1,2Shu Wang, 1,3Zhuochao Huang, 1,2,4Xiaodian Chen, 4,5,1Junming He, 1,2Haomiao Huang
The Astrophysical Journal, 1009, 58
Open Access Link to Article [DOI: 10.3847/1538-4357/ae909c]
1CAS Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, People’s Republic of China
2School of Astronomy and Space Science, University of the Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
3School of Space and Earth Sciences, Beihang University, Beijing 102206, People’s Republic of China
4Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, People’s Republic of China
5School of Physics and Astronomy, Beijing Normal University, Beijing 100875, People’s Republic of China
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 μm, the stellar-subtracted mid-infrared excess declined by 14.0% ± 1.2%, 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 μm 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 multiepoch ratios gives tc = 87+17−12 yr, for which the Spitzer-normalized dust-excess ratio reaches 0.5 after one tc. HD 15407A is consistent with an evolved postimpact 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.
