A5059460341- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Particle physics theoretical and experimental studies
- Pulsars and Gravitational Waves Research
- Solar and Space Plasma Dynamics
- Particle Detector Development and Performance
- Nonlinear Dynamics and Pattern Formation
- Chaos control and synchronization
- Optical Coherence Tomography Applications
- Complex Network Analysis Techniques
- Random lasers and scattering media
- Photocathodes and Microchannel Plates
- Optical Polarization and Ellipsometry
- Advanced Fiber Laser Technologies
- High-Energy Particle Collisions Research
- Opinion Dynamics and Social Influence
- Laser-Plasma Interactions and Diagnostics
- Ocular and Laser Science Research
- Advanced Computational Techniques and Applications
- Quantum chaos and dynamical systems
- Social Capital and Networks
Zhejiang University of Technology
2023
University of Potsdam
2013-2017
Deutsches Elektronen-Synchrotron DESY
2016
Rice University
2010-2012
Xiamen University of Technology
2012
Lanzhou University of Technology
2010
We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations instruments, providing data from radio to very-high-energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity 3-79 keV range, revealing that spectrum softens when source is dimmer until X-ray spectral shape saturates into a steep power law with photon index...
Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints diffuse radiation fields that fill universe. The detection significant emission above 100 GeV a distant quasar would show some radiated gamma-rays escape pair-production interactions with low-energy photons, be it extragalactic background light (EBL), or near supermassive black hole lying at jet's base. VERITAS detected up to ∼200 PKS 1441+25 (z = 0.939) during 2015 April,...
The polarization signatures of the blazar emissions are known to be highly variable. In addition small fluctuations angle around a mean value, sometimes large (> 180^o) swings observed. We suggest that such p henomena can interpreted as arising from light-travel-time effects within an underlying axisymmetric emission region. present first simultaneous fitting multi-wavelength spectrum, variability and time-dependent features correlated optical gamma-ray flaring event prominent 3C279,...
We present a detailed analysis of time- and energy-dependent synchrotron polarization signatures in shock-in-jet model for gamma-ray blazars. Our calculations employ full 3D radiation transfer code, assuming helical magnetic field throughout the jet. The code considers emission from an ordered field, takes into account all light-travel-time other relevant geometric effects, while self-Compton external Compton effects are taken care with 2D MCFP code. consider several possible mechanisms...
The high-frequency-peaked BL Lacertae object 1ES 0229+200 is a relatively distant (z = 0.1396), hard-spectrum (Gamma ~ 2.5), very-high-energy-emitting (E > 100 GeV) gamma-ray blazar. Very-high-energy measurements of this active galactic nucleus have been used to place constraints on the intensity extragalactic background light and intergalactic magnetic field. A multi-wavelength study centered around very-high-energy observations by VERITAS presented. This obtained, over period three years,...
(abridged) We present a new time-dependent multi-zone radiative transfer code and its application to study the SSC emission of Mrk 421. The couples Fokker-Planck Monte Carlo methods, in 2D geometry. For first time all light travel effects (LCTE) are fully considered, along with proper treatment Compton cooling, which depends on them. set simple scenarios where variability is produced by injection relativistic electrons as `shock front' crosses region. consider from two components, second one...
TeV J2032+4130 was the first unidentified source discovered at very high energies (VHE; E $>$ 100 GeV), with no obvious counterpart in any other wavelength. It is also extended to be observed VHE gamma rays. Following its discovery, intensive observational campaigns have been carried out all wavelengths order understand nature of object, which met limited success. We report here on a deep observation J2032+4130, based 48.2 hours data taken from 2009 2012 by VERITAS (Very Energetic Radiation...
We present very high energy (VHE) imaging of MGRO J2019+37 obtained with the VERITAS observatory. The bright extended ($\sim2^{\circ}$) unidentified Milagro source is located towards rich star formation region Cygnus-X. resolved into two sources. faint point-like VER J2016+371 overlaps CTB 87, a filled-center remnant (SNR) no evidence supernova shell at time. Its spectrum well fit in $0.65 - 10$ TeV range by power-law model photon index $2.3\pm0.4$. J2019+368 ($\sim1^{\circ}$) source, that...
We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in gamma rays, PMN J0948+0022 ($z$ = 0.5846). A gamma-ray flare was observed by Large Area Telescope board Fermi January, reaching a daily peak flux 0.1-100 GeV energy range (155 $\pm$ 31) $\times$10$^{-8}$ ph cm$^{-2}$ s$^{-1}$ 2013 January 1, corresponding to an apparent isotropic luminosity about 1.5$\times$10$^{48}$ erg s$^{-1}$. The flaring period...
HESS J0632+057 is the only gamma-ray binary known so far whose position in sky allows observations with ground-based observatories both northern and southern hemispheres. Here we report on long-term of conducted Very Energetic Radiation Imaging Telescope Array System High Energy Stereoscopic Cherenkov telescopes X-ray satellite Swift, spanning a time range from 2004 to 2012 covering most system's orbit. The very-high-energy (VHE) emission found be variable correlated that at energies. An...
We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope and UV Optical data between 2009 February 19 2013 June 8. This resides at a redshift $z\ge0.6035$, displaying significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production extragalactic background light. more than hours from three years, multiwavelength light curve spectral energy distributions. The source shows...
In 2013 March, a flaring episode from the Crab Nebula lasting ∼2 weeks was detected by Fermi-LAT (Large Area Telescope on board Fermi Gamma-ray Space Telescope). The Very Energetic Radiation Imaging Array System (VERITAS) provides simultaneous observations throughout this period. During flare, 20 fold increase in flux above average synchrotron >100 MeV seen Nebula. Simultaneous measurements with VERITAS are consistent non-variable long-term at TeV energies. Assuming linear correlation...
We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band by robotic telescopes Super-LOTIS and iTelescope, UV Swift UVOT, X-ray Telescope (XRT), high-energy gamma-ray with Fermi Large Area (LAT) very-high-energy (VHE) VERITAS above 315 GeV, all taken between 17 April 2012 1 June (MJD 56034 56079). The contemporaneous variability spectral energy distribution is explored in context a simple synchrotron self Compton (SSC) model. In SSC emission...
During moonlit nights, observations with ground-based Cherenkov telescopes at very high energies (VHEs, GeV) are constrained since the photomultiplier tubes (PMTs) in telescope camera extremely sensitive to background moonlight. Observations VERITAS standard configuration performed only a moon illumination less than 35% of full moon. Since 2012, collaboration has implemented new observing mode under bright moonlight, by either reducing voltage applied PMTs (reduced-high-voltage; RHV...
We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 560\,GeV, is well described by a power law with spectral index $4.33 \pm 0.09$. integral flux above $200\,$GeV for this period was $(1.69 0.06) \times 10^{-11} \, \mathrm{ph} \mathrm{cm}^{-2} \mathrm{s}^{-1}$, corresponding to 6.9\% Crab Nebula flux. also combined $\gamma$-ray spectrum Fermi Large Area Telescope covering an energy...
[abridged] We present results of modeling the SED and multiwavelength variability bright FSRQ PKS1510-089 with our time-dependent multizone Monte Carlo/Fokker-Planck code (Chen et al. 2001). As primary source seed photons for inverse Compton scattering, we consider radiation from broad line region (BLR), molecular torus, local synchrotron (SSC). Different scenarios are assessed by comparing simulated light curves SEDs one best flares PKS1510-089, in March 2009. The time-dependence its...
ABSTRACT The F-type star KIC 8462852 has recently been identified as an exceptional target for search extraterrestrial intelligence (SETI) observations. We describe analysis methodology optical SETI, which we have used to analyze nine hours of serendipitous archival observations made with the VERITAS gamma-ray observatory between 2009 and 2015. No evidence pulsed beacons, above a pulse intensity at Earth approximately , is found. also discuss potential use imaging atmospheric Cherenkov...
We report on deep observations of the extended TeV gamma-ray source MGRO J1908+06 made with VERITAS very high energy (VHE) observatory. Previously, emission has been attributed to pulsar wind nebula (PWN) Fermi-LAT PSR J1907+0602. detect at a significance level 14 standard deviations (14 sigma) and measure photon index 2.20 +/- 0.10_stat 0.20_sys. The is extended, covering region near J1907+0602 also extending towards SNR G40.5--0.5. When fitted 2-dimensional Gaussian, intrinsic extension...
The Galactic center is an interesting region for high-energy (0.1-100 GeV) and very-high-energy (E > 100 gamma-ray observations. Potential sources of GeV/TeV emission have been suggested, e.g., the accretion matter onto supermassive black hole, cosmic rays from a nearby supernova remnant (e.g. SgrA East), particle acceleration in plerion, or annihilation dark particles. has detected by EGRET Fermi/LAT MeV/GeV energy band. At TeV energies, was with moderate significance CANGAROO Whipple 10...
ABSTRACT The Galactic Center ridge has been observed extensively in the past by both GeV and TeV gamma-ray instruments revealing a wealth of structure, including diffuse component point sources G0.9+0.1 (a composite supernova remnant) Sgr A* (believed to be associated with supermassive black hole located at center our Galaxy). Previous very high energy (VHE) observations H.E.S.S. experiment have also detected an extended along plane >300 regime. Here we report on from 2010 2014 VERITAS...
ABSTRACT The TeV binary system LS I +61° 303 is known for its regular, non-thermal emission pattern that traces the orbital period of compact object in 26.5 day orbit around B0 Ve star companion. typically presents elevated apastron passage with flux levels between 5% and 15% steady from Crab Nebula (>300 GeV). In this article, VERITAS observations taken late 2014 are presented, during which bright flares at peaking above 30% were detected. This brightest such activity source ever seen...
We study the stochastic variation of blazar emission under a 2-D spatially resolved leptonic jet model we previously developed. Random events particle acceleration and injection in small zones within region are assumed to be responsible for flux variations. In addition producing spectral energy distributions that describe observed Mrk 421, further analyze timing properties simulated light curves, such as power density (PSD) at different bands, flux-flux correlations, well cross-correlation...
Blazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential observe blazars simultaneously at different wavelengths, especially in the X-ray and gamma-ray bands, where broadband spectral energy distributions usually peak. In this work, we report on three "target-of-opportunity" (ToO) observations Mrk 421, one brightest TeV blazars, triggered by strong flaring event energies 2014. These feature long, continuous,...
We present the results of 71.6 hours observations Geminga pulsar (PSR J0633+1746) with VERITAS very-high-energy gamma-ray telescope array. Data taken between November 2007 and February 2013 were phase-folded using a timing solution derived from data recorded by XMM-\emph{Newton} \emph{Fermi}-LAT space telescopes. No significant pulsed emission above 100 GeV is observed, we report upper limits at 95% confidence level on integral flux 135 (spectral analysis threshold) 4.0$\times10^{-13}$...