用毫米波干涉法分辨Epsilon Eridani系统
The Epsilon Eridani System Resolved by Millimeter Interferometry
摘要：
我们从亚毫米阵列（SMA）在1.3毫米和从澳大利亚望远镜紧凑阵列（ATCA）在7毫米，达到角分辨率~4”（13 AU）的波江座的观测。波江座是距离太阳最近的碎片盘所在地，这些第一次毫米干涉仪观测揭示了两个不同的发射成分：（1）众所周知的外部尘埃带，虽然不规则，但在径向方向上清晰可见，（2）一个与恒星位置一致的未解析源。我们使用直接的模型拟合的毫米vibrium约束这两个组件的基本属性。拟合SMA数据的外带的简单高斯形状导致$64.4^{+2.4}_{-3.0}$ AU的径向位置和$20.2^{+6.0}_{-8.2}$ AU的FWHM（分数宽度$ΔR/R = 0.3$。采用带的幂律径向发射轮廓获得了类似的结果，尽管幂律指数不能有效地约束。在获得的噪声（0.2毫焦/梁），这些数据是一致的轴对称带模型，并没有显着的方位角结构，可能会引入系统中看不见的行星。这些数据也限制了行星带在$<9$ AU内的任何星心偏移，这不利于在高偏心率（$>0.1$）和宽（10个AU）轨道上的巨行星的存在。在这些长波长下，未分辨的中心分量的通量密度超过了恒星光球层的预测，在1.3毫米处的通量密度略显着，但在7毫米处的通量密度是几倍（对于光学恒星半径的光源大小，亮度温度为$13000 \pm 1600$ K）。我们把这种多余的辐射归因于来自恒星日冕或色球层的电离等离子体。
英文摘要：
We present observations of Epsilon Eridani from the Submillimeter Array (SMA) at 1.3 millimeters and from the Australia Telescope Compact Array (ATCA) at 7 millimeters that reach an angular resolution of ~4" (13 AU). These first millimeter interferometer observations of Epsilon Eridani, which hosts the closest debris disk to the Sun, reveal two distinct emission components: (1) the well-known outer dust belt, which, although patchy, is clearly resolved in the radial direction, and (2) an unresolved source coincident with the position of the star. We use direct model-fitting of the millimeter visibilities to constrain the basic properties of these two components. A simple Gaussian shape for the outer belt fit to the SMA data results in a radial location of $64.4^{+2.4}_{-3.0}$ AU and FWHM of $20.2^{+6.0}_{-8.2}$ AU (fractional width $ΔR/R = 0.3$. Similar results are obtained taking a power law radial emission profile for the belt, though the power law index cannot be usefully constrained. Within the noise obtained (0.2 mJy/beam), these data are consistent with an axisymmetric belt model and show no significant azimuthal structure that might be introduced by unseen planets in the system. These data also limit any stellocentric offset of the belt to $<9$ AU, which disfavors the presence of giant planets on highly eccentric ($>0.1$) and wide (10's of AU) orbits. The flux density of the unresolved central component exceeds predictions for the stellar photosphere at these long wavelengths, by a marginally significant amount at 1.3 millimeters but by a factor of a few at 7 millimeters (with brightness temperature $13000 \pm 1600$ K for a source size of the optical stellar radius). We attribute this excess emission to ionized plasma from a stellar corona or chromosphere.
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