J/ApJ/711/350 Metal-poor giant Boo-1137 abundances (Norris+, 2010)
Boo-1137--an extremely metal-poor star in the ultra-faint dwarf spheroidal
galaxy Bootes I.
Norris J.E., Yong D., Gilmore G., Wyse R.F.G.
<Astrophys. J., 711, 350-360 (2010)>
=2010ApJ...711..350N 2010ApJ...711..350N
ADC_Keywords: Abundances ; Equivalent widths ; Stars, metal-deficient ;
Stars, giant ; Galaxies, nearby
Keywords: Galaxy: abundances - galaxies: abundances - galaxies: dwarf -
galaxies: individual (Bootes I) - stars: abundances
Abstract:
We present high-resolution (R∼40000), high-signal-to-noise ratio
(20-90) spectra of an extremely metal-poor giant star Boo-1137 in the
"ultra-faint" dwarf spheroidal galaxy (dSph) Bootes I, absolute
magnitude MV~-6.3. We derive an iron abundance of [Fe/H]=-3.7,
making this the most metal-poor star as yet identified in an
ultra-faint dSph. Our derived effective temperature and gravity are
consistent with its identification as a red giant in Bootes I.
Abundances for a further 15 elements have also been determined.
Comparison of the relative abundances, [X/Fe], with those of the
extremely metal-poor red giants of the Galactic halo shows that
Boo-1137 is "normal" with respect to C and N, the odd-Z elements Na
and Al, the iron-peak elements, and the neutron-capture elements Sr
and Ba, in comparison with the bulk of the Milky Way halo population
having [Fe/H]≲-3.0. The α-elements Mg, Si, Ca, and Ti are all
higher by Δ[X/Fe]∼0.2 than the average halo values. Monte Carlo
analysis indicates that Δ[α/Fe] values this large are
expected with a probability ∼0.02. The elemental abundance pattern in
Boo-1137 suggests inhomogeneous chemical evolution, consistent with
the wide internal spread in iron abundances we previously reported.
Description:
Boo-1137 was observed at the VLT Unit Telescope 2 (UT2) with the
UVES (Ultraviolet and Visual Echelle Spectrograph) during the nights
of 2009 April 24 and 25. Ten individual exposures with an integration
time of 46 minutes each were obtained.
Objects:
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RA (2000) DE Designation(s)
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13 58 33.81 +14 21 08.3 Boo-1137 = [NGW2008] 1137
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 39 154 Averaged equivalent widths, upper limits, and
line-by-line abundances of Boo-1137
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See also:
B/eso : ESO Science Archive Catalog (ESO, 2012)
J/A+A/501/519 : Extremely metal-poor turnoff stars abundances (Bonifacio+,
2009)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/A+A/403/1105 : Extremely metal-poor giants equivalent widths (Francois+,
2003)
http://www.astro.uu.se/~vald/php/vald.php : VALD www interface
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Ion Species identification
7- 14 F8.3 0.1nm lambda Wavelength in Å
16- 19 F4.2 eV chi Lower excitation potential (1)
21- 25 F5.2 --- loggf Oscillator strength (1)
27 A1 --- f_loggf [a] a: loggf from VALD
29- 33 F5.1 0.1pm EW Equivalent width in mÅ
35- 39 F5.2 [-] log(e) ε abundance [log(Ion/H)+12]
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Note (1): Lower excitation potentials, χ, and loggf values are taken
preferentially from Table 3 of Cayrel et al. (2004,
Cat. J/A+A/416/1117), and supplemented by material from the Vienna
Atomic Line Database (VALD) database (if flagged in column f_loggf).
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 03-Apr-2012