A mid-infrared imaging survey of post-AGB stars

Abstract

Abstract. Post-AGB stars are key objects for the study of the dramatic morphological changes of low-to intermediate-mass stars on their evolution from the Asymptotic Giant Branch (AGB) towards the planetary nebula stage. There is growing evidences that binary interaction processes may very well have a determining role in the shaping process of many objects, but so far direct evidence is still weak. We aim at a systematic study of the dust distribution around a large sample of post-AGB stars as a probe of the symmetry breaking in the nebulae around these systems. We used imaging in the mid-infrared to study the inner part of these evolved stars to probe direct emission from dusty structures in the core of post-AGB stars in order to better understand their shaping mechanisms. We imaged a sample of 93 evolved stars and nebulae in the mid-infrared using VISIR/VLT, T-Recs/Gemini South and Michelle/Gemini North. We found that all the the proto-planetary nebulae we resolved show a clear departure from spherical symmetry. 59 out of the 93 observed targets appear to be non resolved. The resolved targets can be divided in two categories. The nebulae with a dense central core, that are either bipolar and multipolar. The nebulae with no central core have an elliptical morphology. The dense central torus observed likely host binary systems which triggered fast outflows that shaped the nebulae.

On the central symmetry of the circumstellar envelope of RS Cnc

“…The question is of relevance to the late evolution of AGB stars that are known to commonly evolve into planetary nebulae having strongly asymmetric morphologies (for recent reviews, see e.g. Habing & Olofsson 2004;Herwig 2005;Marengo 2009;Bujarrabal 2010;Castro-Carrizo et al 2010;Pascoli & Lahoche 2010;Zhao-Geisler 2010;Amiri 2011;Geise 2011;Lagadec et al 2012 andBujarrabal et al 2013 andreferences therein).…”

Revealing the transition from post-AGB stars to planetary nebulae: non-thermal and thermal radio continuum observations

“…Ueta, Murakawa & Meixner 2007), Very Large Telescope (e.g. Lagadec et al 2007) and Very Long Baseline Array (e.g. Desmurs et al 2007).…”