J/A+A/548/A42 Average spectrum of HD 140283 (370-1040nm) (Siqueira Mello+ 2012)
Origin of the heavy elements in HD 140283. Measurement of europium abundance.
Siqueira Mello C.Jr., Barbuy B., Spite M., Spite F.
<Astron. Astrophys. 548, A42 (2012)>
=2012A&A...548A..42S 2012A&A...548A..42S
ADC_Keywords: Stars, variable ; Abundances
Keywords: Galaxy: halo - stars: abundances - stars: individual: HD 140283 -
Abstract:
HD 140283 is a nearby (V=7.7) subgiant metal-poor star, extensively
analysed in the literature. Although many spectra have been obtained
for this star, none showed a signal-to-noise (S/N) ratio high enough
to enable a very accurate derivation of abundances from weak lines.
The detection of europium proves that the neutron-capture elements in
this star are originate in the r-process, and not in the s-process, as
recently claimed in the literature.
Based on the OSMARCS 1D LTE atmospheric model and with a consistent
approach based on the spectrum synthesis code Turbospectrum, we
measured the europium lines 4129Å and 4205Å, taking into account
the hyperfine structure of the transitions.
The spectrum, obtained with a long exposure time of seven hours at the
Canada-France-Hawaii Telescope (CFHT), has a resolving power of 81000
and a S/N ratio of 800 at 4100Å.
We were able to determine the abundance A(Eu)=-2.35dex, compatible
with the value predicted for the europium from the r-process. The
abundance ratio [Eu/Ba]=+0.58dex agrees with the trend observed in
metal-poor stars and is also compatible with a strong r-process
contribution to the origin of the neutron-capture elements in
HD 140283.
Description:
HD 140283 was observed during the programme 11AB01 at
Canada-France-Hawaii Telescope (CFHT) with the spectrograph ESPaDOnS
in Queued Service Observing (QSO) mode to obtain a spectrum in the
wavelength range 3700Å-10475Å with a resolution of R=81000. The
observations were carried out in 2011, on June 12, 14, 15, and 16 and
on July 8. The total quantity of 23 individual spectra with 20 minutes
of exposure each produced the long exposure time of more than seven
hours. The co-added spectrum was obtained after radial-velocity
correction and its S/N ratio reaches 800-3400 per pixel. Three spectra
were discarded because of their low quality compared with the average.
Objects:
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RA (2000) DE Designation(s)
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15 43 03.10 -10 56 00.6 HD 140283 = HIP 76976
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 49 78 *List of iron lines used in this work
spectrum.dat 17 334950 Average spectrum of HD 140283
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Note on table.dat: The lines were selected from Gallagher et al.
(2010A&A...523A..24G 2010A&A...523A..24G).
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Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 4 A4 ---- Ion Specie of iron line (FeI or FeII)
6- 13 F8.3 0.1nm lambda [3700/10400] Wavelength of the line (Å)
15- 18 F4.2 eV ExcPot Excitation potential
19 A1 --- --- [0]
21- 26 F6.3 [-] loggf Oscillator strength of the transition
28- 31 F4.1 0.1pm EWG Equivalent width measured by Gallagher et al.
(2010A&A...523A..24G 2010A&A...523A..24G)
32 A1 --- --- [0]
34- 38 F5.2 0.1pm EW Equivalent width measured in this work
40- 43 F4.2 [---] A(Fe) Iron abundance (1)
45- 49 F5.2 [Sun] [Fe/H] Abundance ratio (2)
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Note (1): We adopt the notation A(X)=log[n(X)/n(H)]+12, where
n is the number density of atoms.
Note (2): [Fe/H]=A(Fe,star)-A(Fe,☉), with A(Fe,☉)=7.52dex from
Caffau et al. (2011SoPh..268..255C 2011SoPh..268..255C, Solar Chemical Abundances
Determined with a CO5BOLD 3D Model Atmosphere).
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Byte-by-byte Description of file: spectrum.dat
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Bytes Format Units Label Explanations
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1- 10 F10.4 0.1nm lambda [3700/10400] Wavelength in Å
12- 17 F6.4 ---- Flux Normalized flux
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Acknowledgements:
Cesar Siqueira Mello, cesar.mello(at)usp.br
(End) Cesar Siqueira Mello [IAG-USP, Brazil], Patricia Vannier [CDS] 26-Oct-2012