The role of bipolar jets in the formation of stars, and in particular how they are launched, is still not well understood. We probe the protostellar jet launching mechanism, via high resolution observations of the near-IR [FeII] 1.53,1.64 micron lines. We consider the bipolar jet from the Classical T Tauri star, DO Tau, & investigate jet morphology & kinematics close to the star, using AO-assisted IFU observations from GEMINI/NIFS. The brighter, blue-shifted jet is collimated quickly after launch. This early collimation requires the presence of magnetic fields. We confirm velocity asymmetries between the two jet lobes, & confirm no time variability in the asymmetry over a 20 year interval. This sustained asymmetry is in accordance with recent simulations of magnetised disk-winds. We examine the data for jet rotation. We report an upper limit on differences in radial velocity of 6.3 & 8.7 km/s for the blue & red-shifted jets, respectively. Interpreting this as an upper limit on jet rotation implies that any steady, axisymmetric magneto-centrifugal model of jet launching is constrained to a launch radius in the disk-plane of 0.5 & 0.3 au for the blue & red-shifted jets, respectively. This supports an X-wind or narrow disk-wind model. This pertains only to the observed high velocity [FeII] emission, & does not rule out a wider flow launched from a wider radius. We report detection of small amplitude jet axis wiggling in both lobes. We rule out orbital motion of the jet source as the cause. Precession can better account for the observations but requires double the precession angle, & a different phase for the counter-jet. Such non-solid body precession could arise from an inclined massive Jupiter companion, or a warping instability induced by launching a magnetic disk-wind. Overall, our observations are consistent with an origin of the DO Tau jets from the inner regions of the disk.
We compute successfully the launching of two magnetic winds from two circumbinary disks formed after a common envelope event. The launching is produced by the increase of magnetic pressure due to the collapse of the disks. The collapse is due to internal torques produced by a weak poloidal magnetic field. The first wind can be described as a wide jet, with an average mass-loss rate of $\sim 1.3 \times 10^{-7}$ \Moy\ and a maximum radial velocity of $\sim 230$ \kms. The outflow has a half-opening angle of $\sim 20^{\circ}$. Narrow jets are also formed intermittently with velocities up to 3,000 …
Several observations of stellar jets show evidence of X-ray emitting shocks close to the launching site. In some cases, the shocked features appear to be stationary, also for YSOs at different stages of evolution. We study the case of HH 154, the jet originating from the embedded binary Class 0/I protostar IRS 5, and the case of the jet associated to DG Tau, a more evolved Class II disk-bearing source or Classical T Tauri star (CTTS), both located in the Taurus star-forming region. We aim at investigating the effect of perturbations in X-ray emitting stationary shocks in stellar jets; the stab…
One of the outstanding problems in star-formation theory concerns the transfer of angular momentum such that mass can accrete onto a newly born young stellar object (YSO). From a theoretical standpoint, outflows and jets are predicted to play an essential role in angular momentum transfer and their rotation motions have been reported for both low- and high-mass YSOs. However, little quantitative discussion on outflow launching mechanisms have been presented for high-mass YSOs due to a lack of observational data. Here we present a clear signature of rotation in the bipolar outflow driven by Ori…
Brown Dwarf Jets: Investigating the Universality of Jet Launching Mechanisms at the Lowest Masses
最近，它已成为明显的原恒星一样的外流活动延伸到棕矮星（BD）的质量制度。虽然吸积的存在似乎是所有已知驱动喷流的物体的共同成分，但基本问题仍然没有答案。更突出的是喷气式飞机发射的确切机制，以及这种机制在如此多样的来源和规模中是否仍然具有普遍性。为了解决这些问题，我们一直在调查流出活动的原恒星物体的样本，在质量和质量吸积率有很大的不同。其中的核心是我们对褐矮星喷流的研究。到目前为止，经典金牛座T星（CTTS）为我们提供了解码发射机制的最佳试金石。在这里，我们将总结到目前为止所了解的BD喷流和重要的约束条件的观察可以放置在模型上。我们将着重于比较中心质量小于0.1 M \odot的物体驱动的喷流和CTTS驱动的喷流。特别是，我们希望了解如何的质量流出吸积率的比例比较，已被测量的CTTS。
Sub-arcsecond high sensitivity measurements of the DG~Tau jet with e-MERLIN
我们提出了非常高的空间分辨率深射电连续观测5 GHz（6厘米）与e-MERLIN的年轻恒星DG Tau A和B。假设它是从非常接近（~=1天文单位）的恒星发射，我们的研究结果表明，DG Tau A流出最初开始作为一个不良集中的风，并经历了显着的准直进一步沿喷流（~=50天文单位）。我们推导出了DG Tau A的喷流参数，发现在距离源2天文单位的范围内，初始喷流张开角为86度，喷流电离成分的质量损失率为1.5 × 10 ^-8太阳质量/年，总的喷射/吸积比在0.06 ~ 0.3之间。这些结果与磁流体喷气发射理论的预测是一致的。
We present high angular resolution ($\sim$0.94$"$) $^{12}$CO(1-0) Atacama Large Millimeter/Submillimeter Array (ALMA) observations obtained during the 2014 long baseline campaign from the eruptive bipolar flow from the multiple XZ Tau stellar system discovered by the Hubble Space Telescope (HST). These observations reveal, for the first time, the kinematics of the molecular flow. The kinematics of the different ejections close to XZ Tau reveal a rotating and expanding structure with a southeast-northwest velocity gradient. The youngest eruptive bubbles unveiled in the optical HST images are in…
Sternberg Astronomical Institute, M.V. Lomonosov Moscow State University（列别捷夫天文研究所，莫斯科国立大学）；Faculty of Physics, M.V. Lomonosov Moscow State University（莫斯科国立大学物理系）
We use 3D hydrodynamical numerical simulations and show that jittering bipolar jets that power core-collapse supernova (CCSN) explosions channel further accretion onto the newly born neutron star (NS) such that consecutive bipolar jets tend to be launched in the same plane as the first two bipolar jet episodes. In the jittering-jets model the explosion of CCSNe is powered by jittering jets launched by an intermittent accretion disk formed by accreted gas having a stochastic angular momentum. The first two bipolar jets episodes eject mass mainly from the plane defined by the two bipolar axes. A…
Spatially resolved mid-infrared observations of the triple system T Tauri
为了提高我们的知识的特点和分布的拱星尘埃与年轻的层次三重系统T头的各个组成部分，在N-波段的观测与VLTI进行。我们的研究是基于干涉和分光光度测量，并辅以新的视觉和红外光度。此外，相位进行了研究，以确定在近南双星中占主导地位的中红外光源。这些数据是在一个复杂的物理磁盘模型的帮助下拟合的。该模型利用基于蒙特卡罗方法的辐射转移代码MC 3D。在系统的所有三个组件周围都发现了扩展的中红外发射。同时配合测光和干涉测量数据证实了一个几乎面对拱盘周围的T头N的图片。朝向这颗恒星，在发射中可以看到硅酸盐带。这个发射特征被用来模拟星周盘的尘埃含量。在T Tau S附近，在吸收中可以看到硅酸盐带。这种吸收对红外伴星T Tau Sa非常明显，这可以从两个南部分量的第一个单独的N带光谱中看出。我们的配合支持以前的建议，一个几乎边缘上的光盘是目前围绕T头萨。因此，这个圆盘相对于T Tau N周围的拱星圆盘没有对准。干涉测量数据表明，磁盘T头萨周围是面向南北方向，这有利于这个源作为发射场的东西射流。我们进一步确定从干涉数据的相对位置的组件的南方二进制。
Context. Red supergiant stars are one of the latest stages in the evolution of massive stars. Their photospheric convection may play an important role in the launching mechanism of their mass loss; however, its characteristics and dynamics are still poorly constrained. Aims. By observing red supergiant stars with near infrared interferometry at different epochs, we expect to reveal the evolution of bright convective features on their stellar surface. Methods. We observed the M2Iab-Ib red supergiant star CE Tau with the VLTI/PIONIER instrument in the H band at two different epochs separated by …
FS Tau B是为数不多的拥有喷流和反喷流以及光学可见空腔壁的金牛座T星之一。我们利用Subaru/IRCS获得了它的喷流-腔体系统在近红外H和K波段的图像和光谱，并首次在[Fe II] 1.644 μm谱线上探测到了喷流和反喷流。在内部2”内，蓝移喷流更亮，而超过~ 5”，红移反喷流主导[Fe II]发射。最里面的蓝移结在光谱上分辨为~ 110 km/s的大线宽，而最里面的红移结在光谱上分辨不出来。喷流与反喷流的速度比约为1.34，这表明FS Tau B正在驱动一个不对称的喷流，类似于在几颗金牛座T星中发现的喷流。结合文献中的光学观测，我们发现蓝移喷流比红移喷流具有更低的密度和更高的激发。我们认为，亮度和速度的不对称性是双极外流驱动在不同的质量损失率，同时保持平衡的线动量的表现。对FS Tau B系统中不对称性的充分解释有待于详细建模和对与风相关的空腔壁的运动学结构的进一步研究。
One of the major puzzles in the study of stellar evolution is the formation process of bipolar and multi-polar planetary nebulae. There is growing consensus that collimated jets create cavities with dense walls in the slowly-expanding (10--20 ~km~s$^{-1}$) envelope ejected in previous evolutionary phases, leading to the observed morphologies. However, the launching of the jet and the way it interacts with the circumstellar material to create such asymmetric morphologies have remained poorly known. Here we present for the first time CO emission from the asymptotic giant branch star W43A that tr…
Modeling YSO Jets in 3D II: Accretion-Fed, Star-Anchored Poynting Jets in the Low-Density Polar Cavity Powered by Disk-Magnetosphere Interaction
University of Virginia（弗吉尼亚大学）；Virginia Institute of Theoretical Astronomy, University of Virginia（弗吉尼亚大学理论天体物理研究所）；University of Nevada, Las Vegas（内华达大学拉斯维加斯分校）；Nevada Center for Astrophysics, University of Nevada, Las Vegas（内华达大学拉斯维加斯分校内华达天体物理学中心）；University of Florida（佛罗里达大学）
DG Tau B是一个I类年轻恒星源，驱动着不对称的HH 159双极喷流。在可见光波段，它被星周光学厚度的物质所遮蔽。使用VLA和JVLA观测，我们确定了第一次这个源的自行，并发现它们是一致的，误差范围内，与附近的年轻恒星DG头。我们还讨论了一个喷射事件，这是明显的，在1994年的VLA数据。作为光学和分子外流，这种喷射跟踪在无线电连续谱是显着不对称的，只检测到的西北部的恒星。我们建议，这个结，不再检测到的无线电，可以观察到在未来的光学图像的DG头B。VLA源和附近红外目标的位置不重合，我们认为VLA源跟踪激发目标，而红外源可能是反射波瓣。
Jets are rarely associated with pre-main-sequence intermediate-mass stars. Optical and near-IR observations of jet-driving sources are often hindered by the presence of a natal envelope. Jets around partly embedded sources are a useful diagnostic to constrain the geometry of the concealed protoplanetary disk. In fact, the jet-driving mechanisms are affected by both spatial anisotropies and episodic variations at the (sub-)au scale from the star. We obtained a rich set of high-contrast VLT/SPHERE observations from 0.6 micron to 2.2 micron of the young intermediate-mass star RY Tau. Given the pr…
Global simulations of accretion flows onto perturbers embedded in magnetized disks -I. MRI and jet formation in ideal MHD
Charles University（查理大学）；Instituto de Astronomía, Universidad Nacional Autónoma de México（墨西哥国立自治大学天文研究所）；Niels Bohr International Academy, Niels Bohr Institute（尼尔斯·玻尔国际学院，尼尔斯·玻尔研究所）
We present VRIJHK photometry of the KH 15D T Tauri binary system for the 2015/16 and 2016/17 observing seasons. For the first time in the modern (CCD) era we are seeing Star B fully emerge from behind the trailing edge of the precessing circumbinary ring during each apastron passage. We are, therefore, able to measure its luminosity and color. Decades of photometry on the system now allow us to infer the effective temperature, radius, mass and age of each binary component. We find our values to be in good agreement with previous studies, including archival photographic photometry from the era …
Outflowing motions, whether a wind launched from the disk, a jet launched from the protostar, or the entrained molecular outflow, appear to be an ubiquitous feature of star formation. These outwards motions have a number of root causes, and how they manifest is intricately linked to their environment as well as the process of star formation itself. Using the ALMA Science Verification data of HL Tau, we investigate the high velocity molecular gas being removed from the system as a result of the star formation process. We aim to place these motions in context with the optically detected jet, and…
The mechanism for jet formation in the disks of T Tauri stars is poorly understood. Observational benchmarks to launching models can be provided by tracing the physical properties of the kinematic components of the wind and jet in the inner 100 au of the disk surface. In the framework of the GHOsT (GIARPS High-resolution Observations of T Tauri stars) project, we aim to perform a multi-line analysis of the velocity components of the gas in the jet acceleration zone. We analyzed the GIARPS-TNG spectra of six objects in the Taurus-Auriga complex (RY Tau, DG Tau, DL Tau, HN Tau, DO Tau, RW Aur A)…
For the active T-Taur star RW Aur A we have performed long-term (~10 yr) monitoring observations of (1) jet imaging in the [Fe II] 1.644-micron emission line using Gemini-NIFS and VLT-SINFONI; (2) optical high-resolution spectroscopy using CFHT-ESPaDOnS; and (3) V-band photometry using the CrAO 1.25-m telescope and AAVSO. The latter two observations confirm the correlation of time variabilities between (A) the Ca II 8542 A and O I 7772 A line profiles associated with magnetospheric accretion, and (B) optical continuum fluxes. The jet images and their proper motions show that four knot ejection…
The origin of outflows and their exact impact on disk evolution and planet formation remain crucial open questions. DG Tau B is a Class I protostar associated with a rotating conical CO outflow and a structured disk. Hence it is an ideal target to study these questions. We aim to characterize the morphology and kinematics of the DG Tau B outflow in order to elucidate its origin and potential impact on the disk. Our analysis is based on Atacama Large Millimeter Array (ALMA) 12CO(2-1) observations of DG Tau B at 20 au angular resolution. We characterize three different types of substructures in …
We present results from a survey searching for spatially resolved near-infrared line emission from molecular hydrogen gas in the circumstellar environments of nine young stars: AA Tau, AB Aur, DoAr 21, GG Tau, GM Aur, LkCa 15, LkH$α$ 264, UY Aur, and V773 Tau. Prior high-resolution spectra of these stars showed the presence of ro-vibrational H$_2$ line emission at 2.12$μ$m with characteristics more typical of gas located in proto-planetary disks rather than outflows. In this study, we spatially resolve the H$_2$ emission in the eight stars where it is detected. LkCa 15 is the only target that …
We have performed an unbiased search for outflows from young stars in Cygnus-X using 42 deg$^2$ of data from the UKIRT Widefield Infrared Survey for H$_2$ (UWISH2 survey), to identify shock-excited near-IR H$_2$ emission in the 1$-$0 S(1) 2.122 $μ$m line. We uncovered 572 outflows, of which 465 are new discoveries, increasing the number of known objects by more than 430%. This large and unbiased sample allows us to statistically determine the typical properties of outflows from young stars. We found 261 bipolar outflows and 16% of these are parsec-scale. The typical bipolar outflow is 0.45pc i…
Forbidden neon emission from jets of low-mass young stars can be used to probe the underlying high-energy processes in these systems. We analyze spectra of the jet of DG Tau obtained with the Very Large Telescope/X-Shooter spectrograph in 2010. [Ne III] $λ$3869 is clearly detected in the innermost 3" microjet and the outer knot located at $\sim$6".5. The velocity structure of the inner microjet can be decomposed into the low-velocity component (LVC) at $\sim -70$ km/s and the high-velocity component (HVC) at $\sim -180$ km/s. Based on the observed [Ne III] flux and its spatial extent, we sugge…
Kinematic signatures of the jet, winds, multicavities, and episodic shells arising in the unified model of bipolar outflows developed in Shang et al.\ (2020), in which an outflow forms by radially directed, wide-angle toroidally magnetized winds interacting with magnetized isothermal toroids, are extracted in the form of position--velocity diagrams. Elongated outflow lobes, driven by magnetized winds and their interplay with the environment, are dominated by extended bubble structures with mixing layers beyond the conventional thin-shell models. The axial cylindrically stratified density jet c…
ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT) VII: the layered molecular outflow from HL Tau and its relationship with the ringed disk
Context. Protoplanetary disks around young stars often contain substructures like rings, gaps, and spirals that could be caused by interactions between the disk and forming planets. Aims. We aim to study the young (1-3 Myr) star DR Tau in the near-infrared and characterize its disk, which was previously resolved through sub-millimeter interferometry with ALMA, and to search for possible sub-stellar companions embedded into it. Methods. We observed DR Tau with VLT/SPHERE both in polarized light (H broad band) and total intensity (in Y, J, H, and K spectral bands). We also performed L' band obse…
We analyse recent high-quality Atacama Large Millimeter Array (ALMA) molecular line mapping observations of the northeast jet of the young stellar object (YSO) OMC 2/FIR6b (HOPS-60) and find that these ALMA observations are much more likely to indicate a twin-jet structure than jet rotation, as previously hypothesized. The interpretation of the line of sight velocity gradient across (perpendicular to its axis) the northeast jet of Fir6b in terms of jet rotation leads to jet-launching radii of ~2-3AU. However, the velocities of the jets ~100-400 km/s are much larger than the escape speed from t…
Young stars accrete mass from circumstellar disks and in many cases, the accretion coincides with a phase of massive outflows, which can be highly collimated. Those jets emit predominantly in the optical and IR wavelength range. However, in several cases X-ray and UV observations reveal a weak but highly energetic component in those jets. X-rays are observed both from stationary regions close to the star and from knots in the jet several hundred AU from the star. In this article we show semi-analytically that a fast stellar wind which is recollimated by the pressure from a slower, more massive…
Highly collimated parsec-scale jets, generally linked to the presence of an accretion disk, are a commonly observed phenomenon from revealed low-mass young stellar objects. In the past two decades, only a very few of these objects have been directly (or indirectly) observed towards high-mass (M > 8 M$_{\odot}$) young stellar objects, adding to the growing evidence that disk-mediated accretion is a phenomenon also occurring in high-mass stars, the formation mechanism of which is still poorly understood. Of the observed jets from massive young stars, none is in the optical regime (due to these b…
We present 12CO (J=2-1) sensitive molecular line and 1.3 mm continuum observations made with the Submillimeter Array (SMA) of the bipolar outflow associated with the young star located in the Bok globule known as CB 26. The SMA observations were carried out in its extended configuration allowing us to study the kinematics and structure of the outflow with about 1 arcsec or 140 au resolution. We find that the dusty and edge-on circumstellar disk related with the outflow has an projected spatial (deconvolved) size of 196 au x 42 au with a total (gas and dust) mass of 0.031 Msun. We estimated a d…
Recently, differences in Doppler shifts across the base of four close classical T Tauri star jets have been detected with the HST in optical and near-ultraviolet (NUV) emission lines, and these Doppler shifts were interpreted as rotation signatures under the assumption of steady state flow. To support this interpretation, it is necessary that the underlying disks rotate in the same sense. Agreement between disk rotation and jet rotation determined from optical lines has been verified in two cases and rejected in one case. Meanwhile, the NUV lines, which may trace faster and more collimated inn…
