Enstatite-rich Warm Debris Dust around HD165014

TL;DR

This study reports the discovery of an enstatite-rich warm debris disk around HD165014, highlighting unique crystalline silicate composition and implications for dust processing and planetary body formation.

Contribution

First detection of an enstatite-dominated crystalline silicate debris disk around a main-sequence star, expanding understanding of dust composition in warm debris disks.

Findings

Enstatite is the dominant crystalline silicate in the disk.

The dust temperature ranges from 300-750 K, at 0.7-4.4 AU from the star.

The disk shows large excess emission at wavelengths >5 μm.

Abstract

We present the Spitzer/Infrared Spectrograph spectrum of the main-sequence star HD165014, which is a warm (>~ 200 K) debris disk candidate discovered by the AKARI All-Sky Survey. The star possesses extremely large excess emission at wavelengths longer than 5 \mum. The detected flux densities at 10 and 20 \mum are ~ 10 and ~ 30 times larger than the predicted photospheric emission, respectively. The excess emission is attributable to the presence of circumstellar warm dust. The dust temperature is estimated as 300-750 K, corresponding to the distance of 0.7-4.4 AU from the central star. Significant fine-structured features are seen in the spectrum and the peak positions are in good agreement with those of crystalline enstatite. Features of crystalline forsterite are not significantly seen. HD165014 is the first debris disk sample that has enstatite as a dominant form of crystalline silicate rather than forsterite. Possible formation of enstatite dust from differentiated parent bodies is suggested according to the solar system analog. The detection of an enstatite-rich debris disk in the current study suggests the presence of large bodies and a variety of silicate dust processing in warm debris disks.