NLTE abundances of Mn in a sample of metal-poor stars ⋆

By M. Bergemann, T. H. I. F. Astronomy, Astrophysics, Ludwig-Maximilian University, Munich, Heidelberg · Germany. 2008

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Aims. Following our solar work, we perform NLTE calculations of the Mn abundance for fourteen stars with [Fe/H] from 0 to -2.5, mainly to show how NLTE affects Mn abundances in cool stars of different metallicities. Methods. The spectrum synthesis and Mn abundances are based on statistical equilibrium calculations using various estimates fo r the influence of hydrogen collisions. Results. The NLTE abundances of Mn in all studied stars are systematically higher than the LTE abundances. At low metallicities, the NLTE abundance corrections may run up to 0.5 - 0.7 dex. Instead of a strong depletion of Mn relative to Fe in metal-poor stars as found by the other authors, we only find slightly subsolar values of [Mn /Fe] throughout the range of metallicities analyzed here. Conclusions. The [Mn/Fe] trend in metal-poor stars is inconsistent with the predi ctions of galactic chemical evolution models, where Mn is less produced than Fe.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/9abb0471a5dee8d0782694a755bbfec161e05a57

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Nucleosynthesis in Stars and the Chemical Enrichment of Galaxies (2013, background): “For Mn, the NLTE effect should not be so large, which is indicated by MnII observations (but see Bergemann & Gehren 2008).”
STELLAR ABUNDANCES IN THE SOLAR NEIGHBORHOOD: THE HYPATIA CATALOG (2014, background): “Manganese could have formed from either core collapse supernovae or SN Ia, but it is difficult to tell which is dominating the trend for [Fe/H] > -1.0 dex (Chen et al. 2000; Prochaska & McWilliam 2000; McWilliam et al. 2003; Bergemann & Gehren 2007; Feltzing et al. 2007; Bergemann & Gehren 2008).”
THE MOST METAL-POOR STARS. II. CHEMICAL ABUNDANCES OF 190 METAL-POOR STARS INCLUDING 10 NEW STARS WITH [Fe/H] ⩽ −3.5,, (2012, background): “…corrections, although we recognize the magnitude of such efforts currently underway (e.g., Andrievsky et al. 2008, 2011; Collet et al. 2011; Bergemann & Gehren 2008; Bergemann et al. 2010; Bergemann 2011; Bergemann et al. 2012; Dobrovolskas et al. 2012; Lind et al. 2009a, 2011, 2012; Spite…”
The evolution of isotope ratios in the Milky Way Galaxy (2011, background): “For Mn, the NLTE effect should not be so large as indicated by Mn II observations (Johnson 2002; Mashonkina et al. 2010), although a strong NLTE effect is reported by Bergemann & Gehren (2008).”
Gaia FGK benchmark stars: Effective temperatures and surface gravities (2015, background): “…as test objects in a series of investigations of non-LTE line formation for several chemical elements (Ca I and Ca II in Mashonkina et al. 2007; eight elements in Mashonkina et al. 2008; Mn I in Bergemann & Gehren 2008; Co I and Co II in Bergemann et al. 2010; Mg I in Mashonkina 2013).”
Quantifying the uncertainties of chemical evolution studies II. Stellar yields (2010, methodology): “To our knowledge, there is only one work dealing with the important issue of non-LTE line formation for Mn (Bergemann & Gehren 2008).”
SPECTRAL PROPERTIES OF COOL STARS: EXTENDED ABUNDANCE ANALYSIS OF 1,617 PLANET-SEARCH STARS (2016, background): “At metallicities below -0.4, NLTE effects become important and seem to change any downward trend into a plateau (Battistini & Bensby 2015; Bergemann & Gehren 2008).”