INNER EDGES OF COMPACT DEBRIS DISKS AROUND METAL-RICH WHITE DWARFS
INNER EDGES OF COMPACT DEBRIS DISKS AROUND METAL-RICH WHITE DWARFS
复制标题
DOI：
10.1088/0004-637x/760/2/123
复制
发表时间：
2012-07
期刊：
影响因子：
--
通讯作者：
R. Rafikov;José A. Garmilla
中科院分区：
文献类型：
--
作者：
R. Rafikov;José A. Garmilla
一些富含金属的白色矮星（WD）被认为拥有致密的粒子盘，这被认为是这些恒星金属污染的原因。在许多这样的系统中，从它们的光谱推断出的盘的内半径是如此接近WD，以至于直接暴露于星光的粒子必须被加热到1500 K以上，并且预计对升华是不稳定的。为了调和这一期望与观测，我们探讨粒子升华的H-穷人碎片磁盘周围的WD。我们表明，由于高的金属蒸汽压，在这些磁盘的特征升华温度是300-400 K高于其原行星类似物，使粒子在更高的温度下生存。然后，我们看看碎片盘的内部边缘的结构，并表明它们应该具有过热的内部边缘，直接暴露于星光，温度达到2500-3500 K。粒子通过边缘向WD迁移（并迅速升华），使其后面的盘免受强烈的恒星加热，使固体的生存可能接近WD。只要盘颗粒由橄榄石等富含硅的材料组成，并且尺寸在0.03-30厘米范围内，我们的模型与WD+盘系统的观察结果非常一致。
A number of metal-rich white dwarfs (WDs) are known to host compact, dense particle disks, which are thought to be responsible for metal pollution of these stars. In many such systems, the inner radii of disks inferred from their spectra are so close to the WD that particles directly exposed to starlight must be heated above 1500 K and are expected to be unstable against sublimation. To reconcile this expectation with observations, we explore particle sublimation in H-poor debris disks around WDs. We show that because of the high metal vapor pressure the characteristic sublimation temperature in these disks is 300–400 K higher than in their protoplanetary analogs, allowing particles to survive at higher temperatures. We then look at the structure of the inner edges of debris disks and show that they should generically feature superheated inner rims directly exposed to starlight with temperatures reaching 2500–3500 K. Particles migrating through the rim toward the WD (and rapidly sublimating) shield the disk behind them from strong stellar heating, making the survival of solids possible close to the WD. Our model agrees well with observations of WD+disk systems provided that disk particles are composed of Si-rich material such as olivine, and have sizes in the range ∼0.03–30 cm.