Z. J. Jiang

Yunnan University

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Li-Sheng Geng

Beihang University

D. Kuleshov

Institute for Nuclear Research

W. Zeng

Yunnan University

Z. G. Yao

Chinese Academy of Sciences

Y. H. Yao

Institute of High Energy Physics

X. N. Sun

Guangxi University

D. L. Xu

Shanghai Jiao Tong University

H. K. Lv

Chinese Academy of Sciences

F. Shi

Chinese Academy of Sciences

M. M. Ge

Yunnan University

Cooperative Institutions

Chinese Academy of Sciences

909

Institute of High Energy Physics

624

University of Chinese Academy of Sciences

384

University of Science and Technology of China

272

Southwest Jiaotong University

231

Campbell Collaboration

193

Gansu Great Wall Electrical and Electronics Engineering Research Institute

173

Purple Mountain Observatory

154

Shandong University

139

Nanjing University

130

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Likely Detection of GeV Gamma-Ray Emission from the Composite Supernova Remnant COMP G327.1+1.1 with Fermi-LAT

The Astrophysical Journal (2021)

Yunchuan Xiang Yi Xing Z. J. Jiang

Abstract We report the likely GeV γ -ray emission from the composite supernova remnant (SNR) COMP G327.1+1.1 by analyzing ∼12.2 yr of the Fermi Large Area Telescope (Fermi-LAT) Pass 8 data. We found the features of its spectrum and luminosity are well consistent with those of the observed COMP SNRs in the Milky Way. Moreover, the position of the source matches those in radio and TeV energy bands; we propose that the γ -ray source is likely to be a GeV counterpart of COMP G327.1+1.1. Considering the case of the association from COMP G327.1+1.1 and the γ -ray source, we interpreted its broadband spectral energy distribution (SED) by using three simple stationary models including one-zone and two-zone leptonic models and a one-zone leptohadronic model. We found that the simple two-zone model dominated by leptons can better explain its SED. More high-energy data are expected to firmly confirm the association between the γ -ray source and COMP G327.1+1.1 in the future.

Spectral energy distribution

10.3847/1538-4357/abe624

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Measurements of All-Particle Energy Spectrum and Mean Logarithmic Mass of Cosmic Rays from 0.3 to 30 PeV with LHAASO-KM2A

Physical Review Letters (2024)

Z. Cao F. Aharonian Axikegu Y. X. Bai Y. W. Bao

We present the measurements of all-particle energy spectrum and mean logarithmic mass of cosmic rays in the energy range of 0.3-30 PeV using data collected from LHAASO-KM2A between September 2021 and December 2022, which is based on a nearly composition-independent energy reconstruction method, achieving unprecedented accuracy. Our analysis reveals the position of the knee at 3.67±0.05±0.15 PeV. Below the knee, the spectral index is found to be -2.7413±0.0004±0.0050, while above the knee, it is -3.128±0.005±0.027, with the sharpness of the transition measured with a statistical error of 2%. The mean logarithmic mass of cosmic rays is almost heavier than helium in the whole measured energy range. It decreases from 1.7 at 0.3 PeV to 1.3 at 3 PeV, representing a 24% decline following a power law with an index of -0.1200±0.0003±0.0341. This is equivalent to an increase in abundance of light components. Above the knee, the mean logarithmic mass exhibits a power law trend towards heavier components, which is reversal to the behavior observed in the all-particle energy spectrum. Additionally, the knee position and the change in power-law index are approximately the same. These findings suggest that the knee observed in the all-particle spectrum corresponds to the knee of the light component, rather than the medium-heavy components.

Spectral index

Logarithmic mean

Particle (ecology)

10.1103/physrevlett.132.131002

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Citations (12)

Spectral hardening of cosmic ray protons and helium nuclei in supernova remnant shocks *

Chinese Physics C (2019)

Wen-Hui Lin Biwen Bao Z. J. Jiang Li Zhang

Abstract The observed hardening of the spectra of cosmic ray protons and helium nuclei is studied within the model of nonlinear diffusive shock acceleration of supernova remnants (SNRs). In this model, the injected particles with energies below the spectral " knee” are assumed to be described by two populations with different spectral indexes around 200 GeV. The high-energy population is dominated by the particles with energies above 200 GeV released upstream of the shock of SNR, and the low-energy population is attributed to the particles with energies below 200 GeV released downstream of the shock of SNR. In this scenario, the spectral hardening of cosmic ray protons and helium nuclei observed by PAMELA, AMS-02, and CREAM experiments can be reproduced.

Hardening (computing)

10.1088/1674-1137/43/5/053103

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Citations (3)

Fermi-LAT Detection of GeV γ-Ray Emission from the Type Ia Supernova Remnant G272.2–3.2

The Astrophysical Journal (2021)

Yunchuan Xiang Z. J. Jiang

A new γ-ray source with a significance level of approximately 5σ was reported in the region of the supernova remnant (SNR) G272.2–3.2 by analyzing the approximately 12.4 yr of observation data from the Fermi Large Area Telescope. Its γ-ray spatial distribution did not show an extended feature, and it had a soft spectrum with a spectral index of 2.56 ± 0.01 in the power-law model. No significant variability of its light curve with 10 time bins was identified, and its spatial positions in the X-ray and GeV bands overlapped. We suggest that the new γ-ray source is a likely counterpart of SNR G272.2–3.2. Analyzing its spectrum, we discussed the likely origins of the γ-ray emission.

Spectral index

10.3847/1538-4357/ac0fe4

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Citations (3)

Evolution of optical spectral index and variability properties of S5 0716+714

Research in Astronomy and Astrophysics (2010)

Jianming Hao Baijuan Wang Z. J. Jiang B. Z. Dai

We analyze the spectral variability and spectral evolution in the optical energy region by using multiband (BVRI) optical observations of S5 0716+714 spanning 1994 to 2005. The spectrum hardens when the source becomes brighter, which is consistent with general BL Lac objects. The spectral evolution parameter implies that the spectral variability is small in optical bands over 10 years. A simple model representing the variability of a synchrotron component can explain the spectral changes. In addition, we employ the z-transformed discrete correlation function (ZDCF) to analyze the optical multiband flux correlation. The long-term light curve behavior reveals that the variability time scales are 3.5 yr in the B-band, 3.3 yr in the V-band, 3.4 yr in the R-band and 3.5 yr in the I-band. The time lags between any two optical bands were not found when considering statistical errors.

Spectral index

Spectral slope

10.1088/1674-4527/10/2/003

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Citations (7)

Deep view of composite SNR CTA1 with LHAASO in γ-rays up to 300 TeV

Science China Physics Mechanics and Astronomy (2025)

Zhen Cao F. Aharonian Axikegu Y. X. Bai Y. W. Bao

10.1007/s11433-024-2479-4

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Study on Variability and Spectral Properties of Blazar 3C 273 with Long-term Multi-band Optical Monitoring from 2006 to 2015

Publications of the Astronomical Society of the Pacific (2018)

W. Zeng Qing-Jiang Zhao B. Z. Dai Z. J. Jiang Xiongfei Geng

We present long-term optical multi-band photometric monitoring of blazar 3C 273, from 2006 May 19 to 2015 March 31 with high temporal resolution in the BVRI bands. The source is in a steady state and showed very small variability, with the values of the fractional variability amplitude of , , and in B, V, R and I, respectively. The intra-night point-to-point fractional variability (Fpp) in each band is below 1.0%, and the Fpp variation amplitude increase from the B-band to the I-band. We find a variability with the timescale of 5.8 ± 2.9 minutes in the I-band on 2009 March 11. This fast variability requires the comoving magnetic field strength in the jet above 18 G with a Doppler factor . Using the discrete correlation function (DCF), the B- and I-band light curves are examined for correlation on whole campaign. Low significance (∼99.73 percent confidence) correlations with the I-band lags the B-band variations are observed. The spectral behaviors in the different variability episodes are studied. "Bluer-when-brighter" spectral behavior is presented for the whole campaign, while there is an opposite tendency when . The weak of the correlation between B- and I-band and the spectrum analysis indicate that the optical radiation consists of two variable components.

Spectral slope

Broad band

10.1088/1538-3873/aa9dfe

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Citations (8)

Exploring γ-Ray Flares in the Long-term Light Curves of CTA 102 at GeV Energies

The Astrophysical Journal Supplement Series (2022)

Xiongfei Geng Nan Ding Gang Cao Liu Yang Biwen Bao

Abstract Blazar CTA 102 experienced an intense multiwavelength activity phase from 2015 to 2018; in particular, an unprecedented outburst was observed from 2016 October to 2017 February. In this work, we extract a 7 day binned γ -ray light curve from 2008 August to 2018 March in the energy range 0.1–300 GeV and identify three main outbursts. We study in detail the short-timescale variability of these three outbursts via an exponential function with parameterized rise and decay timescales. The obtained shortest rise and decay timescales are 0.70 ± 0.05 hr and 0.79 ± 0.27 hr, respectively. Based on these variability timescales, the physical parameters of the flaring region (e.g., the minimum Doppler factor and the emission region size) are constrained. The short-timescale flares exhibit a symmetric temporal profile within the error bars, implying that the rise and decay timescales are dominated by the light-crossing timescale or by disturbances caused by dense plasma blobs passing through the standing shock front in the jet region. We also find that the best-fitting form of the γ -ray spectra during the flare period is a power law with an exponential cutoff. The derived jet parameters from the spectral behavior and the temporal characteristics of the individual flares suggest that the γ -ray emission region is located upstream of the radio core. The extreme γ -ray flare of CTA 102 is likely to have been caused by magnetic reconnection.

Flare

Exponential decay

Solar flare

10.3847/1538-4365/ac64f6

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Citations (3)

Multi-objective Scheduling Optimization of Microgrids with Vehicle-to-Grid (V2G) Participation

Haolin Li Xilong Zhang P. Ma Z. J. Jiang Dongpeng Li

Vehicle-to-Grid

10.1109/epee63731.2024.10875120

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