BD +31643的极化冠状照相
Polarimetric coronagraphy of BD+31643
摘要：
上下文二元B5 V星BD+31？643显示出在光学波长处检测到的盘状结构。尽管这个特征很好地集中在恒星上，但根据斯皮策的观测，有人认为这个特征是一个与双星没有直接联系的灯丝。目标。本文的目的是调查是否偏振成像可以提供证据支持或反对磁盘假说。此外，我们的目标是澄清是否可能有任何额外的近伴星的双星。方法.我们在偏振模式下使用了电晕放电PolCor，并结合了EMCCD相机，允许短的单位曝光时间。作为移位相加和帧选择的结果，与传统CCD成像相比，空间分辨率得到提高。为了可能揭示一个额外的恒星伴侣，我们使用高分辨率光谱学在光学和高空间分辨率成像在近红外。盘/暗条在偏振中看得更清楚;它很窄，沿着脊画的一条线在距离恒星一弧秒的范围内通过。偏振度高（？在修正了反射星云的延伸部分后，这意味着盘/暗条必须与恒星的距离大致相同。虽然我们确认该特征在恒星东南方向比西北方向亮得多，但这一特征与恒星有物理联系的证据得到了加强，并表明我们正在目睹一个吸积盘的破坏过程。我们的光谱显示至少有一颗恒星是光谱双星。然而，除了两颗分离良好的恒星外，我们无法在空间上分辨任何恒星成分。
英文摘要：
Context. The binary B5V star BD+31?643 exhibits a disk-like structure detected at optical wavelengths. Even though the feature is well centered on the star, it has been argued, based on Spitzer observations, that the feature is a filament not directly associated to the binary star. Aims. The purpose of the present paper is to investigate whether polarization imaging may provide evidence either for or against the disk hypothesis. In addition, we aim at clarifying whether there might be any additional close companion to the binary star. Methods. We used the coronagraph PolCor in its polarization mode in combination with an EMCCD camera allowing short unit exposure times. As a result of shift-and-add and frame selection, the spatial resolution is improved compared to traditional CCD imaging. In order to possibly reveal an additional stellar companion, we used high resolution spectroscopy in the optical and high spatial resolution imaging in the near-IR. Results. The disk/filament is much better seen in polarization; it is narrow and a line drawn along the ridge passes within a second of arc from the star. The degree of polarization is high (?50% after correction for the extended component of the reflection nebula) which means that the disk/filament must be approximately at the same distance as the star. Although we confirm that the feature is much brighter south-east than north-west of the star, the evidence that the feature is physically connected to the star is strengthened and suggests that we are witnessing the destruction process of an accretion disk. Our spectroscopy shows that at least one of the stars is a spectroscopic binary. We were, however, not able to spatially resolve any stellar component in addition to the two well separated stars.
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