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arXiv 1202.3784astro-ph.EPastro-ph.SR
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潮汐破坏岩石行星体对天体寿命的限制

Constraints on the Lifetimes of Disks Resulting from Tidally Destroyed Rocky Planetary Bodies

J. Girven, C. S. Brinkworth, J. Farihi, B. T. Gänsicke, D. W. Hoard, T. R. Marsh, D. Koester

备注：
20 pages, 9 figures, accepted to be published in ApJ
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摘要：

斯皮策IRAC对15颗金属污染的白矮星的观测揭示了HE 0110-5630、GD 61和HE 1349-2305光谱能量分布中的红外过量。这三颗恒星都有以氦为主的大气层，它们的红外辐射与（小）行星体潮汐破坏产生的温暖尘埃一致。这项研究使IRAC调查的金属污染，氦和氢大气白矮星的数量分别达到53和38。它也几乎是斯皮策发现的有近轨道尘埃的金属污染的富氦白矮星数量的两倍。从这两种具有星周尘埃的大气类型的统计数据中，我们得出了典型的圆盘寿命log[ t_{disk}（年）] = 5.6+-1.1（3*10^4 - 5*10^6年）。这是假设在尘埃存在的时间尺度上有一个相对恒定的吸积速率，这是不确定的。我们发现，由斯皮策探测到的具有红外过量的高度金属污染的富氦白矮星的比例仅为23%，而金属污染的富氢白矮星的比例为48%，并且我们从这种差异得出结论，尘埃盘的典型寿命比富氦白矮星的扩散时间尺度要短。我们还发现了证据，以更高的时间平均吸积率到富氦恒星的瞬时吸积率到富氢恒星相比，这是一个迹象，我们的图片演变的恒星-行星系相互作用是不完整的。我们讨论了一些推测性的情况下，可以解释的意见。

英文摘要：

Spitzer IRAC observations of 15 metal-polluted white dwarfs reveal infrared excesses in the spectral energy distributions of HE 0110-5630, GD 61, and HE 1349-2305. All three of these stars have helium-dominated atmospheres, and their infrared emissions are consistent with warm dust produced by the tidal destruction of (minor) planetary bodies. This study brings the number of metal-polluted, helium and hydrogen atmosphere white dwarfs surveyed with IRAC to 53 and 38 respectively. It also nearly doubles the number of metal-polluted helium-rich white dwarfs found to have closely orbiting dust by Spitzer. From the increased statistics for both atmospheric types with circumstellar dust, we derive a typical disk lifetime of log[t_{disk} (yr)] = 5.6+-1.1 (ranging from 3*10^4 - 5*10^6 yr). This assumes a relatively constant rate of accretion over the timescale where dust persists, which is uncertain. We find that the fraction of highly metal-polluted helium-rich white dwarfs that have an infrared excess detected by Spitzer is only 23 per cent, compared to 48 per cent for metal-polluted hydrogen-rich white dwarfs, and we conclude from this difference that the typical lifetime of dusty disks is somewhat shorter than the diffusion time scales of helium-rich white dwarf. We also find evidence for higher time-averaged accretion rates onto helium-rich stars compared to the instantaneous accretion rates onto hydrogen-rich stars; this is an indication that our picture of evolved star-planetary system interactions is incomplete. We discuss some speculative scenarios that can explain the observations.

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