Optical properties of amorphous alumina dust in the envelopes around O-rich AGB stars

TL;DR

This study models the optical properties of amorphous alumina dust in O-rich AGB star envelopes, showing that mixed alumina-silicate dust better explains observed infrared spectra.

Contribution

It derives optical constants for amorphous alumina consistent with laboratory data and demonstrates improved spectral fits using mixed dust models.

Findings

Amorphous alumina constitutes 10-40% of dust in O-rich AGB envelopes.

Mixed alumina-silicate dust models better match observed IR spectra.

Laboratory-measured optical data effectively inform astrophysical dust modeling.

Abstract

We investigate optical properties of amorphous alumina (Al_2O_3) dust grains in the envelopes around O-rich asymptotic giant branch (AGB) stars considering the laboratory measured optical data. We derive the optical constants of amorphous alumina in a wide wavelength range that satisfy the Kramers-Kronig relation and reproduce the laboratory measured data. Using the amorphous alumina and silicate dust, we compare the radiative transfer model results with the observed spectral energy distributions. Comparing the theoretical models with the observations on various IR two-color diagrams for a large sample O-rich AGB stars, we find that the amorphous alumina dust (about 10-40 %) mixed with amorphous silicate can reproduce much more observed points for the O-rich AGB stars with thin dust envelopes.