Dust production from collisions in extrasolar planetary systems. The inner beta Pictoris disc
Dust production from collisions in extrasolar planetary systems. The inner beta Pictoris disc
复制标题
太阳系外行星系统碰撞产生的尘埃。
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
H. Beust
中科院分区：
文献类型：
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作者：
P. Thebault;J. Augereau;H. Beust
在太阳系外行星盘中观察到的尘埃粒子来自无法探测到的千米大小的天体，但如果没有适当地了解颗粒和行星体之间的理论联系，这些有价值的信息仍然没有引起人们的兴趣。我们在这篇文章中概述了我们开发的一种数值方法，以解决产生尘埃的碰撞级联的这个问题。该模型基于箱中质点方法。根据不同的处方，我们跟踪了颗粒在半径上的八个数量级的尺寸分布，并考虑了碎裂和陨石坑。特别关注的是最小的粒子，接近辐射压力引起的截断大小的RPR，它们被恒星辐射压力置于高度偏心的轨道上。我们将我们的模型应用于内部(<；10AU)Pictoris盘的情况，以便定量地推导出在该区域观察到的少量尘埃(‘10 22g)所需的前驱粒子的数量。我们的模拟表明，从千米大小的天体到颗粒的碰撞级联显著偏离经典的dN/R3：5DR幂定律：最小的粒子(R’Rpr)被强烈地耗尽，而大小为2Rpr的过量颗粒和大小为100Rpr的一滴颗粒的发展与盘的动力学激发、RPR和初始表面密度无关。然而，全球尘埃与行星小质量之比仍接近其dN/R3：5DR值。因此，我们的严格方法证实了最初从有问题的假设中推断出的内侧毕托利圆盘的质量损耗。此外，我们还证明了碰撞是内部Pictoris盘中尘埃的重要来源。即使考虑到另一种情况，即通过缓慢蒸发千米大小的天体产生尘埃，它们实际上也是不可避免的。对于小于10AU的总质量，我们得到了0.1M的上限。这一上限与下落蒸发体(FEB)场景框架中的独立质量估计(至少15M)不一致，该场景解释了观测到的瞬变特征活动。此外，我们还表明，维持FEB活动所需的质量意味着一个如此重要的质量损失，以至于这种现象应该自然地在小于1Myr的时间内结束，即不到恒星年龄的二十分之一(至少2107年)。总而言之，这些结果可能有助于汇聚一幅内部皮托里斯系统的连贯图景：一个由可能形成行星胚胎后留下的低质量碰撞碎片组成的圆盘，这一结果将与该系统的估计年龄相一致。
Dust particles observed in extrasolar planetary discs originate from undetectable km-sized bodies but this valuable information remains uninteresting if the theoretical link between grains and planetesimals is not properly known. We outline in this paper a numerical approach we developed in order to address this issue for the case of dust producing collisional cascades. The model is based on a particle-in-a-box method. We follow the size distribution of particles over eight orders of magnitude in radius taking into account fragmentation and cratering according to dierent prescriptions. Particular attention is paid to the smallest particles, close to the radiation pressure induced cut-o size Rpr, which are placed on highly eccentric orbits by the stellar radiation pressure. We applied our model to the case of the inner (<10 AU) Pictoris disc, in order to quantitatively derive the population of progenitors needed to produce the small amount of dust observed in this region ('10 22 g). Our simulations show that the collisional cascade from kilometre-sized bodies to grains significantly departs from the classical d N/ R 3:5 dR power law: the smallest particles (R' Rpr) are strongly depleted while an overabundance of grains with size2Rpr and a drop of grains with size100Rpr develop regardless of the disc's dynamical excitation, Rpr and initial surface density. However, the global dust to planetesimal mass ratio remains close to its d N / R 3:5 dR value. Our rigorous approach thus confirms the depletion in mass in the inner Pictoris disc initially inferred from questionable assumptions. We show moreover that collisions are as ucient source of dust in the inner Pictoris disc. They are actually unavoidable even when considering the alternative scenario of dust production by slow evaporation of km-sized bodies. We obtain an upper limit of0.1 M for the total disc mass below 10 AU. This upper limit is not consistent with the independent mass estimate (at least 15 M) in the frame of the Falling Evaporating Bodies (FEB) scenario explaining the observed transient features activity. Furthermore, we show that the mass required to sustain the FEB activity implies a so important mass loss that the phenomena should naturally end in less than 1 Myr, namely in less than one twentieth the age of the star (at least 2 10 7 years). In conclusion, these results might help converge towards a coherent picture of the inner Pictoris system: a low-mass disc of collisional debris leftover after the possible formation of planetary embryos, a result which would be coherent with the estimated age of the system.
影响因子：
3.2
作者：
V. Mannings;A. Boss;S. Russell
通讯作者：
V. Mannings;A. Boss;S. Russell