, 2003) Byte-by-byte Description of file: table7.dat
Bytes Format Units Label Explanations
1- 8 A8 --- Star Star designation 10- 12 A3 --- VType Variable type (1) 14- 19 F6.3 mag Vmag ? Mean apparent V magnitude 21- 26 F6.3 mag V0mag ? Mean dereddened V magnitude 29- 40 F12.4 d HJD Heliocentric Julian day 43- 47 F5.3 0.1nm K K index (2) 50- 54 F5.3 0.1nm Hdelta Hδ index 56- 61 F6.3 0.1nm Hgamma Hγ index 64- 68 F5.3 0.1nm Hbeta Hβ index 71- 75 F5.3 0.1nm <H> Average H index (2) 77- 82 F6.3 --- MI ? Metallicity Index 85- 89 F5.2 [Sun] [Fe/H] Metallicity [Fe/H] from individual observations 91- 95 F5.2 [Sun] e_[Fe/H] Error in [Fe/H] from individual observations 98-102 F5.2 [Sun] [Fe/H]a ? Average [Fe/H] 104-108 F5.2 [Sun] e_[Fe/H]a ? Error in average [Fe/H] 110 I1 --- Note [0/4]? Notes (3)
Note (1): Variable type: ab = ab-type RR Lyrae c = c-type RR Lyrae d = d-type RR Lyrae SPC = short period Cepheid Note (2): Indices: K is a measure of the strength of the Ca II K line. <H> is essentially a measure of the strength of the hydrogen lines. K and <H> are function of the temperature T, gravity g, and metal abundance [Fe/H]. MI = (K-K1)/(K2-K1), where K1=0.3093-1.2815<H>+1.3043H2 and K2=0.6432-2.6043<H>+3.0820H2 Note (3): Notes: 0 = None 1 = Blazhko 2 = Shift 3 = Incomplete 4 = Blend
Acknowledgements: Raffaele Gratton
(End) Patricia Bauer [CDS] 15-Apr-2004
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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