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Astron. Astrophys. 359, 707-715 (2000)

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Multiple shells in IRC+10216: shell properties *

N. Mauron 1 and P.J. Huggins 2

1 Groupe d'Astrophysique, CNRS and Université de Montpellier, Case 072, Place Bataillon, 34095 Montpellier Cedex 05, France
2 Physics Department, New York University, 4 Washington Place, New York, NY 10003, USA

Received 22 March 2000 / Accepted 26 April 2000


We report on the properties of the multiple shells in the circumstellar envelope of IRC+10216, using deep optical imaging, including data from the Hubble Space Telescope. The intensity profiles confirm the presence of thin ([FORMULA]-3"), limb-brightened shells in the envelope, seen in stellar and ambient Galactic light scattered by dust. The shells are spaced at irregular intervals of [FORMULA]-20", corresponding to time scales of 200-800 yr, although intervals as short as [FORMULA] (40 yr) are seen close to the star. The location of the main shells shows a good correlation with high-resolution, molecular line maps of the inner envelope, indicating that the dust and gas are well coupled. The shell/intershell density contrast is typically [FORMULA], and we find that the shells form the dominant mass component of the circumstellar envelope. The shells exhibit important evolutionary effects: the thickness increases with increasing radius, with an effective dispersion velocity of 0.7 km s-1 and there is evidence for shell interactions. Despite the presence of bipolar structure close to the star, the global shell pattern favors a roughly isotropic, episodic mass loss mechanism, with a range of time scales.

Key words: stars: AGB and post-AGB – stars: mass-loss – stars: individual: IRC +10216 – stars: circumstellar matter

* Based on observations made with the Canada-France-Hawaii telescope, operated by CNRS, NRCC and UH, and on dearchived observations made with the NASA/ESA Hubble Space Telescope, operated by AURA Inc., under NASA contract NAS5-26555

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© European Southern Observatory (ESO) 2000

Online publication: July 7, 2000