Dust production and depletion in evolved planetary systems
Dust production and depletion in evolved planetary systems
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DOI：
10.1093/mnras/sty2331
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发表时间：
2018-12-01
影响因子：
4.8
通讯作者：
Reach, W. T.
中科院分区：
文献类型：
--
作者：
Farihi, J.;van Lieshout, R.;Reach, W. T.
研究发现，白矮星 GD 56 的红外尘埃排放量在 11.2 年内峰峰值上升和下降了 20%，这与持续的尘埃产生和消耗是一致的。据推测，灰尘是通过与不断演变的尘埃盘相关的碰撞产生的，暂时增加了温暖碎片的发射表面，并随后在几年内被破坏或同化。这些变化与不改变温度的碎片一致，表明灰尘在固定的轨道半径范围内产生和消耗。碰撞中产生的气体可能会迅速重新凝结到颗粒上，或者可能会在粘性时间尺度上吸积到白矮星表面，该粘性时间尺度比微米级尘埃的坡印廷-罗伯逊阻力要长得多。尽管采样稀疏，但质量吸积率变化的这种潜在延迟与 GD 56 15 年来不变的 Ca If 和 Mg II 吸收特征的多历元光谱一致。总的来说，这些结果表明，无论是推断的还是观察到的，碰撞很可能是围绕大多数或所有被污染的白矮星运行的尘埃和气体的来源。
The infrared dust emission from the white dwarf GD 56 is found to rise and fall by 20 per cent peak-to-peak over 11.2 yr, and is consistent with ongoing dust production and depletion. It is hypothesized that the dust is produced via collisions associated with an evolving dust disc, temporarily increasing the emitting surface of warm debris, and is subsequently destroyed or assimilated within a few years. The variations are consistent with debris that does not change temperature, indicating that dust is produced and depleted within a fixed range of orbital radii. Gas produced in collisions may rapidly re-condense onto grains, or may accrete onto the white dwarf surface on viscous timescales that are considerably longer than Poynting-Robertson drag for micron-sized dust. This potential delay in mass accretion rate change is consistent with multi-epoch spectra of the unchanging Ca If and Mg II absorption features in GD 56 over 15 yr, although the sampling is sparse. Overall, these results indicate that collisions are likely to be the source of dust and gas, either inferred or observed, orbiting most or all polluted white dwarfs.