Modifying general relativity (GR) with a scalar field is a promising attempt to address issues of dark matter and dark energy in astrophysics and cosmology. It can also generate solutions different from those in GR for compact stars. We study the solutions for neutron stars when gravity is modified by a scalar field coupled with the Gauss-Bonnet invariant, causing the remarkable phenomenon of...
In this work, a time-dependent modeling is developed to study the emission properties of blazars in the low state. Motivated by various observations, we speculate and assume that numerous discrete radiation zones throughout the jet of a blazar contribute to the broadband emission. We model the temporal evolution of the electron spectrum in each emission zone taking into account the injection,...
Continuous gravitational wave searches with terrestrial, long-baseline interferometers are hampered by long-lived, narrowband features in the power spectral density of the detector noise, known as lines. Candidate GW signals which overlap spectrally with known lines are typically vetoed. Here we demonstrate a line subtraction method based on adaptive noise cancellation, using a recursive least...
It is difficult to identify hadronic PeVatrons (the PeV particle accelerator) from the ultra-high-energy (UHE, $E$ > 100 TeV) gamma-ray sources, which is however crucial in revealing the origin of cosmic rays. As an endeavor in this regard, we focus in this work on the UHE gamma-ray source 1LHAASO J1857+0203u, which may be associated with supernova remnant (SNR) G35.6−0.4 and H II region...
Tidal disruption events (TDEs) provide a valuable probe in studying the dynamics of stars in the nuclear environments of galaxies. Recent observations show that TDEs are strongly overrepresented in post-starburst or "green valley" galaxies, although the underlying physical mechanism remains unclear. Considering the possible interaction between stars and active galactic nucleus (AGN) disk, the...
We report on long-term evolution of gamma-ray flux and spin-down rate of the two bright gamma-ray pulsars,PSR J2021+4026 and Vela (PSR B0833-45). PSR J2021+4026 shows repeated state changes in gamma-ray flux and spin-down rate. We report two new state changes, one from a low gamma-ray flux to a high flux that occurred around MJD 58910 and another one from high to low flux that occurred around...
Propagating individual cosmic rays in synthetic three-dimensional Kolmogorov turbulence, we calculate their anisotropy at the location of an observer. These are the first calculations of the cosmic ray anisotropy down to TeV energies for values of the turbulence coherence length that are realistic for the interstellar medium. We calculate the power spectrum 𝐶𝑙, of the cosmic ray anisotropy for...
Chromatic break and/or plateau observed in the early optical and X-ray afterglow light curves challenge the conventional external shock models of gamma-ray bursts (GRBs). Detection of TeV gamma-ray afterglows indicates strong gamma-ray production within the afterglow jets.
We investigate the cascade radiations of the $e^\pm$ production via the $\gamma\gamma$ interaction in the jets. Our...
Binary black holes (BBHs) are among the most important sources of gravitational waves (GWs). Recent studies suggest that BBHs may form and merge in the vicinity of supermassive black holes (SMBHs), leading to overestimated black hole masses due to gravitational and Doppler redshift. A distinctive characteristic of these GW sources is their acceleration around the SMBH, allowing for their...
Ultra-compact white dwarf binaries are strong sources of gravitational radiation, and the galactic white dwarf binaries are major sources for the space-based laser interferometer gravitational wave observatory LISA. Some of these binary systems will also be visible through electromagnetic observations, making them multi-messenger astronomy sources. By comparing the phase differences between...
GRB 221009A is an exceptionally bright and relatively nearby event, displaying a substantial abundance of very high energy (VHE) photons as observed by the two LHAASO instruments: WCDA and KM2A. The prevailing model attributes the origin of these VHE photons to synchrotron self-Compton (SSC) radiation arising from external shocks within the afterglow of the burst. Nevertheless, when gamma...
The origin of the knee in the cosmic ray (CR) spectrum is still unknown after 65 years of studies. Here, within the framework of anisotropic CR diffusion models, we show that the knee is a time-dependent feature, and that the flux in this region contains major contributions from one or a few nearby recent CR sources. We calculate the propagation of CRs in the Jansson-Farrar galactic magnetic...
While the GeV $\gamma$-rays emission of starburst galaxies (SBG) is commonly thought to arise from hadronic interactions between accelerated cosmic rays and interstellar gas, the origin of the TeV $\gamma$-ray emission is more uncertain. One possibility is that a population of pulsar wind nebulae (PWNe) in these galaxies could be responsible for the TeV $\gamma$-ray emission. In this work,...
Data gaps in space-borne gravitational wave detectors, arising from factors such as micrometeorite collisions or hardware malfunctions, pose a significant challenge in gravitational wave data processing. The milli-Hertz observation frequency range and possible day-scale occurance rate for the gap makes the appropriate estimating of the noise property, and correspondingly the following data...
Future space-based laser interferometric detectors will be able to observe gravitational waves (GWs) generated during the inspiral phase of stellar-mass binary black holes (SmBBHs), which contain a wealth of important physical information concerning astrophysical formation channels and fundamental physics constraints. However, the detection and characterization of GWs from these SmBBHs remains...
Gravitational wave (GW) searches using a pulsar timing array (PTA) are typically limited to the GW frequency $\le 4 \times 10^{-7}$ Hz, due to the average observational cadence of 2 weeks for a single pulsar. By taking advantage of asynchronous observations of multiple pulsars, PTA has the potential to detect GW signals with frequencies higher than the Nyquist frequency of a single pulsar. An...
The Southern Wide-field Gamma-ray Observatory (SWGO) is a proposed next-generation gamma-ray survey experiment that will cover the southern sky with high sensitivity and a wide field of view. It will be built in South America to complement HAWC and LHAASO in the Northern Hemisphere. We designed a lake array proposal for SWGO to record particles from extensive air showers initiated by high...
Relativistic outflows or jets with more than 99% of the light speed emerge in pulsar wind nebulae, gamma-ray bursts, and active galactic nuclei. Such relativistic jets are thought to be launched through magnetic processes, which implies magnetically dominated outflows. However, a multi-wavelength spectrum suggests that jets must be kinetically dominated at the gamma-ray emission region. This...
We develop a framework to compute the tidal response of a Kerr-like compact object in terms of its reflectivity, compactness, and spin, both in the static and the frequency-dependent case. Here we focus on the low-frequency regime, which can be solved fully analytically. We highlight some remarkable novel features, in particular: i) Even in the zero-frequency limit, the tidal Love numbers...
We investigate the detectability of GWs that have been lensed by a spinless stellar-mass BH. By numerically solving the full relativistic linear wave equation in the spacetime of a Schwarzschild BH, we find that the strong gravity can create unique signals in the lensed waveform, particularly during the merger and ringdown stages. The differences in terms of fitting factor between the lensed...
The Jiangmen Underground Neutrino Observatory (JUNO) will be a 20kton liquid scintillator detector, currently under construction in southern China. JUNO will be instrumented with close to 18,000 20-inch photomultiplier tubes (PMTs), possessing the highest photocathode coverage of any kiloton-scale liquid scintillator or Cherenkov detector to date. With its first-rate size, PMT coverage and...
Fast radio bursts (FRBs) are the brightest radio transients in the universe. Since their unexpected discovery in the 21st century, their extreme nature has become one of the biggest mysteries in astrophysics. FRBs also serve as unique probes of the universe, opening up a new field of FRB cosmology. In 2020, Galactic FRBs were detected originating from magnetar bursts, pinning down one of the...
The origin of the recently discovered new class of transients, X-ray quasi-periodic eruptions (QPEs), remains a puzzle. Due to their periodicity and association with tidal disruption events and active galactic nuclei (AGN), it is natural to relate these eruptions to stars or compact objects in tight orbits around supermassive black holes. In our work, we predict the properties of emission from...
The forbidden dark matter cannot annihilate into heavier partner or SM particles by definition at the late stage of the cosmological evolution. We point out the possibility of reactivating the annihilation channel of forbidden dark matter around supermassive black holes. The subsequent decay of the annihilation products to photon leaves unique signal around the black hole, which can serve as...
Neutron star − black hole (NSBH) merger events bring us new opportunities to constrain theories of stellar and binary evolution, and understand the nature of compact objects. In this work, we investigate the formation of merging NSBH binaries at solar metallicity by performing a binary population synthesis study of merging NSBH binaries with the newly developed binary population synthesis code...
In this talk, I will introduce a simple toy model that can simultaneously explain magnetar glitches and anti-glitches. It is based on the idea of mass ejection from the magnetar and how, as a result of the ejecta being trapped by the magnetic field, a time-varying mass quadrupole moment is established leading ultimately to gravitational wave emission. I will use astrophysical arguments to...
We will present results on fully non-linear numerical evolutions of the Einstein-(multi)--Klein-Gordon equations to describe head-on collisions of ℓ-boson stars. Despite being spherically symmetric, ℓ-boson stars have a (hidden) frame of reference, used in defining their individual multipolar fields. To assess the impact of their relative orientation, we perform simulations with different...
Space-based gravitational wave detectors like TianQin or LISA could observe extreme-mass-ratio-inspirals (EMRIs) at millihertz frequencies. The accurate identification of these EMRI signals from the data plays a crucial role in enabling in-depth study of astronomy and physics. We aim at the identification stage of the data analysis, with the aim to extract key features of the signal from the...
Xin & Haiman (2021) predicted that the Vera C Rubin Observatory’s Legacy Survey of Space and Time (LSST) will observe up to 100 million quasars. Among these up to approximately 100 ultra-compact massive black hole binaries binaries can be identified, which 5-15 years later can then be detected in gravitational waves (GWs) by the future Laser Interferometer Space Antenna (LISA). In this talk, I...
We present our new model for the description of the $\rm{PeV}-\rm{TeV}$ Galactic gamma-ray emission assuming discrete distributions of cosmic-ray sources. Based on this model, we investigate the impact of the discreteness of the locations of the cosmis-ray sources and of the diffusion mechanism responsible for the propagation of cosmic rays on the morphology of the VHE Galactic diffuse...
We propose a novel mechanism for constraining warm dark matter (WDM) models via the so-called “memory of reionization” effect, which is that the thermal history of gas after cosmic reionization is sensitive to when the gas is reionized. The suppression of small-scale structure due to WDM affects the evolution of post-reionization gas, while thermal relics can couple to ionized bubbles at the...
TeV gamma-ray halos are a new subclass of gamma-ray sources that could explain the positron excess measured by PAMELA, Fermi-LAT, and AMS-02. Geminga and Monogem are the first two gamma-ray halo candidates reported by the HAWC collaboration. The diffusion coefficient derived by the HAWC Collaboration, (4.5 +/- 1.2)x10^27 cm^2/s, differs more than 100 times from the average galactic value. We...
SNR G150.3+4.5 was first identified in radio and has a hard overall GeV spectrum with $\sim 1.5^\circ$ radius. Radio observations have revealed a bright hard arc with an index of $\sim -0.40$ in contrast to the index of $\sim -0.69$ for the other part. This arc is coincident with the soft Fermi source 4FGL J0426.5+5434 (Hereafter SrcX) and the soft ultra-high-energy (UHE) source 1LHAASO...
Though decades of studies of coherent pulsar radiation, the physical mechanism of the radio emission at kinetic micro-scales is still under investigation. One of the proposed mechanisms is the linear acceleration emission that is coherent antenna-type of radiation. The mechanism is based on plasma particles oscillating along magnetic field lines and producing linear acceleration...
In recent years, there have been limits placed on neutrino-dark matter scattering using the neutrino echo effect and using boosted dark matter detection respectively. In this work, we aim to combine the analysis on both parts by using galactic supernovae neutrino fluxes covering an extended energy range, which shows effects from both phenomena, thereby matching the parameter spaces from the...
Space-borne gravitational wave detectors can detect sources like the merger of massive black holes. The rapid identification and localization of the source would play a crucial role in multi-messenger observation. The geocentric orbit of the space-borne gravitational wave detector, TianQin, makes it possible to conduct real-time data transmission. In this manuscript, we develop a search and...
In light of large-scale anomalies in observations and tensions in important cosmological parameters like $H_0$ and $S_8$ of our Universe, we formulated possible dark energy inhomogeneities as the cosmological perturbations on superhorizon scales, sourced by some light scalar field. Based on this model, we discuss the possible impacts of the dark energy inhomogeneities on the anisotropic...
In this report, the authors present their Bayesian parameter estimation progress in inferring the properties of stellar mass binary black holes using the TianQin and LISA missions, alone and in combination. Two representative stellar-mass black hole binary (BBH) systems, GW150914 and GW190521, are chosen as fiducial sources. The work focuses on establishing the ability of TianQin to infer the...
For illustration of the cosmic accelerated expansion of the universe, we will consider the modified Friedmann equations of some torsion-based theory of gravity. In this way, the cosmological parameters such as equation of state, phase-plane, squared speed of sound etc are being developed and examined graphically. For more insights of parameters, power-law forms of scale factor and...
PSR J1906+0746 is a young binary pulsar with a spin period of P ∼ 144 ms in a very short 4-hr orbit around another neutron star. It provides a great opportunity to study both the relativistic spin-precession predicted by General Relativity (GR), and the little-understood radio pulsar emission in a single source in a self-consistent way. Discovered with Arecibo in 2004, it showed both a “main...
Compact binary millisecond pulsars are systems in which the pulsar’s relativistic wind can strongly irradiate and ablate their companion star. Also known as spiders, they represent a promising site to find super-massive neutron stars. In this presentation I will show our multi-band optical light curves of PSR J1622-0315, one of the most compact known redbacks. The light curves indicate that...
TeV halos have drawn extensive attention since the first discovery from the HAWC observatory. These huge gamma-ray structures around pulsars provide important information about the particle acceleration and propagation in pulsar-powered systems, and probe the characteristics of the ambient interstellar environments. With HAWC, LHAASO, and other ground-based and space-borne gamma-ray...
The origin of ultra-high-energy cosmic rays (UHECRs; >10 EeV) is unknown. Gamma-rays and neutrinos produced in CR-induced hadronic interactions can serve as the smoking gun pointing back to sources. Motivated by the fact that IceCube-measured diffuse TeV neutrino flux is comparable to Waxman-Bahcall bound derived from the detected UHECR flux, we assume a common origin of UHECRs and TeV...
The millihertz gravitational wave band is expected to be opened by space-borne detectors like TianQin. Various mechanisms can produce short outbursts of gravitational waves, whose actual waveform can be hard to model. In order to identify such gravitational wave bursts and not to misclassify them as noise transients, we proposed a proof-of-principle energy excess method, that utilized the...
Estimating the spin of SgrA∗ is one of the current challenges we face in understanding the center of our Galaxy. In the present work, we show that detecting the gravitational waves (GWs) emitted by a brown dwarf inspiraling around SgrA∗ will allow us to measure the mass and the spin of SgrA∗ with unprecedented accuracy. Such systems are known as extremely large mass-ratio inspirals (XMRIs) and...
TRopIcal DEep-sea Neutrino Telescope (TRIDENT) is a next-generation neutrino observatory to be located in the South China Sea. With its large instrumented volume, unique position near the equator and use of advanced hybrid digital optical modules (hDOMs), TRIDENT aims to discover multiple astrophysical neutrino sources and probe all-flavor neutrino physics. In contrast to track-like events,...
Starburst Galaxies (SBs) have higher star formation rate and supernova (SN) explosion rate. Therefore, SBs are promising cosmic-rays (CRs) accelerator. Such CRs produced in the birth and death of stars are expected to produce gamma-ray emission. The identification of supernova remnant and the observation of galactic-scale outflow indicate that SN-triggered activities play an important role in...
The gravitational waves from the binary neutron star merger GW170817 were accompanied by a multi-wavelength electromagnetic counterpart, which confirms the association of the merger with a short gamma-ray burst (sGRB). The afterglow observations implied that the event was accompanied by a narrow, ~5°, and powerful, ~1050 erg, jet. We study the propagation of a Poynting flux-dominated jet...
The development of high-energy data integration analysis tool (HEtools) is the preparation for the next-generation space high-energy detection facility, such as SVOM, VLAST, etc. We will present some of our work using existing Gamma-Ray Burst (GRB) data and this tool.
Recently, we developed a model of outflow-cloud interactions to explain the association between TDE and high-energy neutrinos, which is used between AT2019dsg and IC191001A (Wu et al. 2022). Furthermore, based on this model, we developed a neutrino background model to discussed the contribution from TDE.
Using cosmological hydrodynamic zoom-in simulations and semi-analytical models, we explore the role of stellar-mass primordial black holes (PBHs) on first star formation, and their imprint on the cosmic radiation background during the epoch of reionization ($z\geq 6$), combining two competing effects: initial (isocurvature) perturbations induced by PBHs and BH accretion feedback. When PBHs...
The extraordinary GRB 221009A has an extremely luminous TeV emission. We analyzed the light curves both in TeV band and in MeV band. We found several special properties and try to figure them out. 1. Try to find the indication on the Lorentz factor based on the opacity of the TeV photons absorbed by the prompt MeV photons. 2. Try to figure out the early dip at 1-5 s of the TeV light curve. 3....
We present a new magnetohydrodynamic-particle-in-cell (MHD-PIC) code integrated into the \texttt{Athena++} framework.
It treats energetic particles as in conventional PIC codes while the rest of thermal plasmas are treated as background fluid described by MHD, thus primarily targeting at multi-scale astrophysical problems involving the kinetic physics of the cosmic-rays (CRs).
The code is...
The data of the last 60 years on the programs of long-term multi-frequency monitoring of active galactic nuclei 3C 273 are analyzed. A model is proposed for finding the parameters of close binary systems from supermassive black holes.
It has been established that 3C 273 can be a very massive binary system at the stage of evolution close to merging. Based on the obtained parameters, the...
The Brightest of all time (BOAT) GRB 221009A hasn’t been fully explained in multi-wavelength, especially including the TeV afterglows observed by LHAASO. The TeV afterglow has been interpreted as arising from a narrow jet, which could indicate the core of a structured jet. We here study a two-component jet model, including an inner narrow core and an outer wide wing with an angular structure,...
Astrophysical jets are relativistic outflows related to compact objects that spin and accretion. Accretor with different mass and size such as AGNs, GRBs, TDEs and microquasars involve different scales of jets. We unified multi-scale astrophysical jets by considering viewing angle and magnetic filed. Particle acceleration and variability are explained under this scheme.
The arrival directions of TeV cosmic rays on the sky display an anisotropy at the 0.1 percent level. This anisotropy contains a dipole and higher order multipoles. Small-scale anisotropies should contain important information about the properties of the turbulent magnetic fields in the interstellar medium. These anisotropies have been predicted to vary on a time-scale of a decade at TeV...
Large-scale $N$-body simulations have successfully reconstructed cosmic structure formation with increasing resolution and complexity, as observations corroborate. Complementary efforts have arrived at a hydrodynamical theory that explains cosmic structure evolution up to the non-linear regime. While the statistical properties of mass density perturbations for the observable universe as a...
