Radio and Infrared observations of Transition Objects

TL;DR

This study investigates the transition phase of stars evolving from post-AGB to planetary nebulae by combining radio and infrared observations to analyze ionization, chemistry, and dust properties in circumstellar envelopes.

Contribution

It introduces a multi-wavelength observational approach to characterize the physical and chemical changes during the transition from post-AGB stars to planetary nebulae, focusing on ionization and dust features.

Findings

Detection of free-free emission in about half of the targets.

Comparison of IR spectra reveals effects of ionization fronts on circumstellar chemistry.

Infrared data provide insights into dust extent and physical conditions.

Abstract

Observing objects in transition from pre- to young Planetary Nebula (PN), when the central star radiation starts to excite the envelope, can help us to understand the evolution of the circumstellar ejecta and their shaping mechanism/s. In our project we have selected a sample of hot post-AGB stars as Transition Phase candidates. Radio observations have led to detect free-free radiation from an ionized shell in about half of our targets, providing us with two sub-samples of ionized and non ionized Transition Objects. We are now using IRAC and IRS on the Spitzer Space Telescope to determine if extended emission is present (IRAC) and to study our targets' chemistry (IRS). In particular, by comparing spectra from the two sub-samples, the IRS observations will enable us to check how the presence of an ionization front effects the circumstellar envelope. The IRAC measurements, combined with previous ones in the literature, will give us information on the extent and physical conditions of the dust components.