标题： HD142527：使用SPHERE的定量圆盘偏振测量 显示英文标题

标题： HD142527: Quantitative disk polarimetry with SPHERE

摘要： 我们展示了围绕HD142527的原行星盘的高精度光度测定和偏振测定，重点是确定尘埃的散射参数。我们重新减少了来自SPHERE/VLT的ZIMPOL和IRDIS子仪器在VBB（735 nm）和H波段（1625 nm）的偏振差分成像数据。基于参考星差分成像的偏振和光度测量使我们能够精确地测量由恒星周围盘面散射的光的线性偏振强度和总强度。我们使用盘面多次散射的简单蒙特卡洛模拟来推导尘埃的三个散射参数的限制：最大偏振度$P_{\rm max}$、不对称参数$g$和单次散射反照率$\omega$。我们分别在VBB和H波段测量到反射总强度为$51.4\pm1.5$mJy和$206\pm12$mJy，以及偏振强度为$11.3\pm0.3$mJy和$55.1\pm3.3$mJy。 我们还在可见光范围内发现了一个偏振度，在盘的远侧为 $28\%$，而在近侧为 $17\%$。 盘面显示散射光强度和偏振强度呈现出红色，当与可见光相比时，在近红外波段大约高出两倍。 通过模型计算确定了尘埃颗粒的散射特性，并发现在盘面远侧的两个观测波长处存在强烈的前向散射（$g\approx 0.5-0.75$）、相对较低的单次散射反照率（$\omega \approx 0.2-0.5$）以及高最大偏振（$P_{\rm max} \approx 0.5-0.75$）。 光学参数表明存在大团聚态尘埃颗粒，这些颗粒对于解释高最大偏振、尘埃强烈的前向散射性质以及观测到的盘面红色至关重要。 显示英文摘要

摘要： We present high-precision photometry and polarimetry for the protoplanetary disk around HD142527, with a focus on determining the light scattering parameters of the dust. We re-reduced polarimetric differential imaging data of HD142527 in the VBB (735 nm) and H-band (1625 nm) from the ZIMPOL and IRDIS subinstruments of SPHERE/VLT. With polarimetry and photometry based on reference star differential imaging, we were able to measure the linearly polarized intensity and the total intensity of the light scattered by the circumstellar disk with high precision. We used simple Monte Carlo simulations of multiple light scattering by the disk surface to derive constraints for three scattering parameters of the dust: the maximum polarization of $P_{\rm max}$, the asymmetry parameter $g$, and the single-scattering albedo $\omega$. We measure a reflected total intensity of $51.4\pm1.5$ mJy and $206\pm12$ mJy and a polarized intensity of $11.3\pm0.3$ mJy and $55.1\pm3.3$ mJy in the VBB and H-band, respectively. We also find in the visual range a degree of polarization that varies between $28\%$ on the far side of the disk and $17\%$ on the near side. The disk shows a red color for the scattered light intensity and the polarized intensity, which are about twice as high in the near-infrared when compared to the visual. We determine with model calculations the scattering properties of the dust particles and find evidence for strong forward scattering ($g\approx 0.5-0.75$), relatively low single-scattering albedo ($\omega \approx 0.2-0.5$), and high maximum polarization ($P_{\rm max} \approx 0.5-0.75$) at the surface on the far side of the disk for both observed wavelengths. The optical parameters indicate the presence of large aggregate dust particles, which are necessary to explain the high maximum polarization, the strong forward-scattering nature of the dust, and the observed red disk color.