Probing the ejecta of evolved massive stars in transition: A VLT/SINFONI K -band survey

Massive evolved stars in the transition phases, such as luminous blue variables(LBVs), B[e] supergiants(B[e]SGs), and yellow hypergiants (YHGs), are not well understood, and yet crucial steps in determining accurate stellar and galactic evolution models. The circumstellar environments of these stars reveal their mass-loss history) identifying clues to both their individual evolutionary status and the connection between objects of different phases. Here we present a survey of 25 such evolved massive stars (16 E[e]SGs, 6 LEVs, 2 YHGs, and l Peculiar Oe star), observed in the K-band and the Spectrograph for integral Field Observation in the Near-Infrared on the ESO VLT UT4 8 m telescope. The lack of CO features in several high luminosity B[e]SGs and variability in others suggests that they may in fact be LBV candidates, strengthening the connection between these two very similar transition phases.