Similarities in the structure of the circumstellar environments of B[e] supergiants and yellow hypergiants

TL;DR

This study compares the circumstellar environments of B[e] supergiants and yellow hypergiants, revealing shared features like disk-like structures and similar emission lines, suggesting analogous mass-loss processes.

Contribution

It identifies common spectral tracers and structural features in B[e]SGs and YHGs, highlighting their similar circumstellar geometries despite different evolutionary stages.

Findings

Shared [O I] and [Ca II] emission lines in both star types.

Evidence of disk or ring structures around YHGs similar to B[e]SGs.

Kinematic analysis suggests Keplerian disks in some YHGs.

Abstract

Yellow Hypergiants (YHGs) and B[e] supergiants (B[e]SGs), though in different phases in their evolution, display many features in common. This is partly due to the fact that both types of objects undergo strong, often asymmetric mass loss, and the ejected material accumulates in shells, rings, or disk-like structures, giving rise to emission from warm molecules and dust. We performed an optical spectroscopic survey of northern Galactic emission-line stars aimed at identifying tracers for the structure and kinematics of circumstellar environments. We identified two sets of lines, [O I] and [Ca II], which originate from the discs of B[e]SGs. The same set of lines is observed in V1302 Aql and V509 Cas, which are both hot YHGs. While V1302 Aql is known to have a disc-like structure, the kinematical broadening of the lines in V509 Cas suggest a Keplerian disk or ring around this star alike their hotter B[e]SG counterparts.