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

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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

Fingerprint

adaptive optics
diffraction
envelopes
dust
shell
carbon
interferometry
solar system
near infrared
asymptotic giant branch stars
spectroscopy
opacity
wavelength
continuums
stars
estimates
wavelengths
speed

Keywords

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

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

FOUR decades of IRC+10216 : Evolution of a carbon-rich dust shell resolved at 10 μm with MMT adaptive optics and MIRAC4. / Males, Jared R.; Close, Laird M; Skemer, Andrew J.; Hinz, Philip M; Hoffmann, William F.; Marengo, Massimo.

In: Astrophysical Journal, Vol. 744, No. 2, 133, 10.01.2012.

Research output: Contribution to journalArticle

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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.",
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