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M.T. Schuster, R.M. Humphreys (University of Minnesota)
The cool hypergiants are evolved massive stars that lie just below the empirical upper luminosity boundary in the HR Diagram, with spectral types ranging from late A to M. Recent observations of two of these stars (IRC +10420 and VY CMa) have yielded surprising results about their circumstellar environments including evidence for bi-polarity, equatorial disks, and multiple high mass loss events. To better understand their mass loss histories, we obtained high resolution WF/PC2 PC images of 7 of the most luminous known cool stars to sample a variety of stages during their brief evolution as cool hypergiants. the presence or lack of fossil shells, equatorial ejecta, jets and other structures in their circumstellar environments is a record of their current and prior mass loss episodes. NML Cyg, Rho Cas, Mu Cep, VX Sgr, S Per, HR 8752, and HR 5171A were selected on the basis of their infrared emission, strong molecular emission, or peculiar spectroscopic variations to give us a snapshot of different steps in their evolution across the top of the HR Diagram. We have also imaged these same stars in the near and mid-infrared. We present evidence for extensive circumstellar material and discuss the implications for their evolutionary state.
The author(s) of this abstract have provided an email address for comments about the abstract: hercu@astro.umn.edu