13C17O suggests gravitational instability in the HL Tau disc

与公牛一同奔跑：金牛座恒星形成区中恒星-原行星盘相遇的频率

Running with the Bulls: The frequency of star-disc encounters in the Taurus star forming region

本研究针对金牛座恒星形成区恒星-原行星盘相遇事件的频率问题，构建含双星与空间运动学子结构的动力学模型开展演化模拟，量化了不同强度截断事件的发生速率，并指出现有观测样本可能不完整，新增观测案例或暗示新物理机制。

High resolution millimetre imaging of the CI Tau protoplanetary disc - a massive ensemble of protoplanets from 0.1 - 100 au

We present high resolution millimeter continuum imaging of the disc surrounding the young star CI Tau, a system hosting the first hot Jupiter candidate in a protoplanetary disc system. The system has extended mm emission on which are superposed three prominent annular gaps at radii ~ 13, 39 and 100 au. We argue that these gaps are most likely to be generated by massive planets so that, including the hot Jupiter, the system contains four gas giant planets at an age of only 2 Myr. Two of the new planets are similarly located to those inferred in the famous HL Tau protoplanetary disc; in CI Tau, …

Evidence of a past disc-disc encounter: HV and DO Tau

Theory and observations suggest that star formation occurs hierarchically due to the fragmentation of giant molecular clouds. In this case we would expect substructure and enhanced stellar multiplicity in the primordial cluster. This substructure is expected to decay quickly in most environments, however historic stellar encounters might leave imprints in a protoplanetary disc (PPD) population. In a low density environment such as Taurus, tidal tails from violent star-disc or disc-disc encounters might be preserved over time-scales sufficient to be observed. In this work, we investigate the po…

Magnetic field gradient effects on the magnetorotational instability

The magnetorotational instability (MRI), also known as the Balbus -- Hawley instability, is thought to have an important role on the initiation of turbulence and angular momentum transport in accretion discs. In this work, we investigate the effect of the magnetic field gradient in the azimuthal direction on MRI. We solve the magnetohydrodynamic equations by including the azimuthal component of the field gradient. We find the dispersion relation and calculate the growth rates of the instability numerically. The inclusion of the azimuthal magnetic field gradient produces a new unstable region o…

TNG XLVII的GAPS项目：V1298 Tau不寻常的形成历史

The GAPS program at TNG XLVII: The unusual formation history of V1298 Tau

本研究通过N体模拟与NAMD分析，探究年轻恒星V1298 Tau两颗外侧巨行星的高密度成因及系统动力学状态，提出系统经会聚迁移与共振俘获形成、行星散射打破共振链的演化情景。

Effects of Dust Evolution on the Vertical Shear Instability in the Outer Regions of Protoplanetary Disks

The vertical shear instability (VSI) is a hydrodynamical instability that requires rapid gas cooling and has been suggested to operate in outer regions of protoplanetary disks. The VSI drives turbulence with strong vertical motions, which could regulate the dust growth and settling. However, dust growth and settling can regulate the VSI because dust depletion makes gas cooling inefficient in outer disk regions that are optically thin to their own thermal emission. In this study, we quantify this potentially stabilizing effects of dust evolution on the VSI based on the linear analysis. We const…

V892 Tau：三合星系统中受潮汐扰动的环双星盘

V892 Tau: A tidally perturbed circumbinary disc in a triple stellar system

本文通过ALMA高分辨率观测与流体动力学模拟，揭示V892 Tau环双星盘的非开普勒特征源于伴星V892 Tau NE的错位偏心轨道（偏心率0.2-0.5，相互倾角30°-60°），并指出该构型将危及盘外区未来行星的稳定性。

Demographics of Transition Discs in Ophiuchus and Taurus

Transition disc systems are young stars that appear to be on the verge of dispersing their protoplanetary discs. We explore the nature of these systems by comparing the stellar accretion rates and disc masses of transition discs and normal T Tauri stars in Taurus and Ophiuchus. After controlling for the known dependencies of stellar accretion rate and disc mass and on age, stellar accretion rate on stellar mass, and disc mass on the presence of stellar or sub-stellar companions, we find that the normal T Tauri stars show a trend of stellar accretion rate increasing with disc mass. The transiti…

Global 3D Simulations of Disc Accretion onto the classical T Tauri Star BP Tauri

The magnetic field of the classical T Tauri star BP Tau can be approximated as a superposition of dipole and octupole moments with respective strengths of the polar magnetic fields of 1.2 kG and 1.6 kG (Donati et al. 2008). We adopt the measured properties of BP Tau and model the disc accretion onto the star. We observed in simulations that the disc is disrupted by the dipole component and matter flows towards the star in two funnel streams which form two accretion spots below the dipole magnetic poles. The octupolar component becomes dynamically important very close to the star and it redirec…

Dynamics of wind and the dusty environments in the accreting T Tauri stars RY Tau and SU Aur

Classical T Tauri stars with ages of less than 10 Myr possess accretion discs. Magnetohydrodynamic processes at the boundary between the disc and the stellar magnetosphere control the accretion and ejections gas flows. We carried out a long series of simultaneous spectroscopic and photometric observations of the classical T Tauri stars RY Tau and SU Aur with the aim to quantify the accretion and outflow dynamics at time scales from days to years. It is shown that dust in the disc wind is the main source of photometric variability of these stars. In RY Tau we observed a new effect: during event…

Orbital parameters and activity of ZZ Tau -- a low mass young binary with circumbinary disc

We present the results of our new observations of the young binary ZZ Tau with a circumbinary disc. The system was found to consist of two coeval (age $<2$ Myr) classical T Tauri stars with the total mass $0.86 \pm 0.09$ M$_\odot$, orbital period $46.8 \pm 0.8$ yr, semimajor axis $88.2 \pm 2.1$ mas, eccentricity $0.58 \pm 0.02$ and the orbital inclination $123.^{\rm o} 8 \pm 1.^{\rm o} 0.$ The accretion rate of ZZ Tau A and ZZ Tau B are approximately $7\times 10^{-10}$ and $2\times 10^{-10}$ M$_\odot$ yr$^{-1},$ respectively. No correlation was found between the long-term photometric variabili…

Line and continuum radiative transfer modelling of AA Tau

We present photometric and spectroscopic models of the Classical T Tauri star AA Tau. Photometric and spectroscopic variability present in observations of AA Tau is attributed to a magnetically induced warp in the accretion disc, periodically occulting the photosphere on an 8.2--day timescale. Emission line profiles show signatures of both infall, attributed to magnetospherically accreting material, and outflow. Using the radiative transfer code TORUS, we have investigated the geometry and kinematics of AA Tau's circumstellar disc and outflow, which is modelled here as a disc wind. Photometric…

Spatially resolved mid-infrared observations of the triple system T Tauri

To enhance our knowledge of the characteristics and distribution of the circumstellar dust associated with the individual components of the young hierarchical triple system T Tau, observations in the N-band with MIDI at the VLTI were performed. Our study is based on both the interferometric and the spectrophotometric measurements and is supplemented by new visual and infrared photometry. Also, the phases were investigated to determine the dominating mid-infrared source in the close southern binary. The data were fit with the help of a sophisticated physical disc model. This model utilises the …