A5057163770- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Molecular Spectroscopy and Structure
- Solar and Space Plasma Dynamics
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Advanced Chemical Physics Studies
- Atmospheric Ozone and Climate
- Pulsars and Gravitational Waves Research
- Geomagnetism and Paleomagnetism Studies
- Planetary Science and Exploration
- Atomic and Molecular Physics
- Astronomical Observations and Instrumentation
- Radio Astronomy Observations and Technology
- Mass Spectrometry Techniques and Applications
- Galaxies: Formation, Evolution, Phenomena
- High-pressure geophysics and materials
- Advanced Combustion Engine Technologies
- Ionosphere and magnetosphere dynamics
- Fluid Dynamics and Turbulent Flows
- Quantum, superfluid, helium dynamics
- Laser-induced spectroscopy and plasma
Third Affiliated Hospital of Zhengzhou University
2025
Institute of Astronomy and Astrophysics, Academia Sinica
2015-2024
Academia Sinica
2005-2019
Institute of Earth Sciences, Academia Sinica
2018
Vatican Secret Archives
2013
Nanjing Library
2013
National Center for Theoretical Sciences
2006
National Tsing Hua University
2006
University of California, Berkeley
1995-2002
Center for Astrophysics Harvard & Smithsonian
2001-2002
The chondrules, calcium-aluminum-rich inclusions (CAIs), and rims in chondritic meteorites could be formed when solid bodies are lifted by the aerodynamic drag of a magnetocentrifugally driven wind out relative cool shaded disk close to star into heat direct sunlight. For reasonable self-consistent parameters bipolar outflow, base peak temperatures reached resemble those needed melt CAIs chondrules. process also yields natural sorting mechanism that explains size distribution as well their...
Protostars emit more x-rays, hard and soft, than young sunlike stars in advanced stages of formation. The x-ray emission becomes harder stronger during flares. excess x-rays may arise as a result the time-dependent interaction an accretion disk with magnetosphere central star. Flares produced by such fluctuations have important implications for x-wind model protostellar jets, flash-heating chondrules found chondritic meteorites, production short-lived radioactivities through bombardment...
Examples of calcium-aluminum-rich inclusions (CAIs) surrounded by thick chondrule mantles have been found in chondritic meteorites and cast doubt on the conventional belief that CAIs chondrules possessed different spacetime origins primitive solar nebula. We study specific processes which such objects, more common ordinary chondrules, might formed flare heating rocks interior to inner edge a gaseous accretion disk has truncated magnetized funnel flow onto central proto-Sun. Motivated...
We have analyzed a number of intense X-ray flares observed in the Chandra Orion Ultradeep Project (COUP), 13 days observation Nebula Cluster (ONC). Analysis flare decay allows to determine size, peak density and magnetic field flaring structure. A total 32 events (the most powerful 1% COUP flares), sufficient statistics for analysis. broad range times (from 10 400 ks) are present sample. Peak temperatures often very high, with half sample showing excess 100 MK. Significant sustained heating...
Calcium-aluminum-rich inclusions (CAIs) and chondrules of chondritic meteorites may originate with the melting dustballs launched by a magnetically driven bipolar outflow from inner edge primitive solar nebula. Bombardment protostellar cosmic rays make rock precursors CAIs radioactive, producing radionuclides found in that are difficult to obtain other mechanisms. Reasonable scalings observed hard X-rays for cosmic-ray protons released flares young stellar objects yield correct amounts...
We consider the asymptotic behavior of magnetocentrifugally driven X-winds, taking into proper account pressure balance across interface between open stellar field lines dead zone devoid matter and wind. At large distances from source outflow collimates jets along rotation axis. Being almost cylindrically symmetric even close to outflow, density distribution appears more jetlike than collection streamlines, which always contains a few members that skim over surface disk.
We study the effects of self-shielding in X-wind model protosolar cosmic-ray irradiation early solar-system rocks. adopt a two-component picture protoCAIs consisting cores with elemental abundances type B1 CAIs (calcium-aluminum-rich inclusions) and mantles less refractory material. The have power-law distribution sizes between Rmin Rmax. uniform thickness, whose value is chosen to bring total inventory elements at least as sulfur cosmic for entire population protoCAIs. Each object...
In January 2003, the Chandra Orion Ultradeep Project (COUP) detected about 1400 young stars during a 13.2 day observation of Nebula Cluster (ONC). This paper studies well-defined sample 28 solar-mass COUP sources to characterize magnetic activity analogs Sun and thereby improve understanding effects solar X-rays on nebula era planet formation. We find that active Suns spend 70% their time in characteristic state with relatively constant flux magnetically confined plasma temperatures kT_2 =...
Dense, star-forming cores of molecular clouds are observed to be significantly magnetized. A realistic magnetic field moderate strength has been shown suppress, through catastrophic braking, the formation a rotationally supported disk (RSD) during protostellar accretion phase low-mass star in ideal MHD limit. We address, two-dimensional (axisymmetric) simulations, question whether levels non-ideal effects, computed with simplified chemical network including dust grains, can weaken braking...
Stars form in dense cores of molecular clouds that are observed to be significantly magnetized. In the simplest case a laminar (non-turbulent) core with magnetic field aligned rotation axis, both analytic considerations and numerical simulations have shown formation large, 102 AU scale, rotationally supported protostellar disk is suppressed by braking ideal MHD limit for realistic level magnetization. This theoretical difficulty forming disks termed "magnetic catastrophe." A possible...
It has been shown that a realistic level of magnetization dense molecular cloud cores can suppress the formation rotationally supported disk (RSD) through catastrophic magnetic braking in axisymmetric ideal MHD limit. In this study, we present conditions for RSDs non-ideal effects computed self-consistently from an equilibrium chemical network. We find removing standard MRN distribution large population very small grains (VSGs) ~10 $\AA$ to few 100 dominate coupling bulk neutral matter field...
Radial substructures in circumstellar disks are now routinely observed by ALMA. There is also growing evidence that disk winds drive accretion such disks. We show through 2D (axisymmetric) simulations rings and gaps develop naturally magnetically coupled disk-wind systems on the scale of tens au, where ambipolar diffusion (AD) dominant non-ideal MHD effect. In magnetic field matter moderately coupled, remains relatively laminar with radial electric current steepened AD into a thin layer near...
In order to compare the X-wind with observations, one needs be able calculate its thermal and ionization properties. We formulate physical basis for streamline-by-streamline integration of heat equations steady X-wind. addition well-known processes associated interaction stellar accretion funnel hot spot radiation wind, we include X-ray heating ionization, mechanical heating, a revised calculation ambipolar diffusion heating. The arises from fluctuations produced by star-disk interactions...
Two explanations exist for the short-lived radionuclides (T1/2 ≤ 5 Myr) present in solar system when calcium-aluminum-rich inclusions (CAIs) first formed. They originated either from ejecta of a supernova or by situ irradiation nebular dust energetic particles. With half-life only 53 days, 7Be is then key discriminant, since it can be made irradiation. Using same model developed earlier our group, we calculate yield 7Be. Within uncertainties associated mainly with nuclear cross sections,...
The protostellar jet driven by L1448C was observed in the SiO J = 8–7 and CO 3–2 lines, 350 GHz dust continuum at ∼1'' resolution with Submillimeter Array. A narrow from northern source L1448C(N) high-velocity CO. consists of a chain emission knots an inter-knot spacing ∼2'' (500 AU) semi-periodic velocity variation. These are likely to be internal bow shocks beam that were formed due periodic variation ejection period ∼15–20 yr. innermost pairs knots, which significant map but barely seen...
HH 211 is a nearby young protostellar system with highly collimated jet. We have mapped it in 352 GHz continuum, SiO (J = 8 − 7), and HCO+ 4 3) emission at up to ∼02 resolution the Submillimeter Array (SMA). The continuum source now resolved into two sources, SMM1 SMM2, separation of ∼ 84 AU. seen center jet, probably tracing (inner) dusty disk around protostar driving SMM2 southwest may trace an envelope-disk small binary companion. A flattened radius 80 AU perpendicular jet axis. Its...
Stars form in dense cores of molecular clouds that are observed to be significantly magnetized. A dynamically important magnetic field presents a significant obstacle the formation protostellar disks. Recent studies have shown braking is strong enough suppress rotationally supported disks ideal MHD limit. Whether non-ideal effects can enable disk remains unsettled. We carry out first study on how modified by Hall effect, least explored three star (the other two being ambipolar diffusion and...
HH 212 is a nearby (400 pc) Class 0 protostellar system showing several components that can be compared with theoretical models of core collapse. We have mapped it in 350 GHz continuum and HCO+ J=4-3 emission ALMA at up to ~ 0.4" resolution. A flattened envelope compact disk are seen around the central source, as before. The kinematics shows infalling small rotation (i.e., spiraling) into thus identified pseudodisk magnetized Also, rotating rotationally supported. In addition, account for...
In the earliest (so-called "Class 0") phase of Sun-like (low-mass) star formation, circumstellar disks are expected to form, feeding protostars. However, these difficult resolve spatially because their small sizes. Moreover, there theoretical difficulties in producing retarding effects magnetic fields on rotating, collapsing material "magnetic braking"). With Atacama Large Millimeter/submillimeter Array (ALMA), it becomes possible uncover and study them detail. HH 212 is a very young...
The metastable helium triplet in the near-infrared (10833{\AA}) is among most important probes of exoplanet atmospheres. It can trace their extended outer layers and constrain mass-loss. We use high-resolution spectropolarimeter SPIRou on CFHT to search for spectrally resolved atmospheres eleven exoplanets, ranging from warm mini-Neptunes hot Jupiters orbiting G, K, M dwarfs. Observations were obtained as part Legacy Survey complementary open-time programs. apply a homogeneous data reduction...
Abstract Kinematic signatures of the jet, winds, multicavities, and episodic shells arising in unified model bipolar outflows developed Shang et al. (Paper I), which an outflow forms by radially directed, wide-angle toroidally magnetized winds interacting with isothermal toroids, are extracted form position–velocity diagrams. Elongated lobes, driven their interplay environment, dominated extended bubble structures mixing layers beyond conventional thin-shell models. The axial cylindrically...
We have mapped the SiO J = 5-4 line at 217 GHz from HH 211 molecular outflow with Submillimeter Array (SMA). The high-resolution map (16 × 09) shows that emission comes central narrow jet along axis a width of ~08 (~250 AU) FWHM. consists chain knots separated by 3''-4'' (~1000 AU), and most counterparts in shocked H2 seen new, deep VLT near-infrared image outflow. A innermost pair been discovered just ±2'' star. ratio between data upper limits 1-0 Chandler & Richer suggests these...
We develop a unified model for molecular outflows in star formation. The incorporates essential features expected of the primary wind, which is thought to be driven magnetocentrifugally from close central stellar object, and ambient core material shaped by anisotropic magnetic support. wind modeled as toroidally magnetized fast outflow moving radially away origin, with an angle-dependent density distribution: dense axial jet surrounded more tenuous wide-angle X-wind model. If dynamically...
Disk formation in magnetized cloud cores is hindered by magnetic braking. Previous work has shown that for realistic levels of core magnetization, the field suppresses rotationally supported disks during protostellar mass accretion phase low-mass star both ideal MHD limit and presence ambipolar diffusion typical rates cosmic ray ionization. Additional effects, such as ohmic dissipation, Hall effect, outflow, are needed to weaken braking enable persistent, supported, disks. In this paper, we...