Resolving the kinematics of the disks around Galactic B[e] supergiants

TL;DR

This study investigates the disk structures around Galactic B[e] supergiants by analyzing high-resolution spectra, revealing multiple rings with unique configurations and contrasting behaviors between binary and single stars.

Contribution

It provides detailed kinematic analysis of circumstellar disks, confirming multiple ring structures and their stability or variability in B[e] supergiants.

Findings

Disks consist of multiple rings with unique configurations.

Binaries show spectroscopic and photometric variability.

Single stars have stable ring structures.

Abstract

B[e] Supergiants are luminous evolved massive stars. The mass-loss during this phase creates a complex circumstellar environment with atomic, molecular, and dusty regions usually found in rings or disk-like structures. For a better comprehension of the mechanisms behind the formation of these rings, detailed knowledge about their structure and dynamics is essential. To address that, we obtained high-resolution optical and near-infrared spectra for 8 selected Galactic B[e] Supergiants, for which CO emission has been detected. Assuming Keplerian rotation for the disk, we combine the kinematics obtained from the CO bands in the near-IR with those obtained by fitting the forbidden emission [OI] $\lambda$5577, [OI] $\lambda\lambda$6300,6363, and [CaII] $\lambda\lambda$7291,7323 lines in the optical to probe the disk structure. We find that the emission originates from multiple ring structures around all B[e] Supergiants, with each one of them displaying a unique combination of rings regardless of whether the object is part of a binary system. The confirmed binaries display spectroscopic variations of their line intensities and profiles as well as photometric variability, whereas the ring structures around the single stars are stable.