Program: GS-2020B-Q-322

The post-main sequence evolution of massive stars give place to several phases with strong, often eruptive mass-loss events, including the enigmatic B[e] supergiants and yellow hypergiants. Stars in this group are surrounded by disks, which are cool and dense, and give rise to a complex chemistry, producing molecules and dust. Near infrared emission in CO bands has proven to be a major indicator for disk dynamics, as it originates typically from the inner edge of the molecular disk or ring. To better understand the mass-loss history in those objects, which is an essential ingredient for accurate predictions (e.g. of final stages) from stellar evolution calculations, a detailed study of their circumstellar material is crucial. We propose thus to use the IGRINS spectrograph to obtain high-resolution near IR spectra for a sample of B[e] supergiants and YHGs with confirmed CO emission, to model in detail the structure and kinematics of their circumstellar disks.