Spectroscopic variability and magnetic fields of HgMn stars

TL;DR

This paper investigates the spectroscopic variability and magnetic fields of HgMn stars, revealing common surface inhomogeneities, diverse chemical peculiarities, and magnetic field characteristics, which enhance understanding of star formation and chemical anomalies in binary systems.

Contribution

It provides new observational evidence of surface inhomogeneities and magnetic fields in HgMn stars, linking chemical peculiarities with magnetic phenomena and binary star characteristics.

Findings

Most HgMn stars show spectral variability indicating surface inhomogeneities.

All components in studied systems are chemically peculiar with distinct abundance patterns.

Magnetic fields are present in HgMn stars, affecting spectral line intensities through Zeeman effects.

Abstract

The discovery of exotic abundances, chemical inhomogeneities, and weak magnetic fields on the surface of late B-type primaries in spectroscopic binaries has important implications not only for our understanding of the formation mechanisms of stars with Hg and Mn peculiarities themselves, but also for the general understanding of B-type star formation in binary systems. The origin of the abundance anomalies observed in late B-type stars with HgMn peculiarity is still poorly understood. The connection between HgMn peculiarity and membership in binary and multiple systems is supported by our observations during the last decade. The important result achieved in our studies of a large sample of HgMn stars is the finding that most HgMn stars exhibit spectral variability of various chemical elements, proving that the presence of an inhomogeneous distribution on the surface of these stars is a rather common characteristic and not a rare phenomenon. Further, in the studied systems, we found that all components are chemically peculiar with different abundance patterns. Generally, He and Si variable Bp stars possess large-scale organised magnetic fields that in many cases appear to occur essentially in the form of a single large dipole located close to the centre of the star. The presence of magnetic fields in the atmospheres of HgMn stars has been demonstrated in several studies. In addition to the measurements of longitudinal and quadratic magnetic fields, this work also showed evidence for a relative magnetic intensification of Fe II lines produced by different magnetic desaturations induced by different Zeeman-split components.