J/A+A/606/A112 Abundance analysis of ALW Carina 8 (Susmitha+, 2017)
Abundance analysis of a CEMP-no star in the Carina dwarf spheroidal galaxy.
Susmitha A., Koch A., Sivarani T.
<Astron. Astrophys. 606, A112 (2017)>
=2017A&A...606A.112S 2017A&A...606A.112S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, carbon ; Abundances
Keywords: stars: abundances - binaries: spectroscopic - stars: carbon -
Galaxy: abundances - galaxies: dwarf
Abstract:
Carbon-enhanced metal-poor (CEMP) stars bear important imprints of the
early chemical enrichment of any stellar system. While these stars are
known to exist in copious amounts in the Milky Way halo, detailed
chemical abundance data from the faint dwarf spheroidal (dSph)
satellites are still sparse, although the relative fraction of these
stars increases with decreasing metallicity. Here, we report the
abundance analysis of a metal-poor ([Fe/H]=-2.5dex),
carbon-rich ([C/Fe]=1.4dex) star, ALW-8, in the Carina dSph
using high-resolution spectroscopy obtained with the ESO/UVES
instrument. Its spectrum does not indicate any over-enhancements of
neutron capture elements. Thus classified as a CEMP-no star, this is
the first detection of this kind of star in Carina. Another of our
sample stars, ALW-1, is shown to be a CEMP-s star, but its immediate
binarity prompted us to discard it from a detailed analysis. The
majority of the 18 chemical elements we measured are typical of
Carina's field star population and also agree with CEMP stars in
other dSph galaxies. Similar to the only known CEMP-no star in the
Sculptor dSph and the weak-r-process star HD 122563, the lack of any
strong barium-enhancement is accompanied by a moderate overabundance
in yttrium, indicating a weak r-process activity. The overall
abundance pattern confirms that, also in Carina, the formation site
for CEMP-no stars has been affected by both faint supernovae and by
standard core collapse supernovae. Whichever process was responsible
for the heavy element production in ALW-8 must be a ubiquitous source
to pollute the CEMP-no stars, acting independently of the environment
such as in the Galactic halo or in dSphs.
Description:
File tableA1.dat contains the linelist for the EW analysis,abundance
and abundance uncertainties to 1 sigma scatter in the stellar
parameters for ALW-8.
Objects:
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RA (2000) DE Designation(s)
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06 41 46.27 -50 58 55.9 ALW-8 = ALW Carina 8
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 54 58 Linelist for the EW analysis, abundance and
abundance uncertainties to 1 sigma scatter in
the stellar parameters for ALW-8
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Element Element name and ionisation
9- 15 F7.2 0.1nm lambda Line wavelength
17- 20 F4.2 eV Chi Exitation potential
22- 27 F6.2 --- loggf Oscillator strength
29- 31 I3 0.1nm EW ? Equivalent width
32 A1 --- n_EW [s] s for syn
34 A1 --- l_A(x) Limit flag on A(x)
35- 39 F5.2 [-] A(x) Abundance
41- 44 F4.2 100K dT Abundance uncertainty to 1 sigma scatter
in the temperature, δT
46- 49 F4.2 [0.25cm/s2] dlogg Abundance uncertainty to 1 sigma scatter
in the gravity, δlogg
51- 54 F4.2 0.2km/s dxi Abundance uncertainty to 1 sigma scatter
in the microturbulent velocity, δxi
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Acknowledgements:
Antony Susmitha, susmitharaniantony(at)gmail.com
(End) Patricia Vannier [CDS] 19-Jun-2017