B[e] Supergiants' circumstellar environment: disks or rings?

TL;DR

This study investigates the circumstellar environments of B[e] Supergiants, revealing that their emission features originate from one or multiple rings, enhancing understanding of their complex mass-loss structures.

Contribution

It provides the first homogeneous high-resolution spectral analysis of B[e] Supergiants, demonstrating that their emission lines originate from rings or disks, clarifying their circumstellar structure.

Findings

Emission lines form in rings or disks.

Multiple rings are present around some stars.

Spectral data supports ring/disk formation models.

Abstract

B[e] Supergiants are a phase in the evolution of some massive stars for which we have observational evidence but no predictions by any stellar evolution model. The mass-loss during this phase creates a complex circumstellar environment with atomic, molecular, and dust regions usually found in rings or disk-like structures. However, the detailed structure and the formation of the circumstellar environment are not well-understood, requiring further investigation. To address that we initiated an observing campaign to obtain a homogeneous set of high-resolution spectra in both the optical and NIR (using MPG-ESO/FEROS, GEMINI/Phoenix and VLT/CRIRES, respectively). We monitor a number of Galactic B[e] Supergiants, for which we examined the [OI] and [CaII] emission lines and the bandheads of the CO and SiO molecules to probe the structure and the kinematics of their formation regions. We find that the emission from each tracer forms either in a single or in multiple equatorial rings.