2001A&A...369.1009P


C.D.S. - SIMBAD4 rel 1.7 - 2019.09.23CEST03:48:07

2001A&A...369.1009P - Astronomy and Astrophysics, volume 369, 1009-1026 (2001/4-3)

Non-LTE line formation for MgI/II: Abundances and stellar parameters. Model atom and first results on A-type stars.

PRZYBILLA N., BUTLER K., BECKER S.R. and KUDRITZKI R.P.

Abstract (from CDS):

An extensive model atom for non-LTE line-formation calculations for neutral and singly-ionized magnesium is presented, taking into account recent improvements in the atomic data. As a test and first application of the model, stellar parameters and magnesium abundances are determined on the basis of line-blanketed LTE model atmospheres for three stars: Vega (A0V), η Leo (A0Ib) and HD 92207 (A0Iae) using high S/N and high resolution spectra at visual and near-IR wavelengths. The ionization equilibrium of MgI/II proves to be a sensible temperature indicator for early A-type stars at all luminosities. Evidence is given that in late A and early F-type supergiants (Teff≲8000K) the determination of accurate stellar parameters is hampered by the presence of a pressure inversion region in the model atmospheres at line-formation depths. The MgI/II lines in the observations are reproduced simultaneously by the calculated line profiles with high accuracy. For Vega spectral synthesis in the UV region of the MgI/II resonance lines also proves excellent consistency with the results from the visual. The dependence of the non-LTE effects on the atmospheric parameters is discussed with special emphasis on the supergiants where a strong radiation field at low particle densities favours deviations from LTE, especially in the minor ionic species of neutral magnesium. Non-LTE corrections turn out to be small in MgI - typically ≲0.3dex - even in supergiants, but are essential for an accurate effective temperature determination. From the MgII spectrum, only the features at λλ 4481 and 7877-96Å react sensitively to non-LTE effects. Furthermore, the influence of microturbulence on the statistical-equilibrium calculations is investigated. The line strengths are found to be systematically affected.

Abstract Copyright:

Journal keyword(s): atomic data - line: formation - stars: abundances, fundamental parameters, supergiants

Simbad objects: 6

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Number of rows : 6

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 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 10526 1
2 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9042 1
3 * eta Leo * 10 07 19.9518606 +16 45 45.580270 3.17 3.39 3.41 3.32 3.35 A0Ib 312 1
4 HD 92207 sg* 10 37 27.0681943657 -58 44 00.015326487 5.71 5.95 5.45     A0Ia 144 0
5 * alf Lyr dS* 18 36 56.33635 +38 47 01.2802 0.03 0.03 0.03 0.07 0.10 A0Va 2467 0
6 NGC 6822 G 19 44 56.199 -14 47 51.29   18 8.1     ~ 1402 0

    Equat.    Gal    SGal    Ecl

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2019.09.23-03:48:07

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