Title: Hypergiant Twins: Chemistry and structure of NML Cyg and VY Cma

Abstract: Extreme supergiant stars, or hypergiants, experience substantial, sporadic mass loss events that form complex envelope structures composed of arcs, clumps, and knots. The uniformity and regularity of mass loss also significantly modify evolutionary time scales and affects the geometry of the resulting envelope. The red hypergiants NML Cyg and VY CMa are the best examples of these types of stars. Here, I'll be presenting the spectral line survey of NML Cyg and VY CMa where emission spectra of molecules such as SO2, SO, and CO show evidence of complex morphology resulting from this sporadic mass loss. I will also share preliminary data from our recent ALMA observation of VY CMa at Band 6 (1 mm) where, with the 0.25-arcsecond resolution, we are creating the image of the envelope of VY CMa in multiple molecular lines. While some observations are still in progress, preliminary maps of SO, SiO, SO2, and PO have been obtained. In particular, SO and SO2 emission appears to trace the striking morphology seen in the dust image of VY CMa, including the Arc 1, the NW Arc, among other features. PO, in contrast, is more confined to the inner envelope close to the star. These images will be presented, as well as other new data, and the implications for the evolution of massive stars will be discussed.