Chemically peculiar stars and their temperature calibration

TL;DR

This paper investigates the effective temperature calibration of chemically peculiar stars using photometry, providing new correction methods and relations for various subgroups and photometric systems.

Contribution

It offers updated temperature calibration corrections for CP stars, including He (CP4) objects, and introduces new relations for bolometric correction and interstellar reddening estimation.

Findings

He (CP4) stars require significant temperature correction.

New bolometric correction relation for CP stars.

Standard calibrations can estimate interstellar reddening for magnetic CP stars.

Abstract

The determination of effective temperature for chemically peculiar (CP) stars by means of photometry is a sophisticated task due to their abnormal colours. Standard calibrations for normal stars lead to erroneous results and, in most cases corrections are necessary. In order to specify appropriate corrections, direct temperature determinations for 176 objects of the different subgroups were collected from the literature. This much larger sample than in previous studies therefore allows a more accurate investigation, mostly based on average temperatures. For the three main photometric systems (UBV, Geneva, Stromgren uvbybeta), methods to determine effective temperature are presented together with a comparison with former results. Based on the compiled data we provide evidence that He (CP4) objects also need a considerable correction, not noticed in former investigations due to their small number. Additionally, a new relation for the bolometric correction and the capability of standard calibrations to deduce interstellar reddening for magnetic CP stars are shown.