Non-LTE line formation for \ion{Mg}{I/II}: Abundances and stellar parameters. Model atom and first results on A-type stars

Details Non-LTE line formation for \ion{Mg}{I/II}: Abundances and stellar parameters. Model atom and first results on A-type stars Non-LTE line formation for \ion{Mg}{I/II}: Abundances and stellar parameters. Model atom and first results on A-type stars

Apr 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001a%26a...369.1009p&link_type=abstract

Astronomy and Astrophysics, v.369, p.1009-1026 (2001)

Astronomy and Astrophysics

Astrophysics

59

Atomic Data, Line: Formation, Stars: Abundances, Fundamental Parameters, Supergiants

Scientific paper

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 (A0 V), eta Leo (A0 Ib) and HD 92207 (A0 Iae) using high S/N and high resolution spectra at visual and near-IR wavelengths. The ionization equilibrium of \ion{Mg}{i/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 (T_effla \ 8000 K) 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 \ion{Mg}{i/ii} lines in the observations are reproduced simultaneously by the calculated line profiles with high ccuracy. For Vega spectral synthesis in the UV region of the \ion{Mg}{i/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 Mg I - typically la 0.3 dex - even in supergiants, but are essential for an accurate effective temperature determination. From the Mg Ii spectrum, only the features at lambda lambda 4481 and 7877-96 Å 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. Based on observations collected at the European Southern Observatory, La Silla, Chile (ESO No 62.H-0176).

Affiliated with

Also associated with

No associations

Rating

Non-LTE line formation for \ion{Mg}{I/II}: Abundances and stellar parameters. Model atom and first results on A-type stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Non-LTE line formation for \ion{Mg}{I/II}: Abundances and stellar parameters. Model atom and first results on A-type stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-LTE line formation for \ion{Mg}{I/II}: Abundances and stellar parameters. Model atom and first results on A-type stars will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1181827