A5072094726- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Nuclear Physics and Applications
- Simulation and Modeling Applications
- Adaptive optics and wavefront sensing
- Mechanics and Biomechanics Studies
- Industrial Technology and Control Systems
- High-pressure geophysics and materials
- Radio Astronomy Observations and Technology
- Seismic Waves and Analysis
- Forest Biomass Utilization and Management
- Laser-Plasma Interactions and Diagnostics
- Higher Education and Teaching Methods
- Solar and Space Plasma Dynamics
- Educational Technology and Assessment
- Agricultural Engineering and Mechanization
- Ionosphere and magnetosphere dynamics
- Heat Transfer Mechanisms
- Education and Work Dynamics
Sun Yat-sen University
2018-2024
Xi'an Institute of Optics and Precision Mechanics
2022
Shanghai Astronomical Observatory
2022
Fujian Agriculture and Forestry University
2004-2017
Hebrew University of Jerusalem
2014-2016
Tel Aviv University
2014-2016
University of Toronto
2011-2014
The University of Texas at Austin
2006-2013
Chinese Academy of Sciences
2003-2005
Institute of High Energy Physics
2003-2005
Abstract When a star passes through the tidal disruption radius of massive black hole (BH), it can be torn apart by force BH, known as event (TDE). Since observed UV/optical luminosity significantly exceeds predictions compact disk model in classical TDE theory, two competing models, stream collision and envelope reprocessing, have been proposed to address this discrepancy. To distinguish between these we investigated continuum reverberation behaviors for ~30 TDEs with high-quality multiband...
Abstract We present and analyze the optical/UV X-ray observations of a nearby tidal disruption event (TDE) candidate, AT 2019azh, from ∼30 days before to ∼400 after its early optical peak. The X-rays show late brightening by factor ∼30–100 around 200 discovery, while UV/opticals continuously decayed. two flaring episodes variation, temporally uncorrelated with UV/opticals. found clear sign hardness evolution; i.e., source is harder at times becomes softer as it brightens later. drastically...
Abstract During the inspiralling of a white dwarf (WD) into an intermediate-mass black hole (∼10 2−5 M ⊙ ), both gravitational waves (GWs) and electromagnetic (EM) radiation are emitted. Once eccentric orbit’s pericenter radius approaches tidal radius, WD would be tidally stripped upon each passage. The accretion this mass produce EM radiation. It is suspected that recently discovered new types transients, namely quasiperiodic eruptions fast ultraluminous x-ray bursts, might originate from...
Abstract Close encounter between a star and supermassive black hole (SMBH) results in the tidal disruption of star, known as event (TDE). Recently, few TDEs, e.g., ASASSN-15oi AT2018hyz, have shown late-time (hundreds days after their UV/optical peaks) radio flares with luminosities 10 38∼39 erg s −1 . The super-Eddington fallback or accretion TDE may generate mass outflow. Here, we investigate scenario that come from interaction outflow circumnuclear gaseous clouds, addition to...
During a stellar tidal disruption event (TDE), an accretion disk forms as debris returns to the site and circularizes. Rather than being confined within circularizing radius, can spread larger radii conserve angular momentum. A spreading is source of matter for re-accretion at rates which exceed later fallback rate, although wind suppress its contribution central black hole rate. detectible through break in rate history, or, longer wavelengths, by own emission. We model evolution TDE size...
We compute the temporal profiles of gamma-ray burst pulse in four Burst and Transient Source Experiment (BATSE) Large Area Detector (LAD) discriminator energy channels, with relativistic curvature effect a expanding fireball being explicitly investigated. Assuming an intrinsic 'Band' shape spectrum energy-independent emission profile, we show that merely can produce detectable spectral lags if profile has gradually decaying phase. examine lag's dependences on some physical parameters, such...
Gamma-ray burst X-ray flares are believed to mark the late time activity of central engine. We compute temporal evolution average flare luminosity $< L >$ in common rest frame energy band 44 GRBs taken from large \emph{Swift} 5-years data base. Our work highlights importance a proper consideration threshold detection against contemporaneous continuous emission. In interval $30 \rm{s}<t<1000\,\rm{s}$ we find >\propto t^{-2.7\pm 0.1}$; this implies that isotropic scaling is...
Abstract We report the discovery of a tidal disruption event (TDE) candidate occurring in active galactic nucleus (AGN) SDSS J022700.77-042020.6. A sudden increase flux from J0227-0420 during second half 2009 appears long-term optical, UV, and near-IR (NIR) light curves. plateau phase, following an initial decline, is seen near-UV (NUV) optical find possible evidence that NUV band may lag behind ones by ∼70–80 days with also much shorter duration, is, ∼7–15 against ∼40–50 days. The...
Abstract Optical transient surveys have led to the discovery of dozens stellar tidal disruption events (TDEs) by massive black hole in centers galaxies. Despite extensive searches, X-ray follow-up observations produced no or only weak detections most them. Here we report delayed brightening around 140 days after optical outburst TDE OGLE16aaa, followed several flux dips during decay phase. These properties are unusual for standard TDEs and could be explained presence supermassive binary...
Tidal disruption events (TDEs) can uncover the quiescent supermassive black holes (SMBHs) at center of galaxies. After a star by SMBH, highly elliptical orbit debris stream will be gradually circularized due to self-crossing, and then form an accretion disk. The recent TDE candidate AT 2019avd has double peaks in its optical light curve, X-ray emerges near second peak. durations are ~400 600 days, respectively, separation between them is ~700 days. We fit spectral energy distribution (SED)...
We constrain the distance of gamma-ray burst (GRB) prompt emission site from explosion centre R, by determining location electron's self-absorption frequency in GRB optical-to-X/γ-ray spectral energy distribution, assuming that optical and γ-ray emissions are among same synchrotron radiation continuum a group hot electrons. All possible regimes considered our analysis. The method has only two assumed parameters, namely bulk Lorentz factor emitting source Γ magnetic field strength B region...
GRB 090417B was an unusually long burst with a T_90 duration of at least 2130 s and multi-peaked light curve energies 15-150 keV. It optically dark has been associated bright star-forming galaxy redshift 0.345 that is broadly similar to the Milky Way. This one few cases where host clearly identified for gamma-ray thus ideal candidate studying origin bursts. We find nature cannot be explained by high redshift, incomplete observations, or unusual physics in production afterglow. Assuming...
Abstract ASASSN-14ko was identified as an abnormal periodic nuclear transient with a potential decreasing period. Its outbursts in the optical and UV bands have displayed consistent smooth “fast rise slow decay” pattern since its discovery, which has recently experienced unexpected alteration last two epochs, revealed by our proposed high-cadence Swift observations. The new light curve profiles show bump during rising stages rebrightening declining stages, making them much broader...
The gamma-ray burst (GRB) prompt emission is believed to be from highly relativistic electrons accelerated in shocks. From the GRB high-energy power-law spectral indices β observed by Burst and Transient Source Experiment (BATSE) Large Area Detectors (LAD), we determine index, p, of electrons' energy distribution. Both theoretical calculations numerical simulations particle acceleration shocks show that p has a universal value ≈2.2–2.3. We distribution during GRBs not consistent with...
We present a comprehensive analysis of bright, long duration (T90 ~ 257 s) GRB 110205A at redshift z= 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb and BOOTES telescopes when the still radiating in gamma-ray band. Nearly 200 s observations were obtained simultaneously from optical, X-ray to gamma-ray, which makes it one exceptional cases study broadband spectral energy distribution across 6 orders magnitude during phase. By fitting time resolved spectra, we clearly...
Abstract Two X-ray sources were recently discovered by Irwin et al. that are compact companions to elliptical galaxies showing ultraluminous flares with fast rise (∼minute) and decay (∼hour), a peak luminosity ∼10 40–41 erg s −1 . Together two other found earlier, they constitute new type of transients cannot be attributed neutron stars, but might due intermediate-mass black holes (IMBHs; ). The flaring behavior is recurrent for at least sources. If the flare represents short period...
We propose to develop a wide-field and ultra-high-precision photometric survey mission, temporarily named "Earth 2.0 (ET)". This mission is designed measure, for the first time, occurrence rate orbital distributions of Earth-sized planets. ET consists seven 30cm telescopes, be launched Earth-Sun's L2 point. Six these are transit telescopes with field view 500 square degrees. Staring in direction that encompasses original Kepler four continuous years, this monitoring will return tens...
AT 2019avd is a nuclear transient detected from infrared to soft X-rays, though its nature yet unclear. The source has shown two consecutive flaring episodes in the optical and bands second flare was covered by X-ray monitoring programs. During this flare, UVOT/Swift photometries revealed plateaus: one observed after peak other appeared ~240 days later. Meanwhile, our NICER XRT/Swift campaigns show declines emission, during first plateau 70-90 optical/UV decline. evidence suggests that could...
GRB 120422A is a low-luminosity Gamma-ray burst (GRB) associated with bright supernova, which distinguishes itself by its relatively short T90 ~ 5 s and an energetic X-ray tail. We analyze the Swift BAT XRT data discuss physical implications. show that early steep decline in light curve can be interpreted as curvature tail of late emission episode around 58-86 s, curved instantaneous spectrum at end episode. Together main activity first 20 weak from 40 to 60 prompt variable, points towards...
The nature of ultra-luminous X-ray sources (ULXs) has long been plagued by an ambiguity about whether the central compact objects are intermediate-mass (IMBH, >~ 10^3 M_sun) or stellar-mass (a few tens black holes (BHs). high luminosity (~ 10^39 erg/s) and super-soft spectrum (T ~ 0.1 keV) during state ULX source X-1 in galaxy M101 suggest a large emission radius (>~ 10^9 cm), consistent with being IMBH accreting at sub-Eddington rate. However, recent kinematic measurement binary orbit this...
Abstract Tidal disruption events (TDEs) can uncover the quiescent black holes (BHs) at center of galaxies and also offer a promising method to study them. In partial TDE (PTDE), BH’s tidal force cannot fully disrupt star, so stellar core survives only varied portion mass is bound BH feeds it. We calculate event rate PTDEs full TDEs (FTDEs). general, higher than that FTDEs, especially for larger BHs, detection approximately dozens per year, as observed by Zwicky Transient Factory. During...
Abstract Recently, two fast X-ray transients (XT1 and XT2) have been reported from the search in Chandra Deep Field (CDF) data. Each transient shows an initial plateau lasting around hundreds to thousands of seconds followed by a rapid decay light curve. In particular, CDF-S XT2 is found be associated with galaxy at redshift z = 0.738 was explained as counterpart binary neutron-star merger event. this Letter, motivated short duration slopes transients, we consider alternative interpretation...