The circumstellar environments of NML Cygni and the cool hypergiants

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

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


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 H 2O vapor masers. We show that NML Cyg's circumstellar envelope is likely shaped by photodissociation 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 northeast/southwest orientation similar to that for its OH and H 2O masers, while VX Sgr is embedded in a spheroidal envelope. We find no evidence for circumstellar nebulosity around the intermediate-type hypergiants ρ Cas, HR 8752, and HR 5171 a, nor around the normal M-type supergiant μ Cep. We conclude that there is no evidence for high mass loss events prior to 500-1000 years ago for these four stars.

Original languageEnglish (US)
Pages (from-to)603-611
Number of pages9
JournalAstronomical Journal
Issue number1
StatePublished - Jan 2006


  • Stars: individual (ρ Cassiopeiae, NML Cygni, S Persei, VX Sagittarii)
  • Supergiants


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