An edge-on translucent dust disk around the nearest AGB star, L2 Puppis - VLT/NACO spectro-imaging from 1.04 to 4.05 μm and VLTI interferometry
An edge-on translucent dust disk around the nearest AGB star, L2 Puppis - VLT/NACO spectro-imaging from 1.04 to 4.05 μm and VLTI interferometry
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最近的 AGB 恒星 L2 Puppis 周围的边缘半透明尘埃盘 - VLT/NACO 光谱成像（1.04 至 4.05 μm）和 VLTI 干涉测量
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发表时间：
2014
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通讯作者：
A. Gallenne
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作者：
P. Kervella;M. Montargès;S. Ridgway;G. Perrin;O. Chesneau;S. Lacour;A. Chiavassa;X. Haubois;A. Gallenne
作为离我们最近的已知AGB恒星（d=64pc）和最亮的恒星之一（mK~ 2）， L2 Pup是监测恒星演化最后阶段的一个特别有趣的基准对象。我们报告了VLT/NACO自适应光学系统在12个覆盖1.0-4.0微米波长范围的窄带滤光片上对这颗恒星的新的幸运成像观测。这些衍射极限图像揭示了恒星前方延伸的星周尘埃带，在J波段表现出高度的不透明度，在H和K波段变得半透明。在L波段，探测到来自尘埃的扩展热发射。我们使用RADMC-3D代码对尘埃盘进行蒙特卡罗辐射传输建模，再现了这些观测结果。我们也提出了新的干涉观测与VLTI/VINCI和MIDI仪器。我们在K波段测量了ta_ld的边缘暗角直径的上限= 17.9 +/- 1.6 mas，转换为R = 123 +/- 14 Rsun的最大线性半径。考虑到NACO图像中扩展的K波段发射的几何形状，这个上限可能接近恒星的实际角直径。L2 Pup在赫斯普龙-罗素图中的位置表明，这颗恒星的质量约为2 Msun，可能正在经历渐近巨星分支的早期阶段。在我们的自适应光学和干涉观测中，我们没有发现L2 Pup的任何伴星，我们将其在Hipparcos数据中明显的天体测量抖动归因于其星周物质的可变照明效应。然而，我们并不排除双星伴星的存在，因为在我们的L波段图像中，向圆盘东北方向延伸超过10 AU的大环结构可能是L2 Pup的恒星风与隐藏的次级天体相互作用的结果。我们提出的几何结构，有一个大的尘埃盘几乎是侧面的，似乎特别有利于测试和发展我们对双极星云形成的理解。
As the nearest known AGB star (d=64pc) and one of the brightest (mK~-2), L2 Pup is a particularly interesting benchmark object to monitor the final stages of stellar evolution. We report new lucky imaging observations of this star with the VLT/NACO adaptive optics system in twelve narrow band filters covering the 1.0-4.0 microns wavelength range. These diffraction limited images reveal an extended circumstellar dust lane in front of the star, that exhibits a high opacity in the J band and becomes translucent in the H and K bands. In the L band, extended thermal emission from the dust is detected. We reproduce these observations using Monte-Carlo radiative transfer modeling of a dust disk with the RADMC-3D code. We also present new interferometric observations with the VLTI/VINCI and MIDI instruments. We measure in the K band an upper limit to the limb-darkened angular diameter of theta_LD = 17.9 +/- 1.6 mas, converting to a maximum linear radius of R = 123 +/- 14 Rsun. Considering the geometry of the extended K band emission in the NACO images, this upper limit is probably close to the actual angular diameter of the star. The position of L2 Pup in the Herzsprung-Russell diagram indicates that this star has a mass around 2 Msun and is probably experiencing an early stage of the asymptotic giant branch. We do not detect any stellar companion of L2 Pup in our adaptive optics and interferometric observations, and we attribute its apparent astrometric wobble in the Hipparcos data to variable lighting effects on its circumstellar material. We however do not exclude the presence of a binary companion, as the large loop structure extending to more than 10 AU to the North-East of the disk in our L band images may be the result of interaction between the stellar wind of L2 Pup and a hidden secondary object. The geometric configuration that we propose, with a large dust disk seen almost edge-on, appears particularly favorable to test and develop our understanding of the formation of bipolar nebulae.