An Infrared Photometric and Spectroscopic Study of Post-AGB Stars

TL;DR

This study analyzes mid-infrared spectra and spectral energy distributions of post-AGB stars, revealing spectral features, evolutionary indicators, and the first detection of fullerene vibrations in such stars.

Contribution

It provides new insights into the spectral features, mass loss rates, and the first detection of fullerene vibrations in post-AGB stars using Spitzer data.

Findings

Detection of PAHs and silicates in emission in most sources

Correlation between PAH features and stellar parameters

First identification of fullerene (C60) IR modes in a PAGB star

Abstract

We present here $Spitzer$ mid-infrared (IR) spectra and modeling of the spectral energy distribution (SED) of a selection of post-Asymptotic Giant Branch (PAGB) stars. The mid-IR spectra of majority of these sources showed spectral features such as polycyclic aromatic hydrocarbons (PAHs) and silicates in emission. Our results from SED modeling showed interesting trends of dependency between the photospheric and circumstellar parameters. A trend of dependency is also noticed between the ratios of equivalent widths (EWs) of various vibrational modes of PAHs and the photospheric temperature T$_{*}$ and model-derived stellar parameters for the sample stars. The PAGB mass loss rates derived from the SED models are found to be higher than those for the AGB stars. In a few objects, low and high excitation fine structure emission lines were identified, indicating their advanced stage of evolution. Further, IR vibration modes of fullerene (C$_{60}$) were detected for the first time in the PAGB star IRAS 21546+4721.