LHAASO J1908+0621 has been recently detected as a source emitting $γ$-rays with energies above 100 TeV, and the multiband observations show that a break around 1 TeV appears in the $γ$-ray spectrum. We have reanalyzed the GeV $γ$-ray properties for the 100 TeV source using 14 years of data recorded by the Fermi Large Area Telescope (Fermi-LAT). The spectrum in the energy range range 30-500 GeV has an index of 1.50 $\pm$ 0.26, which is much smaller than that detected in the TeV $γ$-rays. Additionally, the radiation properties of this source are investigated based on a one-zone time-dependent model. In the model, LHAASO J1908+0621 is associated with a pulsar wind nebula (PWN) powered by the pulsar PSR J1907$+$0602. High-energy particles composed of electrons and positrons are injected into the nebula. Multiband nonthermal emission is produced via synchrotron radiation and inverse Compton scattering (ICS). Taking the effect of radiative energy losses and adiabatic cooling into account, the spectral energy distribution from the model with a broken power-law for the distribution of the injected particles can explain the detected fluxes in the $γ$-ray bands. The results support that LHAASO J1908+0621 originates from the PWN powered by PSR J1907$+$0602, and the $γ$-rays with energy above 100 TeV are produced by the electrons/positrons in the nebula via ICS.
The Large High Altitude Air Shower Observatory (LHAASO) observed a dozen of gamma-ray sources with significant emission above 100 TeV, which may be strong candidates of PeVatrons. Neutrino observations are crucial to diagnose whether the gamma-ray radiative process is hadronic or leptonic. We use the Bayesian method to analyze the ten-year (2008-2018) IceCube data, and hence constrain the hadronic gamma-ray emission in the LHAASO sources. The present neutrino data show that the hadronic gamma-ray flux from Crab Nebula is lower than the observed gamma-ray flux at the 90% C.L. and contributes le…
Investigating Pulsar Wind Nebula DA 495: Insights from LHAASO and Multi-Wavelength Observations
State Key Laboratory of Particle Astrophysics & Experimental Physics Division & Computing Center, Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所粒子天体物理国家重点实验室、实验物理部及计算中心）；University of Chinese Academy of Sciences（中国科学院大学）；TIANFU Cosmic Ray Research Center（天府宇宙线研究中心）；University of Science and Technology of China（中国科学技术大学）；Yerevan State University（埃里温国立大学）；Max-Planck-Institut for Nuclear Physics（马克斯·普朗克核物理研究所）；Tsung-Dao Lee Institute & School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学李政道研究所暨物理与天文学院）；Center for Astrophysics, Guangzhou University（广州大学天体物理中心）
Recent observations by the Large High Altitude Air Shower Observatory (LHAASO) have paved the way for the observational detection of PeVatrons in the Milky Way Galaxy, thus revolutionizing the field of $γ$-ray astrophysics. In this paper, we study one such detected source, LHAASO J1908+0621, and explore the origin of multi-TeV $γ$-ray emission from this source. A middle-aged radio supernova remnant SNR G40.5-0.5 and a GeV pulsar PSR J1907+0602 are co-spatial with LHAASO J1908+0621. Dense molecular clouds are also found to be associated with SNR G40.5-0.5. We explain the multi-TeV $γ$-ray emiss…
We present a simple phenomenological model of hadronic interaction between protons accelerated in an old supernova remnant (SNR) and cold protons situated within the associated molecular clouds (MCs). The accelerated protons from the old SNR escaped the SNR shock front, and got injected into the MCs at an earlier time, producing ultra high energy gamma-rays and neutrinos through inelastic proton-proton interaction. We also take into account the acceleration and subsequent escape of electrons from the SNR shock front. The escaped electrons produce gamma-rays through various radiative cooling me…
Recently, the Large High Altitude Air Shower Observatory (LHAASO) reported the discovery of 12 ultrahigh-energy (UHE; $\mathrm{\varepsilon} \ge 100$ TeV) gamma-ray sources located in the Galactic plane. A few of these UHE gamma-ray emitting regions are in spatial coincidence with pulsar wind nebulae (PWNe). We consider a sample of five sources; two of them are LHAASO sources (LHAASO J1908+0621 and LHAASO J2226+6057) and the remaining three are GeV-TeV gamma-ray emitters. In addition, X-rays, radio observations, or upper limits are also available for these objects. We study multiwavelength radi…
The Crab nebula is a prominent pulsar wind nebula (PWN) detected in multiband observations ranging from radio to very high-energy (VHE) $γ$-rays. Recently, $γ$-rays with energies above $1 \mathrm{PeV}$ had been detected by the Large High Altitude Air Shower Observatory (LHAASO), and the energy of the most energetic particles in the nebula can be constrained. In this paper, we investigate the broadest spectral energy distribution of the Crab nebula and the energy distribution of the electrons emitting the multiwavelength nonthermal emission based on a one-zone time-dependent model. The nebula i…
TeV Gamma Rays and Neutrinos from Winds Driven by Radiatively Inefficient Accretion Flows of Low-Luminosity Active Galactic Nuclei
The University of Osaka（大阪大学）；The Ohio State University（俄亥俄州立大学）；The Pennsylvania State University（宾夕法尼亚州立大学）；Yukawa Institute for Theoretical Physics, Kyoto University（京都大学汤川理论物理研究所）
本研究针对LHAASO探测到的LLAGN NGC 4278宁静期TeV伽马射线，提出RIAF驱动风的新机制，建模重现其辐射，还可推广至Sgr A*，为LLAGN辐射机制提供新解释。
Interpreting Swift and NuSTAR Observations of the Low-Luminosity Active Galactic Nucleus NGC 4278 with Radiatively Inefficient Accretion Flows and Implications for Neutrino Emission
The Pennsylvania State University（宾夕法尼亚州立大学）；University of Utah（犹他大学）；Tohoku University（东北大学）
High-sensitivity X-ray polarimetric observations of black hole X-ray binaries, which will soon become available with the launches of space-borne X-ray observatories with sensitive X-ray polarimeters, will be able to put independent constraints on the black hole as well as the accretion flow, and possibly break degeneracies that cannot be resolved by spectral/timing observations alone. In this work we perform a series of general relativistic Monte-Carlo radiative transfer simulations to study the expected polarization properties of X-ray radiation emerging from lamp-post coronae in black hole X…
It has been long debated whether the high-energy gamma-ray radiation from the Crab nebula stems from leptonic or hadronic processes. In this work, we investigate the multi-band non-thermal radiation from the Crab pulsar wind nebula with the leptonic and leptonic-hadronic hybrid models, respectively. Then we use the Markov Chain Monte Carlo(MCMC) sampling technology and method of sampling trace to study the stability and reasonability of the model parameters according to the recent observed results and obtain the best-fitting values of parameters. Finally, we calculate different radiative compo…
Recent observations of VER J2227+608 reveal a broken power $γ$-ray spectrum with the spectral index increasing from $\sim 1.8$ in the GeV energy range to $\sim 2.3$ in the TeV range. Such a spectral break can be attributed to radiative energy loss of energetic electrons in the leptonic scenario for the $γ$-ray emission, which, in combination with characteristic age of the nearby pulsar, can be used to constrain magnetic field in the emission region. We show that the radio and X-ray observations can also be explained in such a scenario. In the hadronic scenario, the spectral break can be attrib…
Hadronic supercriticalities are radiative instabilities that appear when large amounts of energy are stored in relativistic protons. When the proton energy density exceeds some critical value, a runaway process is initiated resulting in the explosive transfer of the proton energy into electron-positron pairs and radiation. The runaway also leads to an increase of the radiative efficiency, namely the ratio of the photon luminosity to the injected proton luminosity. We perform a comprehensive study of the parameter space by investigating the onset of hadronic supercriticalities for a wide range …
Gamma-ray Emission from the S147 Region: Indication of Escaping Cosmic Rays Interacting with Molecular Clouds
Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台暗物质与空间天文重点实验室）；School of Astronomy and Space Science, University of Science and Technology of China（中国科学技术大学天文与空间科学学院）；Key Laboratory of Astroparticle Physics of Yunnan Province, Yunnan University（云南大学云南省天体物理重点实验室）
Investigating X-ray Emission from Radio-detected Broad- and Narrow-line Seyfert 1 Galaxies
Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Instituto de Estudios Astrofisicos Facultad de Ingenieria y Ciencias Universidad Diego Portales（迭戈帕托利亚斯大学工程与科学学院天体物理研究所）；College of Mathematics and Physics, Handan University（邯郸学院数理学院）
本研究通过拟合 XMM-Newton 光谱并结合多波段数据，比较了射电探测的 NLS1s 和 BLS1s 的 X 射线发射，发现 NLS1s 具有更陡的光子指数和更弱的 X 射线发射，差异源于其更早的演化阶段，并支持喷流相关的多波段辐射联系。
Constraining leptonic and hadronic gamma-ray emission from HESS J1825-137 and its environment
Universidade Tecnológica Federal do Paraná（巴拉那联邦技术大学）；Universidade Federal do Paraná (UFPR)（巴拉那联邦大学）；Universidade Federal do Espírito Santo（圣埃斯皮里图联邦大学）；Universidade Estadual de Londrina (UEL)（隆德里纳州立大学）；Universidade Federal da Integração Latino-Americana（拉丁美洲一体化联邦大学）
Physical origin of very-high-energy gamma rays from the low-luminosity active galactic nucleus NGC 4278 and implications for neutrino observations
Guangxi University（广西大学）；The Pennsylvania State University（宾夕法尼亚州立大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；TIANFU Cosmic Ray Research Center（天府宇宙线研究中心）；Tohoku University（东北大学）
