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J/A+A/615/A139      3D non-LTE Balmer line formation             (Amarsi+, 2018)

Effective temperature determinations of late-type stars based on 3D non-LTE Balmer line formation. Amarsi A.M., Nordlander T., Barklem P.S., Asplund M., Collet R., Lind K. <Astron. Astrophys. 615, A139 (2018)> =2018A&A...615A.139A (SIMBAD/NED BibCode)
ADC_Keywords: Models, atmosphere ; Line Profiles ; Effective temperatures ; Stars, late-type Keywords: radiative transfer - line: formation - line: profiles - stars: atmospheres - stars: late-type Abstract: Hydrogen Balmer lines are commonly used as spectroscopic effective temperature diagnostics of late-type stars. However, reliable inferences require accurate model spectra, and the absolute accuracy of classical methods that are based on one-dimensional (1D) hydrostatic model atmospheres and local thermodynamic equilibrium (LTE) is still unclear. To investigate this, we carry out 3D non-LTE calculations for the Balmer lines, performed, for the first time, over an extensive grid of 3D hydrodynamic STAGGER model atmospheres. For Hα, Hβ, and Hγ we find significant 1D non-LTE versus 3D non-LTE differences (3D effects): the outer wings tend to be stronger in 3D models, particularly for Hγ, while the inner wings can be weaker in 3D models, particularly for Hα. For Hα, we also find significant 3D LTE versus 3D non-LTE differences (non-LTE effects): in warmer stars (Teff≈6500K) the inner wings tend to be weaker in non-LTE models, while at lower effective temperatures (Teff≈4500K) the inner wings can be stronger in non-LTE models; the non-LTE effects are more severe at lower metallicities. We test our 3D non-LTE models against observations of well-studied benchmark stars. For the Sun, we infer concordant effective temperatures from Hα, Hβ, and Hγ; however the value is too low by around 50K which could signal residual modelling shortcomings. For other benchmark stars, our 3D non-LTE models generally reproduce the effective temperatures to within 1σ uncertainties. For Hα, the absolute 3D effects and non-LTE effects can separately reach around 100K, in terms of inferred effective temperatures. For metal-poor turn-off stars, 1D LTE models of Hα can underestimate effective temperatures by around 150K. Our 3D non-LTE model spectra are publicly available, and can be used for more reliable spectroscopic effective temperature determinations. Description: File lineprof.txt: contains emergent total (I) and continuum (Ic) intensities at specific wavelengths (wl, or wl_air) and viewing angles (mu), the latter with weights (wmu), for the model atmospheres with different effective temperatures (Teff), surface gravities (lgg), and iron abundance ratios ([Fe/H]). If rotational broadening and instrumental broadening are to be neglected, the normalised flux can be obtained via Sum(I * mu * wmu) / Sum(Ic * mu * wmu), at a given wavelength and for a given model atmosphere. File flux_3d.fits: contains a regular grid of normalised fluxes constructed by interpolation/extrapolation of the data in lineprof.txt. The fluxes are given for different effective temperatures (Teff), surface gravities (lgg), iron abundance ratios ([Fe/H]), projected rotational velocity (vsini), Gaussian instrumental profile velocity widths (vbroad), vacuum wavelengths (wl), and lines. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file lineprof.dat 99 309270 Raw line profiles flux_3d.fits 2880 666670 Regular grid of line profiles
Byte-by-byte Description of file: lineprof.dat
Bytes Format Units Label Explanations
1- 5 I5 K Teff Effective temperature 7- 10 F4.2 [cm/s2] logg Base 10 logarithm of surface gravity 12- 16 F5.2 --- [Fe/H] Iron abundance 18- 31 E14.8 Hz nu Frequency 34- 42 F9.5 nm wl Vacuum wavelength 45- 53 F9.5 nm wlair Air wavelength 55- 61 F7.5 --- mu Viewing angle 63- 69 F7.5 --- wmu Viewing angle weight 71- 84 E14.8 W/m/Hz Ic Continuum intensity 86- 99 E14.8 W/m/Hz I Intensity
Acknowledgements: Anish Mayur Amarsi, amarsi(at)
(End) Patricia Vannier [CDS] 14-Jun-2018
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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