The [O III] veil: Astropause of η Carinae's wind?

Nathan Smith, Jon A. Morse, John Bally

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

We present narrowband images of η Carinae in the light of [O III] λ5007 obtained with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2, as well as a ground-based image in the same emission line with a larger field of view. These images show a thin veil of [O III] emission around η Car and its ejecta, confirming the existence of an oxygen-bearing "cocoon" inferred from spectra. This [O III] veil may be the remnant of the preoutburst wind of η Car, and its outer edge probably marks the interface where η Car's ejecta meet the stellar wind of the nearby O4 V((f)) star HD 303308 or other ambient material in the Carina Nebula; i.e., it marks the "astropause" in η Car's wind. This veil is part of a more extensive [O III] shell that appears to be shaped and ionized by HD 303308. A pair of HST images with a 10 yr baseline shows no significant proper motion, limiting the expansion speed away from η Car to 12 ± 13 km s -1, or an expansion age of a few times 10 4 yr. Thus, this is probably the decelerated preoutburst luminous blue variable wind of 77 Car. The [O III] morphology is very different from that seen in [N II], which traces younger dense knots of CNO-processed material; this represents a dramatic shift in the chemical makeup of material recently ejected by η Car. This change in the chemical abundances of the ejecta may have resulted from the sudden removal of the star's outer envelope during η Car's 19th century outburst or an earlier but similar event.

Original languageEnglish (US)
Pages (from-to)1778-1783
Number of pages6
JournalAstronomical Journal
Volume130
Issue number4
DOIs
Publication statusPublished - Oct 2005
Externally publishedYes

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Keywords

  • Circumstellar matter
  • H II regions
  • ISM: bubbles
  • Stars: individual (Eta Carinae)
  • Stars: winds, outflows

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

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