The cold origin of the warm dust around ε Eridani
The cold origin of the warm dust around ε Eridani
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波江座 ε 周围温暖尘埃的冷起源
DOI：
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发表时间：
2010
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通讯作者：
S. Mueller
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文献类型：
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作者：
Martin Reidemeister;A. Krivov;C. Stark;J. Augereau;T. Loehne;S. Mueller
语境。附近的 K2 V 恒星 e Eridani 拥有一颗已知的内行星、一个外柯伊伯带类似物和一个由温暖尘埃组成的内盘。斯皮策/IRS 测量表明，温暖的尘埃存在于距离恒星近几个天文单位的地方。它的起源令人费解，因为由于已知的内行星，可能产生这种尘埃的“小行星带”会不稳定。目标。在这里，我们测试了一个假设，即观测到的温暖尘埃是由外带碰撞产生的，并通过坡印廷-罗伯逊阻力和强烈的恒星风向内输送。方法。我们使用碰撞代码模拟了 10 个天文单位外部尘埃粒子的稳态分布，并使用单粒子数值积分模拟了内部区域 (r < 10 个天文单位) 的尘埃粒子稳态分布。通过假设由冰和星状硅酸盐组成的均匀球形尘埃颗粒，我们计算了尘埃的热发射，并将其与观测结果进行了比较。我们研究了根据径向速度测量推断出的内行星的两种不同轨道配置，一种具有 e = 0.7 的高偏心率轨道，另一种具有 e = 0.25 的中等偏心率轨道。我们还制作了一个没有行星的模拟。结果。我们的模型可以重现从中红外到亚毫米波长观察到的光谱能量分布的形状和大小，以及 Spitzer/MIPS 径向亮度分布。最合适的粉尘成分包括水冰和硅酸盐。对于两个可能的行星轨道和没有行星的情况，结果是相似的。结论。在波江座系统中观测到的温暖尘埃确实可以源自外部“柯伊伯带”，并通过坡印廷-罗伯逊和恒星风拖曳向内输送。内行星对尘埃分布的影响很小，因此行星轨道不会受到限制。只有放宽纯硅酸盐尘埃的假设并假设硅酸盐和水冰的混合物数量相当，才能实现模型与观测结果之间的合理一致性。
Context. The nearby K2 V star e Eridani hosts one known inner planet, an outer Kuiper belt analog, and an inner disk of warm dust. Spitzer/IRS measurements indicate that the warm dust is present at distances as close as a few AU from the star. Its origin is puzzling, since an “asteroid belt” that could produce this dust would be unstable because of the known inner planet. Aims. Here we test a hypothesis that the observed warm dust is generated by collisions in the outer belt and is transported inward by Poynting-Robertson drag and strong stellar winds. Methods. We simulated a steady-state distribution of dust particles outside 10 AU with a collisional code and in the inner region (r < 10 AU) with single-particle numerical integrations. By assuming homogeneous spherical dust grains composed of ice and astrosilicate, we calculated the thermal emission of the dust and compared it with observations. We investigated two different orbital configurations for the inner planet inferred from radial velocity measurements, one with a highly eccentric orbit of e = 0.7 and another one with a moderate eccentricity of e = 0.25. We also produced a simulation without a planet. Results. Our models can reproduce the shape and magnitude of the observed spectral energy distribution from mid-infrared to submillimeter wavelengths, as well as the Spitzer/MIPS radial brightness profiles. The best-fit dust composition includes both water ice and silicates. The results are similar for the two possible planetary orbits and without a planet. Conclusions. The observed warm dust in the e Eridani system can indeed stem from the outer “Kuiper belt” and be transported inward by Poynting-Robertson and stellar wind drag. The inner planet has little effect on the distribution of dust, so that the planetary orbit could not be constrained. Reasonable agreement between the model and observations can only be achieved by relaxing the assumption of purely silicate dust and assuming a mixture of silicate and water ice in comparable amounts.