Spectral analysis of Kepler SPB and Beta Cep candidate stars

TL;DR

This study analyzes Kepler-observed candidate SPB and Beta Cep stars by determining their fundamental parameters through spectral and photometric methods, identifying pulsation types and elemental peculiarities.

Contribution

It provides a detailed spectroscopic analysis of 14 candidate stars, comparing LTE and NLTE effects, and classifies their pulsation types and chemical peculiarities.

Findings

No significant NLTE effects on the results.

Deviations in Teff compared to Kepler Input Catalogue.

Identification of potential hybrid and pure pulsators.

Abstract

We determine the fundamental parameters of SPB and Beta Cep candidate stars observed by the Kepler satellite mission and estimate the expected types of non-radial pulsators by comparing newly obtained high-resolution spectra with synthetic spectra computed on a grid of stellar parameters assuming LTE and check for NLTE effects for the hottest stars. For comparison, we determine Teff independently from fitting the spectral energy distribution of the stars obtained from the available photometry. We determine Teff, log(g), micro-turbulent velocity, vsin(i), metallicity, and elemental abundance for 14 of the 16 candidate stars, two of the stars are spectroscopic binaries. No significant influence of NLTE effects on the results could be found. For hot stars, we find systematic deviations of the determined effective temperatures from those given in the Kepler Input Catalogue. The deviations are confirmed by the results obtained from ground-based photometry. Five stars show reduced metallicity, two stars are He-strong, one is He-weak, and one is Si-strong. Two of the stars could be Beta Cep/SPB hybrid pulsators, four SPB pulsators, and five more stars are located close to the borders of the SPB instability region.