J/ApJ/699/66 Abundances in two Galactic bulge stars (Cohen+, 2009)
Clues to the metallicity distribution in the Galactic bulge: abundances
in MOA-2008-BLG-310S and MOA-2008-BLG-311S.
Cohen J.G., Thompson I.B., Sumi T., Bond I., Gould A., Johnson J.A.,
Huang W., Burley G.
<Astrophys. J., 699, 66-75 (2009)>
=2009ApJ...699...66C 2009ApJ...699...66C
ADC_Keywords: Abundances ; Equivalent widths ; Gravitational lensing ;
Stars, dwarfs
Keywords: Galaxy: bulge - gravitational lensing - stars: abundances
Abstract:
We present abundance analyses based on high dispersion and high
signal-to-noise ratio Magellan spectra of two highly microlensed
Galactic bulge stars in the region of the main-sequence turnoff
with Teff∼5650K. We find that MOA-2008-BLG-310S has
[Fe/H]8=+0.41±0.09dex and MOA-2008-BLG-311S has +0.26±0.09dex.
The abundance ratios for the ∼20 elements for which features could be
detected in the spectra of each of the two stars follow the trends
with [Fe/H] found among samples of bulge giants. Combining these two
bulge dwarfs with the results from previous abundance analysis of four
other Galactic bulge turnoff region stars, all highly magnified by
microlensing, gives a mean [Fe/H] of +0.29dex. This implies that there
is an inconsistency between the Fe-metallicity distribution of the
microlensed bulge dwarfs and that derived by the many previous
estimates based on surveys of cool, luminous bulge giants, which have
mean [Fe/H]~-0.1dex.
Description:
MOA-2008-BLG-310S and MOA-2008-BLG-311S were observed on two
consecutive nights in 2008 July using the Magellan Inamori Kyocera
Echelle (MIKE) spectrograph on the 6.5m Magellan Clay Telescope at
the Las Campanas Observatory by I. Thompson and G. Burley.
Objects:
------------------------------------------------------------
RA (2000) DE Designation(s)
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17 54 14.4 -34 46 38 MOA-2008-BLG-310S = MOA 2008-BLG-310
17 56 53.7 -31 23 40 MOA-2008-BLG-311S = MOA 2008-BLG-311
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 49 682 Wλ for the sample extremely metal-poor
(EMP) stars from the Hamburg/ESO Survey (HES)
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See also:
J/A+A/512/A41 : Abundances of microlensed stars in the Bulge (Bensby+, 2010)
J/A+A/499/737 : Abundances of microlensed dwarf and subgiant stars (Bensby+,
2009)
J/ApJ/682/1029 : Abundances in OGLE-2007-BLG-349S (Cohen+, 2008)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Name Star designation (MOA-2008-BLG-310S or
MOA-2008-BLG-311S)
19- 25 F7.2 0.1nm lambda Wavelength in Angstroms
27- 31 A5 --- Ion Species identification
33- 36 F4.2 eV ExPot Excitation potential
38- 43 F6.3 [-] log(gf) Log of the oscillator strength
45- 49 F5.1 0.1pm EW ? Equivalent width in milli-Angstroms
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 10-Aug-2011