Mega (metal-poor) not so much : Non-LTE spectroscopic stellar parameters and abundance determination of Ultra metal-poor stars

2017 ◽  
Vol 13 (S334) ◽  
pp. 259-262 ◽  
Author(s):  
Rana Ezzeddine ◽  
Tatyana Sitnova ◽  
Anna Frebel ◽  
Lyudmilla Mashonkina ◽  
Bertrand Plez
Keyword(s):  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Chemical Species ◽  
First Stars ◽  
Absolute Value ◽  
Non Local ◽  
Abundance Determination

AbstractWe present Non-Local Thermodynamic Equilibrium (Non-LTE) abundance corrections for Mg, Ca, and Fe in 12 ultra metal-poor (UMP) stars ([Fe/H] < −4.00). We show that they increase in absolute value toward the lower metallicity up to 0.45 dex for Mg, 0.30 dex for Ca, and 1.00 dex for Fe. This represents a first step toward a full Non-LTE analysis of chemical species in the UMP stars that will enable us to put useful constraints on the properties of the “First” stars.

scholarly journals Determination of corona, LTE, and NLTE regimes of optically thin carbon plasmas

2008 ◽  
Vol 26 (1) ◽  
pp. 21-32 ◽  
Author(s):  
J.M. Gil ◽  
R. RodrÍguez ◽  
R. Florido ◽  
J.G. Rubiano ◽  
P. Martel ◽  
...  
Keyword(s):  
Steady State ◽  
Plasma Density ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Radiative Properties ◽  
Thin Carbon ◽  
Non Local

AbstractIn this work is accomplished the determination of the corona, local and non-local thermodynamic equilibrium regimes for optically thin carbon plasmas in steady state, in terms of the plasma density and temperature using the ABAKO code. The determination is made through the analysis of the plasma average ionization and ion and level populations. The results are compared whit those obtained applying Griem's criterion. Finally, it is made a brief analysis of the effects of the calculation of level populations assuming different plasma regimes in radiative properties, such as emissivities and opacities.

Diagnosing Fe Plasma In Non-Local Thermodynamic Equilibrium

2013 ◽  
Vol 82 (2) ◽  
pp. 024501
Author(s):  
Xiao-Ying Han ◽  
Fei-Lu Wang ◽  
Ze-Qing Wu ◽  
Jun Yan ◽  
Gang Zhao
Keyword(s):  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Non Local

scholarly journals On the violation of local thermodynamic equilibrium in the plasma jet of an argon arc two-jet plasmatron

2019 ◽  
Vol 85 (1II)) ◽  
pp. 145-150
Author(s):  
A. S. Cherevko ◽  
A. A. Morozova
Keyword(s):  
Energy Level ◽  
Equilibrium State ◽  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Plasma Jet ◽  
Saha Equation ◽  
Radiation Processes ◽  
Unconventional Method

The degree and nature of the violation of local thermodynamic equilibrium (LTE) in the analytical zone of a plasma jet generated by an argon arc two-jet plasmatron (TJP) was estimated using an unconventional method based on determination of the nonequilibrium parameterbiequal to the ratio of the experimentally determined actual population of the energy level (ni) of the element to the population of the same level calculated from the Saha equation (nis). Partial ionizing deviation of plasma under study from the equilibrium state takes place only when low-lying atomic levels are overpopulated. The distinct dependence ofbion the ionization potential of the considered element (e.g., Ca, Mg, and Be) is shown. The results were interpreted in the light of the increasing role of radiation processes upon excitation of spectra in the argon arc two-jet plasmatron.

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