J/ApJ/682/1029 Abundances in OGLE-2007-BLG-349S (Cohen+, 2008)
Clues to the metallicity distribution in the galactic bulge: abundances in
OGLE-2007-BLG-349S.
Cohen J.G., Huang W., Udalski A., Gould A., Johnson J.A.
<Astrophys. J., 682, 1029-1040 (2008)>
=2008ApJ...682.1029C 2008ApJ...682.1029C
ADC_Keywords: Abundances ; Equivalent widths ; Gravitational lensing ;
Stars, dwarfs
Keywords: galaxies: bulges - Galaxy: bulge - gravitational lensing -
stars: abundances
Abstract:
We present an abundance analysis based on high-dispersion and high
signal-to-noise ratio Keck spectra of a very highly microlensed
Galactic bulge dwarf, OGLE-2007-BLG-349S, with Teff∼5400K. The
amplification at the time the spectra were taken ranged from 350 to
450. This bulge star is highly enhanced in metallicity with
[Fe/H]=+0.51±0.09dex. The abundance ratios for the 28 species of 26
elements for which features could be detected in the spectra are
almost all solar. In particular, there is no evidence for enhancement
of any of the α-elements, including O and Mg. We conclude that
the high [Fe/H] seen in this star, when combined with the equally high
[Fe/H] derived in previous detailed abundance analysis of two other
Galactic bulge dwarfs, both also highly magnified by microlensing,
implies that the median metallicity in the Galactic bulge is very
high. We thus infer that many previous estimates of the metallicity
distribution in the Galactic bulge have substantially underestimated
the mean Fe metallicity there due to sample bias, and suggest a
candidate mechanism for such. If our conjecture proves valid, it may
be necessary to update the calibrations for the algorithms used by
many groups to interpret spectra and broadband photometry of the
integrated light of very metal-rich old stellar populations, including
luminous elliptical galaxies.
Description:
We took three consecutive spectra, each 1350s in length with the
HIRES-R on the Keck I telescope in the night of 2007 September 5.
Objects:
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RA (2000) DE Designation(s)
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18 05 24.4 -26 25 19 EWS 2007-BLG-349 = MOA 2007-BLG-379
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 38 249 Equivalent widths for OGLE-2007-BLG-349S
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See also:
J/A+A/512/A41 : Abundances of microlensed stars in the Bulge (Bensby+, 2010)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm lambda Wavelength (Å)
9- 13 A5 --- Ion Species identification
15- 18 F4.2 eV ExPot Excitation potential
20- 25 F6.3 [-] log(gf) Log of the oscillator strength
27 A1 --- n_log(gf) [a] inverted solar analysis used
to determine gf
29- 30 A2 --- l_EW [≤ ] Limit flag on EqWid
32- 36 F5.1 10-13m EW ? Equivalent width in milli-Angstroms
38 A1 --- n_EW [s] Synthesis used to derive EqWid
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 24-Nov-2010