Intermediate-Mass Mergers: A New Scenario for Several FS CMa Stars

TL;DR

This paper discusses FS CMa stars, a peculiar B-type star group with emission lines and infrared excess, proposing a merger hypothesis as a recent explanation for their properties.

Contribution

It introduces the merger hypothesis as a new explanation for the origin and nature of FS CMa stars, supported by recent evidence.

Findings

Evidence supports the merger hypothesis for FS CMa stars.

FS CMa stars exhibit extended circumstellar gas and dust.

The merger scenario explains the peculiar spectral features.

Abstract

We summarise the properties and nature of a peculiar group of B-type stars called FS CMa stars. These stars show the B[e] phenomenon, i.e., their spectra exhibit both forbidden emission lines and infrared excess. Such properties point to an extended circumstellar gas and dust component. Although the phenomenon has been explained in most B[e] stars, the origin and nature of FS CMa stars is disputed. Here, we focus on the merger hypothesis, for which evidence has recently been discovered.