1 research outputs found
Bipolar outflow on the Asymptotic Giant Branch - the case of IRC+10011
Near-IR imaging of the AGB star IRC+10011 (= CIT3) reveals the presence of a
bipolar structure within the central ~0.1 arcsec of a spherical dusty wind. We
show that the image asymmetries originate from ~1E-4 Msun of swept-up wind
material in an elongated cocoon whose expansion is driven by bipolar jets. We
perform detailed 2D radiative transfer calculations with the cocoon modeled as
two cones extending to ~1,100 AU within an opening angle of ~30deg, imbedded in
a wind with the standard r^{-2} density profile. The cocoon expansion started
<~200 years ago, while the total lifetime of the circumstellar shell is ~5,500
years. Similar bipolar expansion, at various stages of evolution, has been
recently observed in a number of other AGB stars, culminating in jet breakout
from the confining spherical wind. The bipolar outflow is triggered at a late
stage in the evolution of AGB winds, and IRC+10011 provides its earliest
example thus far. These new developments enable us to identify the first
instance of symmetry breaking in the evolution from AGB to planetary nebula.Comment: accepted for publication in MNRAS, high-resolution pdf version can be
found at http://www.leluya.org/downloads/Vinkovic_et_al_IRC+10011.pd