J/ApJ/681/1524 Detailed abundances for 28 metal-poor stars (Lai+, 2008)
Detailed abundances for 28 metal-poor stars: stellar relics in the Milky Way.
Lai D.K., Bolte M., Johnson J.A., Lucatello S., Heger A., Woosley S.E.
<Astrophys. J., 681, 1524-1556 (2008)>
=2008ApJ...681.1524L 2008ApJ...681.1524L
ADC_Keywords: Equivalent widths ; Abundances, [Fe/H] ; Effective temperatures ;
Stars, metal-deficient
Keywords: nuclear reactions, nucleosynthesis, abundances - stars: abundances -
stars: Population II - supernovae: general
Abstract:
We present the results of an abundance analysis for a sample of stars
with -4<[Fe/H]←2. The data were obtained with the HIRES spectrograph
at Keck Observatory. The set includes 28 stars, with effective
temperature ranging from 4800 to 6600K. For 13 stars with [Fe/H]←2.6,
including nine with [Fe/H]←3.0 and one with [Fe/H]=-4.0, these are
the first reported detailed abundances. For the most metal-poor star
in our sample, CS 30336-049, we measure an abundance pattern that is
very similar to stars in the range [Fe/H]~-3.5, including a normal
C+N, abundance. We also find that it has very low but measurable Sr
and Ba, indicating some neutron-capture activity even at this low of a
metallicity. We explore this issue further by examining other very
neutron capture-deficient stars and find that, at the lowest levels,
[Ba/Sr] exhibits the ratio of the main r-process. We also report on a
new r-process-enhanced star, CS 31078-018. This star has
[Fe/H]=-2.85, [Eu/Fe]=1.23, and [Ba/Eu]=-0.51. CS 31078-018 exhibits
an "actinide boost," i.e., much higher [Th/Eu] than expected and at a
similar level to CS 31082-001. Our spectra allow us to further
constrain the abundance scatter at low metallicities, which we then
use to fit to the zero-metallicity Type II supernova yields of Heger &
Woosley (2008arXiv0803.3161H 2008arXiv0803.3161H). We find that supernovae with progenitor
masses between 10 and 20M☉ provide the best matches to our
abundances.
Description:
The data were obtained from multiple runs at the HIRES spectrograph at
Keck Observatory between 2001 and 2006. We chose our sample from Lai
et al. (2004, Cat. J/AJ/128/2402) and metal-poor candidates identified
in the photometric sample of Schuster et al. (2004, Cat. J/A+A/422/527).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 79 28 Stellar parameters
width.dat 44 12659 Equivalent widths and atomic parameters for the
28 stars (tables 2, 3 and 4 of the paper)
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See also:
III/211 : Keck/HIRES Sky Line Atlas (Osterbrock+ 1997)
J/A+A/305/245 : Fe I in metal-poor stars (Magain+, 1996)
J/A+A/356/238 : Atmospheric parameters in metal-poor stars. III. (Carretta+,
2000)
J/A+A/404/187 : Equivalent widths for metal-poor stars (Gratton+, 2003)
J/AJ/128/2402 : Extremely metal-poor star candidates abundances (Lai+, 2004)
J/A+A/422/527 : Metal-poor star uvby-beta photometry. X. (Schuster+, 2004)
J/A+A/440/321 : Chemical abundances in 43 metal-poor stars (Jonsell+, 2005)
J/A+A/522/A26 : Fe Abundances in metal-poor stars (Sbordone+ 2010)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Star identification
13- 17 F5.2 [Sun] [Fe/H] Metallicity
19- 22 I4 K Teff Effective temperature (1)
24- 27 F4.2 [cm/s2] logg Surface gravity
29- 31 F3.1 km/s vt Microturbulence velocity
33- 37 F5.2 [eV] Chi Slope of the trend for all lines (2)
39- 43 F5.2 --- r Corresponding correlation coefficient for all
lines
45- 47 I3 --- N Number of FeI lines used for all lines
49- 53 F5.2 [eV] Chi02 Slope of the trend for χ>0.2eV
55- 59 F5.2 --- r02 Corresponding correlation coefficient for
χ>0.2eV
61- 63 I3 --- N02 Number of FeI lines used for χ>0.2eV
65- 69 F5.2 [eV] Chi12 Slope of the trend for χ>1.2eV
71- 75 F5.2 --- r12 Corresponding correlation coefficient for
χ>1.2eV
77- 79 I3 --- N12 Number of FeI lines used for χ>1.2eV
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Note (1): Effective temperatures are obtained using the V-K color of each star.
Note (2): Slope per dex(eV); see section 3.3.1 for more details.
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Byte-by-byte Description of file: width.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Star designation
13- 19 F7.2 0.1nm Wave Wavelength in Angstroms
21 A1 --- f_Wave [*] Flag on Wave (1)
23- 26 F4.1 --- Element Element identification
28- 32 F5.2 [-] log(gf) Log of the oscillator strength
34- 37 F4.2 eV ExPot Excitation potential
39- 44 F6.2 10-13m EW ? Equivalent width (mÅ)
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Note (1):
* = abundance was derived through spectral synthesis. Except for the Al
lines, all of these lines take into account hyperfine splitting (HFS).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 03-Nov-2010