Optical and infrared spectroscopic analysis of the post-AGB star candidate IRAS 19386+0155

Abstract

This work reports high-resolution spectroscopic stellar parameters and abundance analysis of the post-AGB star IRAS 19386+0155. The analysis of the high resolution spectrum shows that it has an effective temperature of T_eff=6800±100 K and a surface gravity of log g = 1.4±0.2. The abundance analysis reveals IRAS 19386+0155 to be a metal-poor object having [Fe/H]=-1.1. Carbon, oxygen and nitrogen are found to be slight underabundant than solar, and so are the α-elements (Mg, Si and Ca). The analysis of ISO spectra revealed an oxygen-rich envelope and showed crystalline silicate features. The dust envelope of this object was modelled using a Monte Carlo type numerical method and amorphous and crystalline silicate grains were considered. The photospheric temperature obtained through the optical spectroscopy was used to constrain these models. The Spectral Energy Distribuition (SED) of this object is broad and extensive suggesting the presence of a dust disk around IRAS 19386+0155.

Based on observations made with the 1.52 m telescope at the European Southern Observatory (La Silla, Chile) under the agreement with the CNPq-Observatório Nacional (Brazil) Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the UK) and with the participation of ISAS and NASA.