Non-LTE line formation of Fe in late-type stars - II. 1D spectroscopic stellar parameters

By K. Lind, M. Bergemann, Martin Asplund. 2012

256 citations recorded by the source corpus.

We investigate departures from local thermodynamic equilibrium (NLTE) in the line formation of neutral and singly ionised iron lines and their impac t on spectroscopic stellar parameters. The calculations are performed for an extensive grid of 1D MARCS models of metal-rich and metal-poor late-type dwarfs and giants. We find that iron abundances derived from Fe I lines are increasingly underestimated in hotter, lower sur face-gravity, and more metal-poor stars, in a simple and well-defined pattern, while LTE is usua lly a realistic approximation for Fe II lines. For the vast majority of dwarfs and giants, the pe rturbed ionisation balance of Fe I and Fe II is the main relevant NLTE effect to consider in the determination of spectroscopic parameters, while for extremely metal-poor stars and hot giant stars significant impact is seen also on the excitation balance and on the microturbulence determination from Fe I lines.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/98ea1b9a164b0b4fec88707eb475fc227a285c33

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Citations in the corpus

SPECTRAL PROPERTIES OF COOL STARS: EXTENDED ABUNDANCE ANALYSIS OF 1,617 PLANET-SEARCH STARS (2016, methodology): “We obtained corrections for lines in common with our line list of oxygen (Amarsi et al. 2015), sodium (Lind et al. 2011), magnesium (Osorio et al. 2015), titanium (Bergemann 2011), and iron (Bergemann et al. 2012; Lind et al. 2012).”
A SEARCH FOR STARS OF VERY LOW METAL ABUNDANCE. VI. DETAILED ABUNDANCES OF 313 METAL-POOR STARS (2014, background): “Lind et al. (2012) have considered how line-by-line departures from LTE on Fe i and Fe ii lines can act to influence the derivation of stellar parameters.”
THE MOST METAL-POOR STARS. II. CHEMICAL ABUNDANCES OF 190 METAL-POOR STARS INCLUDING 10 NEW STARS WITH [Fe/H] ⩽ −3.5,, (2012, background): “For our sample of program stars (red generalized histograms in Figure 11), there is evidence for overionization (our sample is, on average, more metal-poor than the full sample, and Lind et al. 2012 show that the degree of overionization is a function of metallicity).”
OXYGEN ABUNDANCES IN NEARBY FGK STARS AND THE GALACTIC CHEMICAL EVOLUTION OF THE LOCAL DISK AND HALO (2013, unknown): “We refer the reader to the recent works by Bergemann et al. (2012) and Lind et al. (2012) for a detailed investigation of these issues.”
High-precision abundances of elements in solar twin stars - Trends with stellar age and elemental condensation temperature (2015, methodology): “The detailed calculations by Lind et al. (2012) show that Feii lines are not affected by departures from LTE, but as mentioned in Sect.”
Gaia FGK benchmark stars: Effective temperatures and surface gravities (2015, result): “Recent studies of nonLTE line formation of Fe (Bergemann et al. 2012b; Lind et al. 2012) indeed predict differential non-LTE corrections for stars similar to β Gem and Vir in the sense described above; however, the magnitude of the effect is much smaller.”
The Gaia-ESO Survey : radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk (2014, methodology): “SME has been recently upgraded by the module to solve for NLTE line formation using the Fe grids described in Lind et al. (2012).”
Exploring the Milky Way stellar disk - A detailed elemental abundance study of 714 F and G dwarf stars in the solar neighbourhood (2013, methodology): “We have done that by using the NLTE calculations for Fei lines by Lind et al. (2012).”
The GALAH survey: observational overview and Gaia DR1 companion (2016, methodology): “The SME synthesis employs MARCS model atmospheres (Gustafsson et al. 2008), and includes NLTE corrections for Fe (Lind et al. 2012).”
Gaia FGK benchmark stars: Metallicity (2013, methodology): “The eff ct is typically larger for metal-poor and giant stars (Thévenin & Idiart 1999; Bergemann et al. 2012; Lind et al. 2012).”