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 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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table7.dat 110 164 Line indices and metal abundances
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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
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Bytes Format Units Label Explanations
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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 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)
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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.
is essentially a measure of the strength of the hydrogen lines.
K and are function of the temperature T, gravity g, and metal
abundance [Fe/H].
MI = (K-K1)/(K2-K1), where
K1=0.3093-1.2815+1.3043H2 and K2=0.6432-2.6043+3.0820H2
Note (3): Notes:
0 = None
1 = Blazhko
2 = Shift
3 = Incomplete
4 = Blend
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Acknowledgements: Raffaele Gratton
(End) Patricia Bauer [CDS] 15-Apr-2004