Atmospheric parameter determination for massive stars via non-LTE spectrum analysis

TL;DR

This paper introduces a self-consistent non-LTE spectral analysis method that accurately determines atmospheric parameters of massive stars, reducing systematic errors and applicable across various stellar types.

Contribution

It presents a novel non-LTE spectrum analysis technique that significantly improves the precision of atmospheric parameter determination for massive stars.

Findings

Achieved ~1% uncertainty in effective temperature

Attained 0.05-0.10 dex accuracy in surface gravity

Demonstrated the method's applicability to OB and BA-type stars

Abstract

We describe a self-consistent spectrum analysis technique employing non-LTE line formation, which allows precise atmospheric parameters of massive stars to be derived: 1sigma-uncertainties as low as ~1% in effective temperature and ~0.05-0.10 dex in surface gravity can be achieved. Special emphasis is given to the minimisation of the main sources of systematic errors in the atmospheric model computation, the observed spectra and the quantitative spectral analysis. Examples of applications are discussed for OB-type stars near the main sequence and their evolved progeny, the BA-type supergiants, covering masses of ~8 to 25 Msun and a range in effective temperature from ~8000 to 35000 K. Relaxing the assumption of local thermodynamic equilibrium in stellar spectral synthesis has been shown to be decisive for improving the accuracy of quantitative analyses. Despite the present examples, which concentrate on hot, massive stars, the same philosophy can be applied to line-formation calculations for all types of stars, including cooler objects like the Sun, once the underlying stellar atmospheric physics is reproduced consistently.