Multiplicity of late-type B stars with HgMn peculiarity

TL;DR

This study investigates the multiplicity of late-type B stars with HgMn peculiarity, revealing a high prevalence of binary and multiple systems through near-infrared imaging, which may be crucial for understanding their chemical peculiarities.

Contribution

The paper provides the first extensive near-infrared imaging survey of HgMn stars, identifying numerous new companions and confirming high multiplicity rates.

Findings

High multiplicity fraction (~91%) among HgMn stars.

Detection of 33 new companion candidates.

Companions span a wide range of separations and magnitudes.

Abstract

Observations at various wavelengths of late B-type stars exhibiting strong overabundances of the chemical elements Hg and Mn in their atmospheres indicate that these stars are frequently found in binary and multiple systems. We intend to study the multiplicity of this type of chemically peculiar stars, looking for visual companions in the range of angular separation between 0.05" and 8". We carried out a survey of 56 stars using diffraction-limited near-infrared imaging with NAOS-CONICA at the VLT. Thirty-three companion candidates in 24 binaries, three triples, and one quadruple system were detected. Nine companion candidates were found for the first time in this study. Five objects are likely chance projections. The detected companion candidates have K magnitudes between 5.95m and 18.07m and angular separations ranging from <0.05" to 7.8", corresponding to linear projected separations of 13.5-1700 AU. Our study clearly confirms that HgMn stars are frequently members of binary and multiple systems. Taking into account companions found by other techniques, the multiplicity fraction in our sample may be as high as 91%. The membership in binary and multiple systems seems to be a key point to understanding the abundance patterns in these stars.