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arXiv · 2607.21948

A Stable Mineral Fingerprint in the Fading Warm Debris Disk around HD 15407A

Shu Wang·Zhuochao Huang·Xiaodian Chen·Junming He·Haomiao Huang
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Abstract

Extreme debris disks provide time-domain probes of rocky planet assembly after giant impacts. We compare Spitzer and JWST spectra of the warm debris disk around HD 15407A, obtained 14.95 yr apart. Across 6-25$\mu$m, the stellar-subtracted mid-infrared excess declined by $14.0\pm1.2$%, while the mineral fingerprint is nearly unchanged. Within the adopted common reduced mineral basis, Mg-rich pyroxene dominates the normalized fitted mineral weights at about 65%, while silica and forsterite contribute about 22-23% and 12-13%, respectively. In both epochs, about 93-94% of the fitted mineral weight is carried by 5.0$\mu$m grains. The fitted optically thin surface-component amplitude drops by 32%, consistent with reduced mineral-emitting flux from the disk surface rather than the appearance of a new dust composition. A simple collisional-cascade guide fitted to the IRAS-to-JWST multi-epoch ratios gives $t_c=87^{+17}_{-12}$ yr, for which the Spitzer-normalized dust-excess ratio reaches 0.5 after one $t_c$. HD 15407A is consistent with an evolved post-impact reservoir with limited recent supply of very small grains: its rocky mineral fingerprint has remained stable since at least 2008, while its warm mineral-emitting flux is gradually fading over several hundred years.

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Shu Wang, Zhuochao Huang, Xiaodian Chen, Junming He, Haomiao Huang. 2026-07-24. A Stable Mineral Fingerprint in the Fading Warm Debris Disk around HD 15407A. https://arxiv.org/abs/2607.21948

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