A few years ago, the mid-IR spectrum of a Weak Line T Tauri Star, CoKu Tau/4, was explained as emission from the inner wall of a circumstellar disk, with the inner disk truncated at ~10 AU. Based on the SED shape and the assumption that it was produced by a single star and its disk, CoKu Tau/4 was classified as a prototypical transitional disk, with a clean inner hole possibly carved out by a planet, some other orbiting body, or by photodissociation. However, recently it has been discovered that CoKu Tau/4 is a close binary system. This implies that the observed mid-IR SED is probably produced by the circumbinary disk. The aim of the present paper is to model the SED of CoKu Tau/4 as arising from the inner wall of a circumbinary disk, with parameters constrained by what is known about the central stars and by a dynamical model for the interaction between these stars and their surrounding disk. In order to fit the Spitzer IRS SED, the binary orbit should be almost circular, implying a small mid-IR variability (10%) related to the variable distances of the stars to the inner wall of the circumbinary disk. Our models suggest that the inner wall of CoKu Tau/4 is located at 1.7a, where a is the semi-major axis of the binary system (a~8AU). A small amount of optically thin dust in the hole (<0.01 lunar masses) helps to improve the fit to the 10microns silicate band. Also, we find that water ice should be absent or have a very small abundance (a dust to gas mass ratio <5.6X10^{-5}). In general, for a binary system with eccentricity e>0, the model predicts mid-IR variability with periods similar to orbital timescales, assuming that thermal equilibrium is reached instantaneously.
Context. With its high complexity, large size, and close distance, the ringworld around GG Tau A is an appealing case to study the formation and evolution of protoplanetary disks around multiple star systems. However, investigations with radiative transfer models are usually neglecting the influence of the circumstellar dust around the individual stars. Aims. We investigate how circumstellar disks around the stars of GG Tau A are influencing the emission that is scattered at the circumbinary disk and if constraints on these circumstellar disks can be derived. Methods. We perform radiative tran…
We present high resolution millimeter continuum and CO line observations for the circumbinary disk around V892 Tau to constrain the stellar and disk properties. The total mass of the two near-equal-mass A stars is estimated to be $6.0\pm0.2\,M_{\odot}$ based on our models of the Keplerian-dominated gas disk rotation. The detection of strong ionized gas emission associated with the two stars at 8 mm, when combined with previous astrometric measurements in the near-infrared, provides an updated view of the binary orbit with $a=7.1\pm0.1$ au, $e=0.27\pm0.1$, and $P=7.7\pm0.2$ yr, which is about h…
A deep (~70%) and extended (~150 days) eclipse was seen towards the young multiple stellar system V773 Tau in 2010. We interpret it as due to the passage of a circumbinary disk around the B components moving in front of the A components. Our aim is to characterise the orientation and structure of the disk, to refine the orbits of the subcomponents, and to predict when the next eclipse will occur. We combine the photometry from several ground based surveys, construct a model for the light curve of the eclipse, and use high angular resolution imaging to refine the orbits of the three components …
Resolved Multifrequency Radio Observations of GG Tau
我们目前的亚弧秒分辨率观测的连续辐射与GG头四星系统在1.3，2.8，7.3，和50毫米的波长。这些数据证实，GG头A的二进制包围的circumbinary环在半径为235 AU的半高宽约60 AU。我们没有发现环的光谱形状中存在径向梯度的明确证据，这表明粒度分布在~0.1”的角尺度上是空间均匀的。一个中心点源，可能与主要成分（GG Tau Aa）有关，表现出尘埃和自由-自由发射的复合光谱。在低质量恒星GG Tau Ba附近观测到7.3毫米的微弱辐射，尽管其来源仍然不确定。使用这些测量的解决，多频发射结构的GG头A系统，模型的远红外线到无线电频谱的发展，把约束的粒度分布和尘埃质量的环双星环。环谱中存在的不可忽略的曲率意味着最大粒径为1-10 mm，尽管我们无法对分布形状施加强约束。相应的尘埃质量为30-300 M地球，温度为20-30 K。我们讨论了在大半径的窄环中相对大的颗粒的这种显著浓度如何可能在较高气体压力的局部区域中产生（即，一个粒子“陷阱”）位于环双星盘的内缘附近。
We analyzed the young (2.8-Myr-old) binary system FS Tau A using near-infrared (H-band) high-contrast polarimetry data from Subaru/HiCIAO and sub-millimeter CO (J=2-1) line emission data from ALMA. Both the near-infrared and sub-millimeter observations reveal several clear structures extending to $\sim$240 AU from the stars. Based on these observations at different wavelengths, we report the following discoveries. One arm-like structure detected in the near-infrared band initially extends from the south of the binary with a subsequent turn to the northeast, corresponding to two bar-like struct…
We present hydrodynamical simulations to model the accretion flow from a polar circumbinary disc onto a high eccentricity ($e=0.78$) binary star system with near unity mass ratio ($q=0.83$), as a model for binary HD 98800 BaBb. We compare the polar circumbinary disc accretion flow with the previously studied coplanar case. In the coplanar case, the circumbinary disc becomes eccentric and the accretion alternates from being dominant onto one binary member to the other. For the polar disc case involving a highly eccentric binary, we find that the circumbinary disc retains its initially low eccen…
In the present study we aim to investigate the circumstellar environment of the spectroscopic binary T Tauri star CS Cha. From unresolved mid- to far-infrared photometry it is predicted that CS Cha hosts a disk with a large cavity. In addition, SED modeling suggests significant dust settling, pointing towards an evolved disk that may show signs of ongoing or completed planet formation. We observed CS Cha with the high contrast imager VLT/SPHERE in polarimetric differential imaging mode to resolve the circumbinary disk in near infrared scattered light. These observations were followed-up by VLT…
A large fraction of stars is found to be part of binary or higher-order multiple systems. The ubiquity of planets found around single stars raises the question if and how planets in binary systems may form. Protoplanetary disks are the birthplaces of planets, and their characterization is crucial in order to understand the planet formation process. Our aim is to characterize the morphology of the GG Tau A disk, one of the largest and most massive circumbinary disks, and trace evidence for binary-disk interactions. We obtained observations in polarized scattered light of GG Tau A using the SPHE…
Near-Infrared Imaging Polarimetry of Inner Region of GG Tau A Disk
通过使用Subaru/HiCIAO进行无掩模偏振成像，在$H$波段成功探测到GG Tau A系统周围盘内部区域的偏振散射光，空间分辨率约为0.07 $\arcsec$，揭示了这颗年轻双星周围复杂的内部盘结构。本文报告了在GG Tau Ab以北观测到的弧形结构和在GG Tau Aa周围延伸到距离主星约28 AU的拱星结构的一部分。GG Tau Ab周围的斑点噪声将其盘半径限制为<13 AU。根据环联星环的大小和围绕着GG Tau Aa的星周盘，联星轨道的半长轴可能是62天文单位。目前的观测结果与以前的ALMA和近红外（NIR）H $_2$发射观测结果的比较表明，北弧可能是一个大的流光的一部分，从环联星环流动，以维持拱星盘。根据先前的研究，GG Tau Aa周围的拱星盘有足够的质量，可以维持足够的时间来行星形成;因此，我们的研究表明，行星可以在近距离（距离$\lesssim$ 100 AU）的年轻双星系统中形成。
This work is part of a multi-wavelength program to study the effects of X-ray/UV/optical stellar radiation on the chemistry of the circumbinary disk around the young high-eccentricity binary DQ Tau. ALMA observations for near/around December 5, 2021 periastron were postponed due to bad weather, but supporting Swift-XRT-UVOT TOO observations were successful. These Swift observations along with previous X-ray-optical-mm data show that DQ Tau keeps exhibiting powerful flares near periastron, offering a unique laboratory for studies of flare effects on the gas-phase ion chemistry in protoplanetary…
All four circumbinary (CB) protoplanetary disks orbiting short-period ($P < 20$ day) double-lined spectroscopic binaries (SB2s)---a group that includes UZ Tau E, for which we present new ALMA data---exhibit sky-plane inclinations $i_{\rm disk}$ which match, to within a few degrees, the sky-plane inclinations $i_\star$ of their stellar hosts. Although for these systems the true mutual inclinations $θ$ between disk and binary cannot be directly measured because relative nodal angles are unknown, the near-coincidence of $i_{\rm disk}$ and $i_\star$ suggests that $θ$ is small for these most compac…
DQ Tau is a young low-mass spectroscopic binary, consisting of two almost equal-mass stars on a 15.8 day period surrounded by a circumbinary disk. We analyzed DQ Tau's light curves obtained by Kepler K2, the Spitzer Space Telescope, and ground-based facilities. We observed variability phenomena, including rotational modulation by stellar spots, energetic stellar flares, brightening events around periastron due to increased accretion, and short dips due to temporary circumstellar obscuration. The study on DQ Tau will help in discovering and understanding the formation and evolution of other rea…
We analyze the highest-resolution millimeter continuum and near-infrared (NIR) scattered-light images presented to date of the circumbinary disk orbiting V4046 Sgr, a ~20 Myr old actively accreting, close binary T Tauri star system located a mere 72.4 pc from Earth. We observed the disk with the Atacama Large Millimeter/submillimeter Array (ALMA) at 870-micron during Cycle 4, and we analyze these data in conjunction with archival NIR (H band) polarimetric images obtained with SPHERE/IRDIS on the ESO Very Large Telescope. At 0.3'' (20 au) resolution, the 870-micron image reveals a marginally re…
IRAS~04158+2805 has long been thought to be a very low mass T-Tauri star (VLMS) surrounded by a nearly edge-on, extremely large disc. Recent observations revealed that this source hosts a binary surrounded by an extended circumbinary disc with a central dust cavity. In this paper, we combine ALMA multi-wavelength observations of continuum and $^{12}$CO line emission, with H$α$ imaging and Keck astrometric measures of the binary to develop a coherent dynamical model of this system. The system features an azimuthal asymmetry detected at the western edge of the cavity in Band~7 observations and a…
A Pre-Main Sequence Binary Viewed Through its Circumbinary Disk: A New Phase for KH 15D
Dickinson College（迪金森学院）；Tufts University（塔夫茨大学）；Space Telescope Science Institute（太空望远镜科学研究所）；Rensselaer Polytechnic Institute（伦斯勒理工学院）；Wesleyan University（卫斯理安大学）；University of Kent（肯特大学）；Lowell Observatory（洛厄尔天文台）；American Association of Variable Star Observers（变星观测者美国协会）；Thüringer Landessternwarte（图林根州立天文台）
We present high spatial resolution observations of the continuum emission from the young multiple star system UZ Tau at frequencies from 6 to 340 GHz. To quantify the spatial variation of dust emission in the UZ Tau E circumbinary disk, the observed interferometric visibilities are modeled with a simple parametric prescription for the radial surface brightnesses at each frequency. We find evidence that the spectrum steepens with radius in the disk, manifested as a positive correlation between the observing frequency and the radius that encircles a fixed fraction of the emission ($R_{eff} \prop…
We conducted high-contrast polarimetry observations of T Tau in the H-band, using the HiCIAO instrument mounted on the Subaru Telescope, revealing structures as near as 0.$\arcsec$1 from the stars T Tau N and T Tau S. The whole T Tau system is found to be surrounded by nebula-like envelopes, and several outflow-related structures are detected in these envelopes. We analyzed the detailed polarization patterns of the circumstellar structures near each component of this triple young star system and determined constraints on the circumstellar disks and outflow structures. We suggest that the nearl…
The Effect of X-Ray and Accretion Variability on Mid-Infrared Lines in the Young Disk-Bearing Binary DQ Tau
The Pennsylvania State University（宾夕法尼亚州立大学）；Center for Exoplanets and Habitable Worlds, Penn State University（系外行星与宜居世界中心，宾夕法尼亚州立大学）；Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台，匈牙利研究网络天文学与地球科学研究中心）；Zentrum für Astronomie der Universität Heidelberg（海德堡大学天文学中心）；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Institute of Astronomy, Russian Academy of Sciences（俄罗斯科学院天文学研究所）；Institute of Physics and Astronomy, ELTE Eötvös Loránd University（罗兰大学物理与天文学研究所）；Centre for Astrophysics Research, University of Hertfordshire（赫特福德大学天体物理学研究中心）
