J/A+A/645/A64 Potential omega Cen associate EW (Koch-Hansen+, 2021)
Purveyors of fine halos.
III. Chemical abundance analysis of a potential omega Cen associate.
Koch-Hansen, A., Hansen, C.J., Lombardo, L., Bonifacio, P., Hanke, M.,
Caffau. E.
<Astron. Astrophys. 645, A64 (2021)>
=2021A&A...645A..64K 2021A&A...645A..64K (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Equivalent widths ; Abundances
Keywords: Galaxy: abundances - Galaxy: formation -
Galaxy: globular clusters: general -
globular clusters: individual: omega Centauri - Galaxy: halo -
Galaxy: stellar content
Abstract:
Globular clusters (GCs) are important donors to the build-up of the
Milky Way (MW) stellar halo, having contributed at the ten percent
level over the Galactic history. Stars that originated from the second
generation of dissolved or dissolving clusters can be readily
identified via distinct light-element signatures such as enhanced N
and Na and simultaneously depleted C and O abundances. In this paper
we present an extensive chemical abundance analysis of the halo star
J110842, which was previously kinematically associated with the
massive MW GC ω Centauri (ω Cen), and we discuss viable
scenarios from escape to encounter. Based on a high-resolution, high
signal-to-noise spectrum of this star using the UVES spectrograph, we
were able to measure 33 species of 31 elements across all
nucleosynthetic channels. The star's low metallicity of
[FeII/H]=2.10±0.02(stat.)±0.07(sys.) dex places it in the lower
sixth percentile of ω Cen's metallicity distribution. We find
that all of the heavier-element abundances, from - and Fepeak elements
to neutron-capture elements are closely compatible with ω
Cen's broad abundance distribution. However, given the major overlap
of this object's abundances with the bulk of all of the MW
components, this does not allow for a clear-cut distinction of the
star's origin. In contrast, our measurements of an enhancement in CN
and its position on the Na-strong locus of the Na-O anticorrelation
render it conceivable that it originally formed as a second-generation
GC star, lending support to a former association of this halo star
with the massive GC ω Cen.
Description:
We performed a standard abundance analysis that employed a mixture of
equivalent width (EW) measurements, carried out via Gaussian fits with
the IRAF splot task, and spectrum synthesis. Here we employed the same
line list as in Koch & McWilliam (2014, Cat. J/A+A/565/A23, see Table 2)
with further additions in the syntheses from Biemont et al.
(2000MNRAS.312..116B 2000MNRAS.312..116B), Den Hartog et al. (2003ApJS..148..543D 2003ApJS..148..543D), Den
Hartog et al. (2006, Cat. J/ApJS/167/292), Lawler et al. (2007, Cat.
J/ApJS/169/120), Lawler et al. (2008ApJS..178...71L 2008ApJS..178...71L), Lawler et al.
(2009, Cat. J/ApJS/182/51), Sneden et al. (2009, Cat. J/ApJS/182/80),
and Hansen et al. (2013A&A...551A..57H 2013A&A...551A..57H).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 35 219 Line list
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See also:
J/A+A/637/A98 : Globular cluster escapees in the Galactic halo (Hanke+, 2020)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm Wave Wavelength
9- 13 A5 --- Ion Ion designation
15- 18 F4.2 eV EP Excitation potential
20- 26 F7.3 [-] loggf Oscillator strength
28- 32 F5.1 10-13m EW ? Mean equivalent width, in milli-Angstroems
33- 35 A3 --- n_EW [Syn] "Syn" denotes that abundances were
derived from spectral synthesis
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Acknowledgements:
Andreas Koch-Hansen, Andreas.Koch(at)uni-heidelberg.de
References:
Koch et al., Paper I 2019A&A...625A..75K 2019A&A...625A..75K
Hanke et al., Paper II 2020A&A...637A..98H 2020A&A...637A..98H, Cat. J/A+A/637/A98
(End) Patricia Vannier [CDS] 10-Nov-2020