Morphological classification of post-AGB stars

TL;DR

This study classifies the shapes of circumstellar shells around post-AGB stars using Hubble data, revealing diverse morphologies and correlations with galactic and infrared parameters.

Contribution

It provides the first comprehensive morphological classification of post-AGB stars based on high-resolution HST images, linking morphology with stellar and galactic properties.

Findings

40% stellar-like morphology

33% bipolar structures

12% multi-polar shapes

Abstract

We present a complete study of the morphology of post-Asymptotic Giant Branch (AGB) stars. Post-AGB is a very short evolutionary phase between the end of the AGB and the beginning of the Planetary Nebula (PN) stage (between 100 and 10,000 yrs). We have defined the end of the post-AGB phase and the beginning of the PN phase when the star is hot enough to fully ionize the hydrogen envelope. Post-AGB stars have a circumstellar shell that is illuminated by the central stars or partially ionized. However, this circumstellar shell is too small to be resolved from ground-based observations. Thus, we have used data from the Hubble Space Telescope (HST) database to resolve these shells. About 150 post-AGB were found in this database. Here we present the preliminary results on their morphological classification and the correlation with several parameters such as galactic latitude and IRAS fluxes. Our preliminary results show that 40% of the sample are stellar-like (S), 33 % bipolar (B), 12 % multi-polar (M) and 15 % elliptical (E).