Effect of NLTE model atmospheres on photometric amplitudes and phases of early B-type pulsating stars

TL;DR

This study investigates how non-local thermodynamic equilibrium (NLTE) stellar atmosphere models influence the theoretical photometric amplitudes and phases of early B-type pulsating stars, highlighting the importance of NLTE effects.

Contribution

It provides the first evaluation of NLTE effects on photometric observables of early B-type pulsators, including new tables of fluxes and limb-darkening coefficients for multiple passbands.

Findings

NLTE atmospheres significantly affect photometric amplitude ratios and phase differences.

The study offers publicly available tables of fluxes and limb-darkening coefficients for 12 passbands.

NLTE effects vary with chemical composition and opacities.

Abstract

We study all possible sources of inaccuracy in theoretical values of the photometric observables, i.e. amplitude ratios and phase differences, of early B-type main sequence pulsators. Here, we discuss effects of parameters coming from both models of stellar atmospheres and linear nonadiabatic theory of stellar pulsation. In particular, we evaluate for the first time the effect of the departure from the LTE approximation. The atmospheric input comes from line-blanketed, LTE and NLTE plane-parallel, hydrostatic models. To compute the limb-darkening coefficients for NLTE models, we use the Least-Square Method taking into account the accuracy of the flux conservation. We present effects of NLTE atmospheres, chemical composition and opacities on theoretical values of the photometric observables of early B-type pulsators. To this end, we compute tables with the passband fluxes, flux derivatives over effective temperature and gravity as well as the non-linear limb-darkening coefficients in 12 most often used passbands, i.e. in the Str\"omgern system, $uvby$, and in the Johnson-Cousins-Glass system, $UBVRIJHK$. We make these tables public available at the Wroc{\l}aw HELAS Web page, http://helas.astro.uni.wroc.pl.