scholarly journals Strontium in the era of Gaia and LAMOST

2013 ◽  
Vol 9 (S298) ◽  
pp. 409-409
Author(s):  
Camilla J. Hansen ◽  
Elisabetta Caffau ◽  
Maria Bergemann
Keyword(s):  
Chemical Evolution ◽  
Spectral Resolution ◽  
Neutron Capture ◽  
Local Thermodynamic Equilibrium ◽  
Heavy Elements ◽  
Galactic Chemical Evolution ◽  
Non Local ◽  
Formation And Evolution ◽  
Open Question ◽  
Insight Into

AbstractThe formation and evolution of the heavy neutron-capture elements (Z > 37) are to date not well understood. Therefore, abundance and galactic chemical evolution (GCE) studies of these heavy elements may carry key information to this open question. Strontium (Sr) is one of the two heavy elements (Sr and Ba) that show intrinsically very strong absorption lines even in extremely metal-poor stars (and remains detectable at low spectral resolution). Hence, the 4077 Å Sr II line provides a unique insight into the behaviour of heavy neutron-capture elements at all metallicities and resolutions. Here the focus is on strontium, its 3D and NLTE (non-local thermodynamic equilibrium) corrections, as well as chemical evolution.

scholarly journals Heavy Element Nucleosynthesis

2018 ◽  
Vol 184 ◽  
pp. 01007
Author(s):  
Mounib F. El Eid
Keyword(s):  
Chemical Evolution ◽  
Neutron Capture ◽  
Heavy Element ◽  
Slow Neutron ◽  
Heavy Elements ◽  
Galactic Chemical Evolution ◽  
Physical Processes ◽  
The Galaxy ◽  
R Process

This contribution deals with the important subject of the nucleosynthesis of heavy elements in the Galaxy. After an overview of several observational features, the physical processes responsible mainly for the formation of heavy elements will be described and linked to possible stellar sites and to galactic chemical evolution. In particular, we focus on the neutron-capture processes, namely the s-process (slow neutron capture) and the r-process (rapid neutron capture) and discuss some problems in connection with their sites and their outcome. The aim is to give a brief overview on the exciting subject of the heavy element nucleosynthesis in the Galaxy, emphasizing its importance to trace the galactic chemical evolution and illustrating the challenge of this subject.

scholarly journals Carbon and oxygen in metal-poor halo stars

2019 ◽  
Vol 622 ◽  
pp. L4 ◽  
Author(s):  
A. M. Amarsi ◽  
P. E. Nissen ◽  
M. Asplund ◽  
K. Lind ◽  
P. S. Barklem
Keyword(s):  
Chemical Evolution ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Galactic Chemical Evolution ◽  
Elemental Abundances ◽  
Halo Stars ◽  
Effective Temperatures ◽  
Population Iii Stars ◽  
Hydrodynamic Effects ◽  
First Time

Carbon and oxygen are key tracers of the Galactic chemical evolution; in particular, a reported upturn in [C/O] towards decreasing [O/H] in metal-poor halo stars could be a signature of nucleosynthesis by massive Population III stars. We reanalyse carbon, oxygen, and iron abundances in 39 metal-poor turn-off stars. For the first time, we take into account 3D hydrodynamic effects together with departures from local thermodynamic equilibrium (LTE) when determining both the stellar parameters and the elemental abundances, by deriving effective temperatures from 3D non-LTE Hβ profiles, surface gravities from Gaia parallaxes, iron abundances from 3D LTE Fe II equivalent widths, and carbon and oxygen abundances from 3D non-LTE C I and O I equivalent widths. We find that [C/Fe] stays flat with [Fe/H], whereas [O/Fe] increases linearly up to 0.75 dex with decreasing [Fe/H] down to −3.0 dex. Therefore [C/O] monotonically decreases towards decreasing [C/H], in contrast to previous findings, mainly because the non-LTE effects for O I at low [Fe/H] are weaker with our improved calculations.

Abundance ratios & ages of stellar populations in HARPS-GTO sample

2017 ◽  
Vol 12 (S330) ◽  
pp. 156-159 ◽  
Author(s):  
E. Delgado Mena ◽  
M. Tsantaki ◽  
V. Zh. Adibekyan ◽  
S. G. Sousa ◽  
N. C. Santos ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Thin Disk ◽  
Thick Disk ◽  
Heavy Elements ◽  
Galactic Chemical Evolution ◽  
Chemical Abundances ◽  
Homogeneous Sample ◽  
Different Populations ◽  
Search Program ◽  
Cu And Zn

AbstractIn this work we present chemical abundances of heavy elements (Z>28) for a homogeneous sample of 1059 stars from HARPS planet search program. We also derive ages using parallaxes from Hipparcos and Gaia DR1 to compare the results. We study the [X/Fe] ratios for different populations and compare them with models of Galactic chemical evolution. We find that thick disk stars are chemically disjunt for Zn adn Eu. Moreover, the high-alpha metal-rich population presents an interesting behaviour, with clear overabundances of Cu and Zn and lower abundances of Y and Ba with respect to thin disk stars. Several abundance ratios present a significant correlation with age for chemically separated thin disk stars (regardless of their metallicity) but thick disk stars do not present that behaviour. Moreover, at supersolar metallicities the trends with age tend to be weaker for several elements.

Galactic Chemical Evolution of Heavy Elements: From Barium to Europium

1999 ◽  
Vol 521 (2) ◽  
pp. 691-702 ◽  
Author(s):  
Claudia Travaglio ◽  
Daniele Galli ◽  
Roberto Gallino ◽  
Maurizio Busso ◽  
Federico Ferrini ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Heavy Elements ◽  
Galactic Chemical Evolution

Galactic Chemical Evolution of the Lighter Neutron Capture Elements Sr, Y and Zr

2003 ◽  
Vol 3 (5) ◽  
pp. 431-442 ◽  
Author(s):  
Cui-Hua Du ◽  
Bo Zhang ◽  
Han-Feng Song ◽  
Qiu-He Peng
Keyword(s):  
Chemical Evolution ◽  
Neutron Capture ◽  
Galactic Chemical Evolution

scholarly journals Observational constraints on the origin of the elements

2020 ◽  
Vol 635 ◽  
pp. A38 ◽  
Author(s):  
P. Eitner ◽  
M. Bergemann ◽  
C. J. Hansen ◽  
G. Cescutti ◽  
I. R. Seitenzahl ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Globular Clusters ◽  
Local Thermodynamic Equilibrium ◽  
Galactic Chemical Evolution ◽  
Galactic Disc ◽  
Milky Way Galaxy ◽  
Halo Stars ◽  
Type Ia ◽  
Low Metallicity ◽  
Different Sources

The abundance ratios of manganese to iron in late-type stars across a wide metallicity range place tight constraints on the astrophysical production sites of Fe-group elements. In this work, we investigate the chemical evolution of Mn in the Milky Way galaxy using high-resolution spectroscopic observations of stars in the Galactic disc and halo stars, as well as a sample of globular clusters. Our analysis shows that local thermodynamic equilibrium (LTE) leads to a strong imbalance in the ionisation equilibrium of Mn I and Mn II lines. Mn I produces systematically (up to 0.6 dex) lower abundances compared to the Mn II lines. Non-LTE (NLTE) radiative transfer satisfies the ionisation equilibrium across the entire metallicity range, of −3 ≲ [Fe/H] ≲ −1, leading to consistent abundances from both ionisation stages of the element. We compare the NLTE abundances with Galactic Chemical Evolution models computed using different sources of type Ia and type II supernova (SN Ia and SN II) yields. We find that a good fit to our observations can be obtained by assuming that a significant (∼75%) fraction of SNe Ia stem from a sub-Chandrasekhar (sub-Mch) channel. While this fraction is larger than that found in earlier studies (∼50%), we note that we still require ∼25% near-Mch SNe Ia to obtain solar [Mn/Fe] at [Fe/H] = 0. Our new data also suggest higher SN II Mn yields at low metallicity than typically assumed in the literature.

scholarly journals Fundamental stellar properties from asteroseismology

2013 ◽  
Vol 9 (S298) ◽  
pp. 375-380 ◽  
Author(s):  
Víctor Silva Aguirre ◽  
Luca Casagrande ◽  
Andrea Miglio
Keyword(s):  
Chemical Evolution ◽  
Galactic Disk ◽  
Stellar Populations ◽  
Solar Neighborhood ◽  
Galactic Chemical Evolution ◽  
Fundamental Parameters ◽  
Large Samples ◽  
Formation And Evolution ◽  
Stellar Properties

AbstractAccurate characterization of stellar populations is of prime importance to correctly understand the formation and evolution process of our Galaxy. The field of asteroseismology has been particularly successful in such an endeavor providing fundamental parameters for large samples of stars in different evolutionary phases. We present our results on determinations of masses, radii, and distances of stars in the CoRoT and Kepler fields, showing that we can map and date different regions of the galactic disk and distinguish gradients in the distribution of stellar properties at different heights. We further review how asteroseismic determinations can produce a unique set of constraints, including ages, outside the solar neighborhood for galactic chemical evolution models.

scholarly journals Nucleosynthesis imprints from different Type Ia supernova explosion scenarios and implications for galactic chemical evolution

2020 ◽  
Vol 644 ◽  
pp. A118
Author(s):  
F. Lach ◽  
F. K. Röpke ◽  
I. R. Seitenzahl ◽  
B. Coté ◽  
S. Gronow ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
White Dwarfs ◽  
Supernova Explosion ◽  
Detailed Comparison ◽  
Galactic Chemical Evolution ◽  
Type Ia Supernova ◽  
Type Ia ◽  
Pure Helium ◽  
Ia Supernovae ◽  
Insight Into

We analyze the nucleosynthesis yields of various Type Ia supernova explosion simulations including pure detonations in sub-Chandrasekhar mass white dwarfs; double detonations and pure helium detonations of sub-Chandrasekhar mass white dwarfs with an accreted helium envelope; a violent merger model of two white dwarfs; and deflagrations and delayed detonations in Chandrasekhar mass white dwarfs. We focus on the iron peak elements Mn, Zn, and Cu. To this end, we also briefly review the different burning regimes and production sites of these elements, as well as the results of abundance measurements and several galactic chemical evolution studies. We find that super-solar values of [Mn/Fe] are not restricted to Chandrasekhar mass explosion models. Scenarios including a helium detonation can significantly contribute to the production of Mn, in particular the models proposed for calcium-rich transients. Although Type Ia supernovae are often not accounted for as production sites of Zn and Cu, our models involving helium shell detonations can produce these elements in super-solar ratios relative to Fe. Our results suggest a re-consideration of Type Ia supernova yields in galactic chemical evolution models. A detailed comparison with observations can provide new insight into the progenitor and explosion channels of these events.

scholarly journals Laboratory transition probabilities for studies of nucleosynthesis of Fe-group elements1

2017 ◽  
Vol 95 (9) ◽  
pp. 783-789 ◽  
Author(s):  
J.E. Lawler ◽  
C. Sneden ◽  
J.J. Cowan ◽  
E.A. Den Hartog ◽  
M.P. Wood
Keyword(s):  
Chemical Evolution ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Transition Probabilities ◽  
Laboratory Data ◽  
Galactic Chemical Evolution ◽  
One Dimensional ◽  
Elemental Abundances ◽  
Yield Information ◽  
Early Galaxy

The synthesis of iron (Fe-) group elements was different in the early Galaxy than it is today. Measurements of the relative Fe-group elemental abundances in old metal-poor stars yield information on the Galactic chemical evolution and some information on early supernovae (SNe). Improved laboratory data on transition probabilities is essential to this effort. It is also essential to understand and map the limits of standard photospheric models based on one-dimensional and local thermodynamic equilibrium approximations.

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