FOUR decades of IRC+10216: Evolution of a carbon-rich dust shell resolved at 10 μm with MMT adaptive optics and MIRAC4

Jared R. Males, Laird M. Close, Andrew J. Skemer, Philip M. Hinz, William F. Hoffmann, Massimo Marengo

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

The evolved carbon-rich asymptotic giant branch star IRC+10216 (CW Leo) is the brightest mid-infrared source outside the solar system, as well as one of the closest examples of an evolved star losing mass. It has a complex and variable circumstellar structure on small scales in the near-infrared, and mid-infrared interferometry has revealed a dynamic dust formation zone. We have obtained diffraction-limited imaging and grism spectroscopy of IRC+10216 at the 6.5m MMT in the N band (∼8-13 μm). These new observations show that a change has occurred in the dust shell surrounding IRC+10216 over the last two decades, which is illustrated by a change in the apparent shape of the well-known SiC spectral feature at ∼11 μm and a reduction in the continuum at 13 μm. As expected, our diffraction-limited spatial information shows an extended circumstellar envelope. We also demonstrate that the dusty envelope appears to be ∼30% larger at the wavelengths of the SiC feature, likely due to the increased opacity of SiC. The deconvolved full width at half-maximum of the object increases from 043 (∼56AU) for λ < 10 μm to 058 (∼75AU) at 11.8 μm, then decreases to 05 (∼65AU) at 12.7 μm. Our estimates of IRC+10216's size allow us to plausibly tie the change in the spectrum over the last 12.5 years to the evolution of the dusty circumstellar envelope at speeds of 12-17kms-1.

Original languageEnglish (US)
Article number133
JournalAstrophysical Journal
Volume744
Issue number2
DOIs
StatePublished - Jan 10 2012

Keywords

  • instrumentation: adaptive optics
  • stars: AGB and post-AGB
  • stars: carbon

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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