Discovery of multiple dust shells beyond 1 arcmin in the circumstellar envelope of IRC+10216 using Herschel/PACS

Abstract

We present new Herschel/PACS images at 70, 100, and 160 micron of the well-known, nearby, carbon-rich asymptotic giant branch star IRC+10216 revealing multiple dust shells in its circumstellar envelope. For the first time, dust shells (or arcs) are detected until 320 arcsec. The almost spherical shells are non-concentric and have an angular extent between 40 deg and 200 deg. The shells have a typical width of 5 arcsec - 8 arcsec, and the shell separation varies in the range of 10 arcsec - 35 arcsec, corresponding to 500-1700 yr. Local density variations within one arc are visible. The shell/intershell density contrast is typically 4, and the arcs contain some 50% more dust mass than the smooth envelope. The observed (nested) arcs record the mass-loss history over the past 16 000 yr, but Rayleigh-Taylor and Kelvin-Helmholtz instabilities in the turbulent astropause and astrosheath will erase any signature of the mass-loss history for at least the first 200 000 yr of mass loss. Accounting for the bowshock structure, the envelope mass around IRC+10216 contains >2Msun of gas and dust mass. It is argued that the origin of the shells is related to non-isotropic mass-loss events and clumpy dust formation.

8 pages, published in Astronomy & Astrophysics

References in corpus (22)

• Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy
• The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
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• HST Images Reveal Dramatic Changes in the Core of IRC+10216
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• Investigating Anomalous Photochemistry in the Inner Wind of IRC+10216 Through Interferometric Observations of HC${}_3$N
• Herschel/HIFI observation of highly excited rotational lines of HNC toward IRC +10 216
• Discovery of a Shell of Neutral Atomic Hydrogen Surrounding the Carbon Star IRC+10216
• Extended Dust Emission from Nearby Evolved Stars
• Surprising detection of an equatorial dust lane on the AGB star IRC+10216
• Connecting the evolution of thermally pulsing asymptotic giant branch stars to the chemistry in their circumstellar envelopes -- I. The case of hydrogen cyanide
• Large-scale environments of binary AGB stars probed by Herschel. II: Two companions interacting with the wind of pi1 Gruis
• Chemical tracers of a highly eccentric AGB-main sequence star binary
• Dusty OB stars in the Small Magellanic Cloud - II: Extragalactic Disks or Examples of the Pleiades Phenomenon?
• PACS and SPIRE range spectroscopy of cool, evolved stars
• Multi-epoch Optical Images of IRC+10216 Tell About the Central Star And the Adjacent Environment
• An Infrared Study of the Circumstellar Material Associated with the Carbon Star R Sculptoris
• Evidence for orbital motion of CW Leonis from ground-based astrometry
• [C I] and [C II] emission in the circumstellar envelope of IRC +10216 I. Observational data and NLTE modeling of the [C I] emission
• Near-infrared Integral-field Spectroscopy of the Wind Forming Region of CW Leo