Episodic post-shock dust formation in the colliding winds of Eta Carinae

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Eta Carinae shows broad peaks in near-infrared (IR) JHKL photometry, roughly correlated with times of periastron passage in the eccentric binary system. After correcting for secular changes attributed to reduced extinction from the thinning Homunculus nebula, these peaks have IR spectral energy distributions (SEDs) consistent with emission from hot dust at 1400-1700 K. The excess SEDs are clearly inconsistent, however, with the excess being entirely due to free-free wind or photospheric emission. One must conclude, therefore, that the broad near-IR peaks associated with Eta Carinae's 5.5 yr variability are due to thermal emission from hot dust. I propose that this transient hot dust results from episodic formation of grains within compressed post-shock zones of the colliding winds, analogous to the episodic dust formation in Wolf-Rayet (WR) binary systems like WR 140 or the post-shock dust formation seen in some supernovae like SN 2006jc. This dust formation in Eta Carinae seems to occur preferentially near and after periastron passage; near-IR excess emission then fades as the new dust disperses and cools. With the high grain temperatures and Eta Car's C-poor abundances, the grains are probably composed of corundum or similar species that condense at high temperatures, rather than silicates or graphite. Episodic dust formation in Eta Car's colliding winds significantly impacts our understanding of the system, and several observable consequences are discussed.

Original languageEnglish (US)
Pages (from-to)145-151
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Volume402
Issue number1
DOIs
StatePublished - Feb 2010
Externally publishedYes

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dust
shock
near infrared
wolves
spectral energy distribution
automobile
infrared photometry
corundum
eccentrics
thermal emission
nebulae
graphite
thinning
supernovae
energy
silicates
extinction
silicate
aluminum oxides
temperature

Keywords

  • Circumstellar matter
  • Dust, extinction
  • Stars: individual: Eta Carinae
  • Stars: variables: other
  • Stars: winds, outflows

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Episodic post-shock dust formation in the colliding winds of Eta Carinae. / Smith, Nathan.

In: Monthly Notices of the Royal Astronomical Society, Vol. 402, No. 1, 02.2010, p. 145-151.

Research output: Contribution to journalArticle

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