The Circumstellar Environments of NML Cyg and the Cool Hypergiants

Michael T. Schuster; Roberta M. Humphreys; Massimo Marengo

doi:10.1086/498395

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The Circumstellar Environments of NML Cyg and the Cool Hypergiants

Michael T. Schuster·Roberta M. Humphreys·Massimo Marengo

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Abstract

We present high-resolution HST WFPC2 images of compact nebulosity surrounding the cool M-type hypergiants NML Cyg, VX Sgr and S Per. The powerful OH/IR source NML Cyg exhibits a peculiar bean-shaped asymmetric nebula that is coincident with the distribution of its H2O vapor masers. We show that NML Cyg's circumstellar envelope is likely shaped by photo-dissociation from the powerful, nearby association Cyg OB2 inside the Cygnus X superbubble. The OH/IR sources VX Sgr and S Per have marginally resolved envelopes. S Per's circumstellar nebula appears elongated in a NE/SW orientation similar to that for its OH and H2O masers, while VX Sgr is embedded in a spheroidal envelope. We find no evidence for circumstellar nebulosity around the intermediate-type hypergiants rho Cas, HR 8752, HR 5171a, nor the normal M-type supergiant mu Cep. We conclude that there is no evidence for high mass loss events prior to 500-1000 yrs ago for these four stars.

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Michael T. Schuster, Roberta M. Humphreys, Massimo Marengo. 2005-09-30. The Circumstellar Environments of NML Cyg and the Cool Hypergiants. https://doi.org/10.1086/498395

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