IRC+10 degrees 216 mass loss properties through the study of lambda 3 mm emission
Journal article, 2019

Low-mass evolved stars are major contributors to interstellar medium enrichment as a consequence of the intense mass-loss process these stars experience at the end of their lives. The study of the gas in the envelopes surrounding asymptotic giant branch (AGB) stars through observations in the millimetre wavelength range provides information about the history and nature of these molecular factories. Here we present ALMA observations at subarsecond resolution, complemented with IRAM-30 m data, of several lines of SiO, SiS, and CS towards the best-studied AGB circumstellar envelope, IRC + 10 degrees 216. We aim to characterise their spatial distribution and determine their fractional abundances mainly through radiative transfer and chemical modelling. The three species display extended emission with several enhanced emission shells. CS displays the most extended distribution reaching distances up to approximately 20 ''. SiS and SiO emission have similar sizes of approximately 11 '', but SiS emission is slightly more compact. We have estimated fractional abundances relative to H-2, which on average are equal to f(SiO) similar to 10(-7), f(SiS) similar to 10(-6), and f(CS) similar to 10(-6) up to the photo-dissociation region. The observations and analysis presented here show evidence that the circumstellar material displays clear deviations from an homogeneous spherical wind, with clumps and low density shells that may allow UV photons from the interstellar medium (ISM) to penetrate deep into the envelope, shifting the photo-dissociation radius inwards. Our chemical model predicts photo-dissociation radii compatible with those derived from the observations, although it is unable to predict abundance variations from the starting radius of the calculations (similar to 10 R-*), which may reflect the simplicity of the model. We conclude that the spatial distribution of the gas proves the episodic and variable nature of the mass loss mechanism of IRC + 10 degrees 216, on timescales of hundreds of years.

circumstellar matter

stars: individual: IRC+10216

stars: AGB and post-AGB


Luis Velilla Prieto

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

J. Cernicharo

Spanish National Research Council (CSIC)

M. Agundez

Spanish National Research Council (CSIC)

J. P. Fonfria

Spanish National Research Council (CSIC)

G. Quintana-Lacaci

Spanish National Research Council (CSIC)

N. Marcelino

Spanish National Research Council (CSIC)

A. Castro-Carrizo

Institut de Radioastronomie Millimétrique (IRAM)

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 629 A146

Subject Categories

Astronomy, Astrophysics and Cosmology



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