Spectroscopic diagnostics for circumstellar disks of B[e] supergiants

TL;DR

This paper discusses spectroscopic methods to analyze the circumstellar disks of B[e] supergiants, revealing that their material is arranged in multiple rings on stable orbits, challenging existing formation theories.

Contribution

It provides new observational evidence that circumstellar material forms multiple Keplerian rings, suggesting pulsations may influence disk formation in B[e] supergiants.

Findings

Circumstellar material is in multiple rings on stable Keplerian orbits.

Current theories struggle to explain the ring formation.

Pulsations might play a key role in disk formation.

Abstract

B[e] supergiants (B[e]SGs) are emission-line objects, presumably in a short-lived phase in the post-main sequence evolution of massive stars. Their intense infrared excess emission indicates large amounts of warm circumstellar dust, and the stars were longtime assumed to possess an aspherical wind consisting of a classical line-driven wind in polar direction and a dense, slow equatorial wind dubbed outflowing disk. The general properties obtained for these disks are in line with this scenario, although current theories have considerable difficulties reproducing the observed quantities. Therefore, more sophisticated observational constraints are needed. These follow from combined optical and infrared spectroscopic studies, which delivered the surprising result that the circumstellar material of B[e]SGs is concentrated in multiple rings revolving the stars on stable Keplerian orbits. Such a scenario requires new ideas for the formation mechanism, in which pulsations might play an important role.