论文标题
围绕AGB恒星HR3126的紧凑型灰尘盘的红外干涉成像与双极托比果冻星云
Infrared interferometric imaging of the compact dust disk around the AGB star HR3126 with the bipolar Toby Jug Nebula
论文作者
论文摘要
渐近巨型分支（AGB）恒星HR3126与高度尺度的双极Toby罐头星云有关，为研究AGB阶段结束时的双极结构的出现提供了难得的机会。 We carried out long-baseline interferometric observations with AMBER and GRAVITY (2--2.45 micron) at the Very Large Telescope Interferometer, speckle interferometric observations with VLT/NACO (2.24 micron), and imaging with SPHERE-ZIMPOL (0.55 micron) and VISIR (7.9--19.5 micron).从琥珀+重力数据中从2.1---2.29微米处重建的图像揭示了中央恒星，被椭圆形的环状结构包围，分别为5.3和3.5 mas，椭圆形环状结构分别为半隔轴和半轴轴。该环被解释为从〜50度倾斜角度观察的赤道灰尘盘的内边缘，其轴与双极星云大致对齐。磁盘令人惊讶地紧凑，内部半径仅为3.5 rstar（2 au）。我们的2-D辐射转移模型表明，具有硅酸盐晶粒的光学厚片磁盘（〜4微米）可以重现观察到的连续图像和光谱能量分布。在CO第一个泛音带中获得的图像显示了中央恒星周围的延长发射，表明恒星大气的含量或灰尘腔内的CO气盘存在。该物体未解决Sphere-Zimpol，Naco和Visir。如果磁盘与双极星云一起形成，则在〜3900年的动态时代，从亚微米到几微米的晶粒生长应发生。重建图像中伴侣的未检测意味着其2.2微米的亮度比红色巨人低约30倍，或者由于二进制相互作用而可能被切碎。
The asymptotic giant branch (AGB) star HR3126, associated with the arcminute-scale bipolar Toby Jug Nebula, provides a rare opportunity to study the emergence of bipolar structures at the end of the AGB phase. We carried out long-baseline interferometric observations with AMBER and GRAVITY (2--2.45 micron) at the Very Large Telescope Interferometer, speckle interferometric observations with VLT/NACO (2.24 micron), and imaging with SPHERE-ZIMPOL (0.55 micron) and VISIR (7.9--19.5 micron). The images reconstructed in the continuum at 2.1--2.29 micron from the AMBER+GRAVITY data reveal the central star surrounded by an elliptical ring-like structure with a semimajor and semiminor axis of 5.3 and 3.5 mas, respectively. The ring is interpreted as the inner rim of an equatorial dust disk viewed from an inclination angle of ~50 degrees, and its axis is approximately aligned with the bipolar nebula. The disk is surprisingly compact, with an inner radius of a mere 3.5 Rstar (2 au). Our 2-D radiative transfer modeling shows that an optically thick flared disk with silicate grains as large as ~4 micron can reproduce the observed continuum images and the spectral energy distribution. The images obtained in the CO first overtone bands reveal elongated extended emission around the central star, suggesting the oblateness of the star's atmosphere or the presence of a CO gas disk inside the dust cavity. The object is unresolved with SPHERE-ZIMPOL, NACO, and VISIR. If the disk formed together with the bipolar nebula, the grain growth from sub-micron to a few microns should have taken place over the nebula's dynamical age of ~3900 yrs. The non-detection of a companion in the reconstructed images implies that either its 2.2 micron brightness is more than ~30 times lower than that of the red giant or it might have been shredded due to binary interaction.
