Magnetic properties of three cool CP stars with strong fields

TL;DR

This paper investigates the magnetic properties of three cool chemically peculiar stars, revealing strong magnetic fields and periodic variations, and suggests possible rapid oscillations in two binary components.

Contribution

It provides new long-term spectroscopic data and analysis of magnetic fields in cool CP stars, including a revised rotation period and magnetic field measurements in a binary system.

Findings

Surface magnetic field of HD 178892 varies from 17 to 23 kG.

Binary components of BD +40°175 have magnetic fields of 14 kG and 9-11 kG.

Possible rapid oscillation (roAp) nature of the binary components is suggested.

Abstract

The study of magnetic fields of cool chemically peculiar stars with effective temperatures less than 10 000 K is very important to understand the nature of their magnetism. We present new results of a long-term spectroscopic monitoring of the well-known magnetic star HD 178892. The analysis of spectra taken with the Russian 6-m telescope has revealed a periodic variation of the surface magnetic field from 17 to 23 kG. A revised rotational period of HD 178892 was extracted from the mean longitudinal field: 8.2549 days. We have continued the study of the components of the magnetic binary BD +40^{\circ}175 started by V. Elkin at SAO RAS. Our measurements of magnetically splitted lines in the spectra of each component show the presence of strong magnetic fields in both components. The surface field in the case of the component A was about 14 kG at three different epochs. The component B possesses a slightly weaker field: B_{s} varies from 9 to 11 kG. A preliminary analysis of the chemical abundances allows us to make an assumption about the roAp nature of both components of BD +40^{\circ}175.