The Absence of Cold Dust around Warm Debris Disk Star HD 15407A

TL;DR

This study uses Herschel and AKARI observations to analyze the debris disk around HD 15407A, revealing warm dust presence without accompanying cold dust, challenging previous theories about its origin.

Contribution

It provides the first FIR observations confirming the absence of cold dust in the debris disk, suggesting a different origin for the warm dust than late heavy bombardment.

Findings

FIR excess emission is consistent with warm dust only.

Cold dust (~50-130 K) is absent in the disk.

The warm dust likely has a different origin than late heavy bombardment.

Abstract

We report Herschel and AKARI photometric observations at far-infrared (FIR) wavelengths of the debris disk around the F3V star HD 15407A, in which the presence of an extremely large amount of warm dust (~500-600 K) has been suggested by mid-infrared (MIR) photometry and spectroscopy. The observed flux densities of the debris disk at 60-160 micron are clearly above the photospheric level of the star, suggesting excess emission at FIR as well as at MIR wavelengths previously reported. The observed FIR excess emission is consistent with the continuum level extrapolated from the MIR excess, suggesting that it originates in the inner warm debris dust and cold dust (~50-130 K) is absent in the outer region of the disk. The absence of cold dust does not support a late heavy bombardment-like event as an origin of the large amount of warm debris dust around HD 15047A.