Circumbinary discs are commonly observed around post-asymptotic giant branch (AGB) systems and are known to play an important role in their evolution. Several studies have pointed out that a circumbinary disc interacts through resonances with the central binary and leads to angular momentum transfer from the central binary orbit to the disc. This interaction may be responsible for a substantial increase in the binary eccentricity. We investigate whether this disc eccentricity-pumping mechanism can be responsible for the high eccentricities commonly found in post-AGB binary systems.
An interferometric study of the post-AGB binary 89 Herculis. II Radiative transfer models of the circumbinary disk
后AGB双星中普遍存在盘和外流。在本系列的第一篇论文中，我们发现在89 Her post-AGB系统中，有很大一部分可见光被分辨出来。数据显示，这种流量来自靠近中心的双星。有两种可能的来源是从环双星盘的内缘散射，或在尘埃外流中。详细的尘埃辐射转移模型的磁盘，我们的目标是区分这两种配置。通过包括Herschel/SPIRE测光，我们扩展了SED，使其现在完全覆盖紫外线到亚毫米波长。MCMax辐射转移代码用于创建一个大网格的磁盘模型。我们的模型包括一个自洽的处理灰尘沉降以及散射。测试了具有两个附加不透明度源（金属Fe或无定形C）的富Si组合物。SED与中红外（IR）光谱以及论文I中的光学和近红外光谱配合在一起，以约束盘的结构，特别是其内缘的结构。近红外可见度数据需要一个光滑的内缘，在这里得到的径向表面密度分布的两个幂律参数化。可以找到一个模型，适合所有的红外测光和干涉数据以及，与两个连续不透明度源。我们的最佳拟合被动模型的特点是大量的毫米大小的颗粒，这是解决了磁盘的中平面。没有一个单一的磁盘模型适合我们的数据在光学波长，虽然，原因是光学和近红外干涉数据所施加的相反的约束。一个被动的，充满尘埃的，膨胀的环双星盘存在的几何形状，可以复制所有的红外线，但不是89赫的光学观测。另一个尘埃，外流或晕，组件，因此需要添加到系统。
VLTI/PIONIER imaging of post-AGB binaries. An INSPIRING hunt for inner rim substructures in circumbinary discs
KU Leuven（荷鲁文大学）；Macquarie University（麦考瑞大学）；European Southern Observatory（欧洲南方天文台）；Observatorio Astronómico Nacional (OAN-IGN)（国家天文观测台（OAN-IGN））；Georgia State University（佐治亚州立大学）
本文利用VLTI/PIONIER干涉成像技术，研究后AGB双星系统的内 rim 结构，揭示可能的子结构，发现四个目标存在异常亮度增强，可能由辐射或动力学响应或流体不稳定性引起。
We focus on post-asymptotic giant branch (post-AGB) binaries and study the interaction between the different components of these complex systems. These components comprise the post-AGB primary, a main sequence secondary, a circumbinary disk, as well as a fast bipolar outflow (jet) launched by the companion. We obtained well-sampled time series of high resolution optical spectra over the last decade and these spectra provide the basis of our study. The jet is detected in absorption, at superior conjunction, when the line of sight towards the primary goes through the bipolar cone. Our spectral t…
Binary post-asymptotic giant branch (post-AGB) stars have orbital periods in the range of 100--2500 days in eccentric orbits. They are surrounded by circumbinary dusty discs. They are the immediate result of unconstrained binary interaction processes. Their observed orbital properties do not correspond to model predictions: Neither the periods nor the high eccentricities are expected. Our goal is to investigate if interactions between a binary and its circumbinary disc during the post-AGB phase can result in their eccentric orbits, while simultaneously explaining the chemical anomaly known as …
An interferometric study of the post-AGB binary 89 Herculis I Spatially resolving the continuum circumstellar environment at optical and near-IR wavelengths with the VLTI, NPOI, IOTA, PTI, and the CHARA Array
We present X-ray through submillimeter observations of the classical RV Tauri (RVb-type) variable U Mon, a post-AGB binary with a circumbinary disk (CBD). Our SMA observations indicate a CBD diameter of $\lesssim$550 au. Our XMM-Newton observations make U Mon the first RV Tauri variable detected in X-rays. The X-ray emission is characteristic of a hot plasma ($\sim$10 MK), with L$_{X}=5\times10^{30}{\rm erg}~{\rm s}^{-1}$, and we consider its possible origin from U Mon, its companion, and/or binary system interactions. Combining DASCH and AAVSO data, we extend the time-series photometric basel…
The presence of stable, compact circumbinary discs of gas and dust around post-asymptotic giant branch (post-AGB) binary systems has been well established. We focus on one such system: IRAS 08544-4431. We present an interferometric multi-wavelength analysis of the circumstellar environment of IRAS 08544-4431. The aim is to constrain different contributions to the total flux in the H, K, L, and N-bands in the radial direction. The data from VLTI/PIONIER, VLTI/GRAVITY, and VLTI/MATISSE range from the near-infrared, where the post-AGB star dominates, to the mid-infrared, where the disc dominates.…
Aims. In this study, we determine the morphology and mass-loss rate of jets emanating from the companion in post-asymptotic giant branch (post-AGB) binary stars with a circumbinary disk. In doing so, we also determine the mass accretion rates on to the companion and investigate the source feeding the circum-companion accretion disk. Methods. We perform a spatio-kinematic modelling of the jet of two well-sampled post-AGB binaries, BD+46442 and IRAS19135+3937, by fitting the orbital phased time series of H-alpha spectra. Once the jet geometry, velocity and scaled density structure are computed, …
ALMA's sharpest view of IRAS 08544-4431: Unveiling the dust distribution asymmetries in the circumbinary disk
Macquarie University（麦考瑞大学）；INAF, Osservatorio Astronomico di Roma（意大利国家天体物理研究所罗马天文台）；ATNF, CSIRO, Space and Astronomy（澳大利亚联邦科学与工业研究组织空间与天文部射电天文国家设施）；KU Leuven（荷语鲁汶大学）
The new generation of VLTI instruments (GRAVITY, MATISSE) aims to produce routinely interferometric images to uncover the morphological complexity of different objects at high angular resolution. Image reconstruction is, however, not a fully automated process. Here we focus on a specific science case, namely the complex circumbinary environments of a subset of evolved binaries, for which interferometric imaging provides the spatial resolution required to resolve the immediate circumbinary environment. Indeed, many binaries where the main star is in the post-asymptotic giant branch (post-AGB) p…
We present a long-term optical spectroscopic study of the post-AGB binary system 89 Herculis, with the aim to characterize the relationship between photospheric instabilities and dynamics in the close circumstellar environment of the system. This study is based on spectra acquired with the high-resolution Catania Astrophysical Observatory Spectropolarimeter and archive data, covering a time interval between 1978 and 2018. We find long-term changes in the radial velocity curve of the system, occurring mostly in amplitude, which correlate with the variability observed in the blue-shifted absorpt…
Infrared Variability from Circumbinary Disc Temperature Modulations
环双星盘边缘的温度应该会因照明的变化而波动，这是双星轨道相位的函数。我们探讨环双星盘温度变化作为宽带红外线曲线变异性的来源。将环双星盘边缘的壁近似为一个宽的光学厚圆柱体，表面温度依赖于其照度，我们发现，由1 M $_\odot$和0.5 M $_\odot$组成的双星在$\sim$ 15.5天的周期内，在3.77和4.68 μm处表现出最大的振幅变化$\sim$ 9%。光变曲线的变化幅度和形状对双星中恒星的光度和质量比、环双星盘的半径、双星分离和轨道倾角都很敏感。光变曲线的变化是平滑的，非常红，对于探索的大部分参数空间具有非正弦形状。可能的形态包括具有平坦区域的单个峰、不同高度的两个峰或单个凹陷。
B[e] supergiants have unusual circumstellar environments which may include thin, concentric rings displaying atomic line emission. GG Carinae is a B[e] supergiant binary which exhibits such a geometry in its circumbinary environment. We study atomic emission lines arising from GG Carinae's circumbinary disc in FEROS spectra collected between 1998 and 2015. We find that semi-forbidden Fe\,II] and permitted Ca\,II emission are formed in the same thin circumbinary ring previously reported to have forbidden [O\,I] and [Ca\,II] emission. We find that there are two circumbinary rings orbiting with p…
On The Secular Evolution of GG Tau A Circumbinary Disc: A Msialigned Disc Scenario
据观测，双星系统GG Tau A有一个环双星盘，其尘埃环比预期的更远，假设它是一个共面盘，相应的半长轴为34 AU。考虑到双星的分离，这个大的空洞可以通过放松共面圆盘的假设来解释，而是用一个偏心双星周围的未对准的环双星圆盘来拟合观测结果，该偏心双星的半长轴较宽，为60 AU，与系统的自行数据拟合一致。我们运行SPH模拟来检查这种可能性，我们确实发现，30度的失准角和0.45的二进制偏心符合天体测量数据和盘腔。然而，这样的配置原则上可能对极性不稳定，而不是对平面对准不稳定。我们调查这种配置的长期演变，并表明它确实是稳定的整个光盘的寿命。
Jets are a commonly observed phenomenon in post-asymptotic giant branch (post-AGB) binaries. Due to the orbital motion of the binary, the jet causes variable absorption in the Balmer profiles. In previous work, we have developed spatio-kinematic and radiative transfer models to reproduce the observed Balmer line variability and derive the spatio-kinematic structure of the jet and its mass-loss rate. Here, we apply our jet model to five post-AGB binaries with distinct Hα line variability and diverse orbital properties. Our models fit the Hα line variations very well. We estimate jet mass-loss r…
