Theoretical analysis of the atmospheres of CP stars. Effects of the individual abundance patterns

TL;DR

This paper provides a theoretical analysis of the atmospheres of chemically peculiar stars, emphasizing the importance of considering individual element abundance patterns to improve model accuracy and reduce analysis errors.

Contribution

It introduces a homogeneous study of CP star atmospheres, highlighting the influence of specific elements and validating the use of tailored models over scaled solar abundances.

Findings

Si, Cr, and Fe significantly influence CP star atmospheres.

The Delta_a photometric system reliably detects Fe peculiarities.

Uncertainty in abundance analysis is less than ±0.25 dex with tailored models.

Abstract

Context. See abstract in the paper. Aims. See abstract in the paper. Methods. See abstract in the paper. Results. We present a homogeneous study of model atmosphere temperature structure, energy distribution, photometric indices in the uvbybeta and Delta_a systems, hydrogen line profiles, and the abundance determination procedure as it applies to CP stars. In particular, we found that Si, Cr and Fe are the main elements to influence model atmospheres of CP stars, and thus to be considered in order to assess the adequacy of model atmospheres with scaled solar abundances in application to CP stars. We provide a theoretical explanation of the robust property of the Delta_a photometric system to recognize CP stars with peculiar Fe content. Also, the results of our numerical tests using model atmospheres with one or several elements overabundant (Si and Fe by +1 dex, Cr by +2 dex) suggest that the uncertainty of abundance analysis in the atmospheres of CP stars using models with scaled abundances is less than plus/minus 0.25 dex. If the same homogeneous models are used for the abundance stratification analysis then we find that the uncertainty of the value of the vertical abundance gradient is within an 0.4 dex error bar. Conclusions. Model atmospheres with individual abundance patterns should be used in order to match the actual anomalies of CP stars and minimize analysis errors.