J/ApJ/791/14 18 Sco atomic data and equivalent widths (Melendez+, 2014)
18 Sco: a solar twin rich in refractory and neutron-capture elements.
Implications for chemical tagging.
Melendez J., Ramirez I., Karakas A.I., Yong D., Monroe T.R., Bedell M.,
Bergemann M., Asplund M., Tucci Maia M., Bean J., Do Nascimento J.-D.Jr,
Bazot M., Alves-Brito A., Freitas F.C., Castro M.
<Astrophys. J., 791, 14 (2014)>
=2014ApJ...791...14M 2014ApJ...791...14M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, dwarfs ; Equivalent widths ; Atomic physics
Keywords: stars: abundances - stars: AGB and post-AGB -
stars: fundamental parameters - Sun: abundances
Abstract:
We study with unprecedented detail the chemical composition and
stellar parameters of the solar twin 18 Sco in a strictly differential
sense relative to the Sun. Our study is mainly based on
high-resolution (R ∼ 110,000), high signal-to-noise ratio (800-1000)
Very Large Telescope UVES spectra, which allow us to achieve a
precision of about 0.005 dex in differential abundances. The effective
temperature and surface gravity of 18 Sco are Teff= 5823±6 K and
log g = 4.45±0.02 dex, i.e., 18 Sco is 46±6 K hotter than the Sun
and log g is 0.01±0.02 dex higher. Its metallicity is
[Fe/H] = 0.054±0.005 dex, and its microturbulence velocity is
+0.02±0.01 km/s higher than solar. Our precise stellar parameters
and differential isochrone analysis show that 18 Sco has a mass of
1.04±0.02 M☉ and that it is ∼1.6 Gyr younger than the Sun. We
use precise High Accuracy Radial velocity Planet Searcher (HARPS)
radial velocities to search for planets, but none are detected. The
chemical abundance pattern of 18 Sco displays a clear trend with
condensation temperature, thus showing higher abundances of
refractories in 18 Sco than in the Sun. Intriguingly, there are
enhancements in the neutron-capture elements relative to the Sun.
Despite the small element-to-element abundance differences among
nearby n-capture elements (∼0.02 dex), we successfully reproduce the
r-process pattern in the Solar System. This is independent evidence
for the universality of the r process. Our results have important
implications for chemical tagging in our Galaxy and nucleosynthesis in
general.
Description:
In order to cover a wide spectral range, we observed 18 Sco and the
Sun (using solar reflected light from asteroids) in different
spectrograph configurations. Both 18 Sco and the reference solar
spectrum were acquired in the same observing runs and using identical
setups. We obtained visitor mode observations with the UVES
spectrograph at the VLT (2009 August 30) and with the HIRES
spectrograph at Keck (2005 June 16), covering with both data sets the
UV/optical/near-IR spectrum from 306 to 1020 nm.
Objects:
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RA (ICRS) DE Designation(s)
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16 15 37.27 -08 22 10.0 18 Sco = HD 146233
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 50 323 Adopted atomic data and equivalent widths
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See also:
J/A+A/544/A106 : p-mode frequencies of the solar twin 18 Sco (Bazot+, 2012)
J/A+A/574/A124 : Spectroscopy of solar twins and analogues (Datson+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 F9.3 0.1nm Wave Wavelength in Angstroms
11- 14 F4.1 --- Ion Ion numeric identifier (1)
16- 21 F6.4 eV ExPot Excitation potential
23- 28 F6.3 [-] log(gf) Log of the oscillator strength times
the statistical weight
31- 38 E8.2 --- C6 Damping constant
40- 44 F5.1 0.1pm EW-18S The 18 Sco differential equivalent width (2)
46- 50 F5.1 0.1pm EW-Sun Solar differential equivalent width (2)
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Note (1): Where the number before the digit is the atomic number and the number
after the digit is the ionization level, e.g. 26.1 = Fe II.
Note (2): In units of milli-Angstroms.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 23-Mar-2017