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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
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: ----------------------------------------------------- RA (2000) DE Designation(s) ----------------------------------------------------- 13 58 33.81 +14 21 08.3 Boo-1137 = [NGW2008] 1137 ----------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 39 154 Averaged equivalent widths, upper limits, and line-by-line abundances of Boo-1137
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) : VALD www interface Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
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]
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).
History: From electronic version of the journal
(End) Emmanuelle Perret [CDS] 03-Apr-2012
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