发表机构
University of Warwick; Kobe University（华威大学; 神户大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究明确了年轻炽热白矮星周围不同类型小行星的固态物质存活临界距离，证实升华速度快于轨道漂移，并为白矮星污染的动力学起源场景提供了支持。
AI 中文摘要
所有观测到的围绕单颗白矮星运行的行星系统，都经历了恒星从渐近巨星分支（AGB）阶段的炽热转变。在这个星云后转变时期，白矮星冷却过程中行星系统演化的初始条件得以确立。最炽热（温度≥20000K）、最年轻（年龄≤20Myr）的白矮星行星系统宿主恒星，与典型的更古老、温度更低的同类天体存在显著差异——它们无法在白矮星紧邻区域（几个太阳半径范围内）维持固态物质的聚集。本研究分析了这一关键时期固态物质存活的可能位置、升华产生的气态物质含量及其相关后果。研究发现：（i）后续会显著污染白矮星的富铁、岩石质和富水小行星（半径为R）的储库，在白矮星冷却的最初数千万年里，必须停留在临界距离之外，临界距离分别为：铁质小行星对应16天文单位×(1km/R)^(1/2)，岩石质小行星对应30天文单位×(1km/R)^(1/2)，冰雪质小行星对应130天文单位×(1km/R)^(1/2)；（ii）升华过程的发生速度远快于由坡印廷-罗伯逊 drag（阻力）或雅科夫斯基效应驱动的轨道漂移速度；（iii）尽管被踢入新生白矮星高偏心率轨道的大型小行星（半径R≈10-1000km）能够在升华中存活，但它们可能碎裂成碎片，这些碎片会在白矮星冷却前发生升华。这些结果支持但不强制要求，白矮星污染的动力学起源场景——即宿主恒星的渐近巨星分支阶段之后，在柯伊伯带类距离及更远区域发生延迟引力不稳定性——成立。
英文摘要
All observed planetary systems orbiting single white dwarfs have lived through the hot stellar transition from an asymptotic giant branch star. In this post-nebular transition period, the initial conditions for planetary system evolution throughout white dwarf cooling are established. The hottest ($\gtrsim$ 20,000 K) and youngest ($\lesssim$ 20 Myr-old) white dwarf planetary system host stars differ significantly from their canonical older and colder counterparts by failing to support solid body accumulation in the immediate vicinity (a few $R_{\odot}$) of the white dwarf. Here, we analyse the likely locations of both solid-body survival and the sublimated gaseous content during this pivotal epoch, and the consequences. We find that (i) reservoirs of iron-rich, rocky and water-rich asteroids of radius $R$ that later observably enrich, or pollute, the white dwarf need to remain parked for the first tens of Myr of white dwarf cooling beyond critical distances of (16 au)$\times(1 {\rm km}/R)^{1/2}$ (for iron), (30 au)$\times(1 {\rm km}/R)^{1/2}$ (for rock) and (130 au)$\times(1 {\rm km}/R)^{1/2}$ (for snow), (ii) sublimation acts much more quickly than radiatively-driven orbital drifts from Poynting-Robertson drag or the Yarkovsky effect, and (iii) although large asteroids ($R \approx$ 10-1000 km) that are kicked on highly eccentric orbits around newly born white dwarfs could survive sublimation, they may fragment into debris which will sublime before the white dwarf cools. These results support, but do not necessitate, dynamical origin scenarios of polluted white dwarfs that feature delayed gravitational instability subsequent to the host star's asymptotic giant branch phase at Kuiper Belt-like distances, and beyond.
CommentsAccepted for publication in MNRAS
