Spitzer observations of V4332 Sagittarii: Detection of Alumina Dust

TL;DR

This study reports the detection of alumina dust in V4332 Sagittarii using Spitzer infrared observations, revealing a broad 10 micron feature that indicates alumina presence alongside silicates, and discusses implications for dust formation processes.

Contribution

First detection of alumina dust in V4332 Sagittarii, combining spectral analysis and radiative transfer modeling to identify alumina's role in dust composition.

Findings

Broad 10 micron absorption feature indicates alumina dust presence.

Radiative transfer modeling confirms alumina as necessary to explain the spectrum.

Detection of AlO radical supports alumina formation hypothesis.

Abstract

We present broad-band 24, 70 and 160 micron photometry, 5-35 micron and 55-90 micron spectra of the eruptive variable V4332 Sgr from Spitzer observations. The distinguishing feature of the 5-35 micron spectrum is an unusually broad absorption feature near 10 micron at the position generally associated with silicate-rich dust. Through radiative transfer modeling, we show that this broad feature cannot arise from silicates alone but requires the inclusion of alumina (Al2O3) as a dust condensate. The case for including Al2O3 is strengthened further by the presence of the AlO radical, a potentially important molecule in forming Al2O3. The present detection indicates that porous alumina manifests itself through a broadening of the 9.7 micron silicate feature and additionally displays, on the shoulder of the silicate feature, a component at ~11.5 micron. We discuss how further observations of V4332 Sgr may have the potential of verifying some general predictions of the dust condensation process.