J/A+A/643/A49 Linelist (Hansen+, 2020)
Mono-enriched stars and Galactic chemical evolution.
Possible biases in observations and theory.
Hansen C.J., Koch A., Mashonkina L., Magg M., Bergemann M., Sitnova T.,
Gallagher A.J., Ilyin I., Caffau E., Zhang H.W., Strassmeier K.G.,
Klessen R.S.
<Astron. Astrophys. 643, A49 (2020)>
=2020A&A...643A..49H 2020A&A...643A..49H (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: stars: abundances - stars: kinematics and dynamics - Galaxy: halo -
nuclear reactions, nucleosynthesis, abundances -
stars: Population II - stars: Population III
Abstract:
A long sought after goal using chemical abundance patterns derived
from metal- poor stars is to understand the chemical evolution of the
Galaxy and to pin down the nature of the first stars (Pop III).
Metal-poor, old, unevolved stars are excellent tracers as they
preserve the abundance pattern of the gas from which they were born,
and hence they are frequently targeted in chemical tagging studies.
Here, we use a sample of 14 metal-poor stars observed with the
high-resolution spectrograph called the Potsdam Echelle Polarimetric
and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope
(LBT) to derive abundances of 32 elements (34 including upper limits).
We present well-sampled abundance patterns for all stars obtained
using local thermodynamic equilibrium (LTE) radiative transfer codes
and one-dimensional(1D) hydrostatic model atmospheres. However, it is
currently well-known that the assumptions of 1D and LTE may hide
several issues, thereby introducing biases in our interpretation as to
the nature of the first stars and the chemical evolution of the
Galaxy. Hence, we use non-LTE (NLTE) and correct the abundances using
three-dimensional (3D) model atmospheres to present a physically more
reliable pattern. In order to infer the nature of the first stars, we
compare unevolved, cool stars, which have been enriched by a single
event ('mono-enriched'), with a set of yield predictions to pin down
the mass and energy of the Pop∼III progenitor. To date, only few bona
fide second generation stars that are mono-enriched are known. A
simple chi2-fit may bias our inferred mass and energy just as much
as the simple 1D LTE abundance pattern, and we therefore carried out
our study with an improved fitting technique considering dilution and
mixing. Our sample presents Carbon Enhanced Metal-Poor (CEMP) stars,
some of which are promising bona fide second generation
(mono-enriched) stars. The unevolved, dwarf BD+09 2190 shows a
mono-enriched signature which, combined with kinematical data,
indicates that it moves in the outer halo and likely has been accreted
onto the Milky Way early on. The Pop∼III progenitor was likely of
25.5M☉ and 0.6foe (0.6x1051erg) in LTE and 19.2M☉ and
1.5foe in NLTE, respectively. Finally, we explore the predominant
donor and formation site of the rapid and slow neutron-capture
elements. In BD-10 3742, we find an almost clean r-process trace, as
is represented in the star HD20, which is a 'metal-poor Sun benchmark'
for the r-process, while TYC5481-00786-1 is a promising CEMP-r/-s
candidate that may be enriched by an asymptotic giant branch star of
an intermediate mass and metallicity.
Description:
Linelist containing wavelength, element and ionisation degree (0 =
neutral, 1 = single ionised), excitation potential [eV], oscillator
strength (loggf), number of stars in the study in which the line has
been detected (limits indicated by <), and finally, hyperfine
structure of oscillator strength indicated by HFS.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
linelist.dat 34 243 Linelist with atomic data
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Byte-by-byte Description of file: linelist.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm lambda Wavelength
9- 12 F4.1 -- El Element and ionisation
14- 19 F6.3 eV EP Excitation potential
21- 26 F6.3 [-] loggf Oscillator strength
28 A1 --- l_Number Limit flag on Number
29- 30 I2 -- Number Number of stars with line detected
32- 34 A3 -- HFS Flag indicating hyperfine split loggf used
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Acknowledgements:
Camilla Juul Hansen, hansen(at)mpia.de
(End) Camilla Juul Hansen [MPIA, Germany], Patricia Vannier [DS] 08-Oct-2020