2010A&A...522A...9B


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.16CEST21:38:11

2010A&A...522A...9B - Astronomy and Astrophysics, volume 522, A9-9 (2010/11-1)

Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy.

BERGEMANN M. and CESCUTTI G.

Abstract (from CDS):

We investigate statistical equilibrium of Cr in the atmospheres of late-type stars to ascertain whether the systematic abundance discrepancy between CrI and CrII lines, as often found in previous work, is due to deviations from local thermodynamic equilibrium (LTE). Furthermore, we attempt to interpret the Non-LTE (NLTE) trend of [Cr/Fe] with [Fe/H] using chemical evolution models for the solar neighborhood. NLTE calculations are performed for the model of the Cr atom, comprising 340 levels and 6806 transitions in total. We use the quantum-mechanical photoionization cross-sections of Nahar (2009, Journal of Quantitative Spectroscopy and Radiative Transfer, 110, 2148) and investigate the sensitivity of the model to uncertain cross-sections for H I collisions. NLTE line formation is performed for the MAFAGS-ODF model atmospheres of the Sun and 10 metal-poor stars with -3.2<[Fe/H]←0.5, and Cr abundances are derived by comparing the synthetic and observed flux spectra. We achieve good ionization equilibrium of Cr for models with different stellar parameters, if inelastic collisions with H I atoms are neglected. The solar NLTE abundance based on CrI lines is 5.74dex with σ=0.05dex, which is ∼0.1dex higher than the LTE abundance. For the metal-poor stars, the NLTE abundance corrections to CrI lines range from +0.3 to +0.5dex. The resulting [Cr/Fe] ratio is roughly solar for the range of metallicities analyzed here, which is consistent with current views on the production of these iron peak elements in supernovae. The tendency of Cr to become deficient with respect to Fe in metal-poor stars is an artifact caused by the neglect of NLTE effects in the line formation of CrI, and has no relation to any peculiar physical conditions in the Galactic ISM or deficiencies of nucleosynthesis theory.

Abstract Copyright:

Journal keyword(s): line: formation - line: profiles - Sun: abundances - stars: abundances - nuclear reactions, nucleosynthesis, abundances - Galaxy: evolution

Simbad objects: 10

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Number of rows : 10

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 HD 19445 PM* 03 08 25.5884 +26 19 51.400 8.29 8.52 8.06 7.60 7.27 G2VFe-3 732 0
2 HD 34328 PM* 05 13 05.2763883242 -59 38 44.266050124   9.95 9.46     G0wA8V 117 0
3 HD 84937 PM* 09 48 56.09801 +13 44 39.3237 8.49 8.68 8.32 7.97 7.70 F8Vm-5 704 0
4 HD 102200 Pe* 11 45 34.2344518332 -46 03 46.386462682   9.13 8.76     F2V 94 0
5 BD-04 3208 PM* 12 07 15.0719832426 -05 44 01.609304815   10.40 9.99     A7 131 0
6 Wolf 1492 Pe* 13 40 02.4921790616 -00 02 18.750321114 11.601 11.832 11.451 11.184 10.892 sdF0: 255 0
7 HD 122196 PM* 14 01 02.1244272306 -38 03 03.297565043   9.19 8.75     F0(V)w 106 0
8 HD 123710 PM* 14 04 57.0712635984 +74 34 24.892571708   8.79   7.8   G5 59 0
9 HD 140283 Pe* 15 43 03.0967798658 -10 56 00.595803430 7.508 7.711 7.212 6.63 8.21 F9VkA5mA1 845 0
10 HD 148816 PM* 16 30 28.4586643435 +04 10 41.603810207 7.75 7.81 7.28 6.82 6.49 F7V 277 0

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2019.10.16-21:38:11

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