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The origin of the positron excess is one of the most intriguing mysteries in astroparticle physics. The recent discovery of extended $\gamma$-ray halos around the pulsars Geminga, Monogem and PSR J0621+3755 have brought indirect evidence…

High Energy Astrophysical Phenomena · Physics 2022-12-07 Donglin Wu

Recent gamma-ray observations reveal inhomogeneous diffusion of cosmic rays (CRs) in the interstellar medium (ISM). This is expected as the diffusion of CRs depends on the properties of turbulence, which can vary widely in the multi-phase…

High Energy Astrophysical Phenomena · Physics 2021-12-15 Siyao Xu

Pulsars are observed to emit bright and spatially extended emission at multi-TeV energies. Although such "TeV halos" appear to be an approximately universal feature of middle-aged pulsars, there remains much to be understood about these…

High Energy Astrophysical Phenomena · Physics 2023-12-19 Dan Hooper , Elena Pinetti , Anastasia Sokolenko

We simulate the neutrino and $\gamma$-ray emissions of the Galaxy which are originated from the hadronic scattering of cosmic rays (CR) with the interstellar medium (ISM). Rather than assuming a uniform CR density, we estimate the spatial…

Astrophysics · Physics 2010-10-27 Carmelo Evoli , Dario Grasso , Luca Maccione

A new study of the diffuse Galactic gamma-ray continuum radiation is presented, using a cosmic-ray propagation model which includes nucleons, antiprotons, electrons, positrons, and synchrotron radiation. Our treatment of the inverse Compton…

Astrophysics · Physics 2009-10-31 A. W. Strong , I. V. Moskalenko , O. Reimer

We attempt to interpret the cosmic-ray positron excess by injection from the nearby pulsar Geminga, assuming a two-zone diffusion scenario and an injection spectrum with a low energy cutoff. Since the high energy positrons and electrons…

High Energy Astrophysical Phenomena · Physics 2022-09-27 Guang-Yao Zhou , Zhao-Huan Yu , Qiang Yuan , Hong-Hao Zhang

Cosmic rays (CRs) interact with turbulent magnetic fields in the intestellar medium, generating nonthermal emission. After many decades of studies, the theoretical understanding of their diffusion in the ISM continues to pose a challenge.…

High Energy Astrophysical Phenomena · Physics 2025-07-15 Lucas Barreto-Mota , Elisabete M. de Gouveia Dal Pino , Siyao Xu , Alexandre Lazarian

The spectral data on the diffuse Galactic gamma-rays, at medium and high latitudes (|b| > 10) and energies of 1-100 GeV, recently published by the Fermi Collaboration are used to produce a novel study on the gamma-ray emissivity in the…

High Energy Astrophysical Phenomena · Physics 2011-10-28 Maryam Tavakoli , Ilias Cholis , Carmelo Evoli , Piero Ullio

The HAWC Gamma-Ray Observatory has reported the discovery of TeV gamma-ray emission extending several degrees around the positions of Geminga and B0656+14 pulsars. Assuming these gamma rays are produced by inverse Compton scattering off…

High Energy Astrophysical Phenomena · Physics 2019-08-13 F. Salesa Greus , S. Casanova , B. Dingus , R. Lopez-Coto , H. Zhou

The High Altitude Water Cherenkov (HAWC) telescope recently observed extended emission around the Geminga and PSR~B0656+14 pulsar wind nebulae (PWNe). These observations have been used to estimate cosmic-ray (CR) diffusion coefficients near…

High Energy Astrophysical Phenomena · Physics 2019-07-17 Gudlaugur Johannesson , Troy A. Porter , Igor V. Moskalenko

The recently identified source class of pulsar haloes may be numerous and bright enough in the TeV range to constitute a large fraction of the sources that will be observed with the Cherenkov Telescope Array (CTA). In this work, we quantify…

High Energy Astrophysical Phenomena · Physics 2023-03-15 Christopher Eckner , Veronika Vodeb , Pierrick Martin , Gabrijela Zaharijas , Francesca Calore

Interstellar magnetic field is essential in various astrophysical phenomena and processes. Pulsar halos are a recently discovered class of TeV gamma-ray sources formed by escaping electrons/positrons from pulsars. The morphology of the halo…

High Energy Astrophysical Phenomena · Physics 2026-01-23 Chao-Ming Li , Ruo-Yu Liu , Huirong Yan

Numerous extended sources around Galactic pulsars have shown significant $\gamma$-ray emission from GeV to TeV energies, revealing hundreds of TeV energy electrons scattering off of the underlying photon fields through inverse Compton…

High Energy Astrophysical Phenomena · Physics 2021-12-07 Mattia Di Mauro , Silvia Manconi , Michela Negro , Fiorenza Donato

Various studies have implied the existence of a gaseous halo around the Galaxy extending out to 100 kpc. Galactic cosmic rays (CRs) that propagate to the halo, either by diffusion or by convection with the possibly existing large-scale…

High Energy Astrophysical Phenomena · Physics 2019-01-30 Ruo-Yu Liu , Huirong Yan , Xiang-Yu Wang , Shi Shao , Hui Li

Recent observations have detected extended TeV gamma-ray emission surrounding young and middle-aged pulsars. The morphology of these "TeV halos" requires cosmic-ray diffusion to be locally suppressed by a factor of ~100-1000 compared to the…

High Energy Astrophysical Phenomena · Physics 2018-09-27 Carmelo Evoli , Tim Linden , Giovanni Morlino

The Vela and Geminga pulsars are rotation powered neutron stars, which have been identified in various spectral domains, from the near-infrared to hard $\gamma$-rays. In the near-infrared they exhibit tentative emission excesses, as…

Solar and Stellar Astrophysics · Physics 2011-11-16 Andrey A. Danilenko , Dmitry A. Zyuzin , Yuri A. Shibanov , Sergey V. Zharikov

Pulsar halos are a recently identified class of TeV $\gamma$-ray sources, offering valuable insights into the evolution of pulsar systems at the highest energies. However, only a handful of such sources have been detected so far, making…

High Energy Astrophysical Phenomena · Physics 2025-10-06 Tina Wach , Alison M. W. Mitchell

It has long been suggested that nearby pulsars within $\sim 1 \,{\rm kpc}$ are the leading candidate of the 10-500 GeV cosmic-ray positron excess measured by PAMELA and other experiments. The recent measurement of surface brightness profile…

High Energy Astrophysical Phenomena · Physics 2019-06-26 Shao-Qiang Xi , Ruo-Yu Liu , Zhi-Qiu Huang , Kun Fang , Xiang-Yu Wang

Observations have shown that spatially extended "TeV halos" are a common (and potentially generic) feature surrounding young and middle-aged pulsars. However, their morphology is not understood. They are larger than the "compact" region…

High Energy Astrophysical Phenomena · Physics 2022-06-22 Payel Mukhopadhyay , Tim Linden

The LHAASO Collaboration has recently reported a measurement of the diffuse gamma-ray emission from the Galactic Plane at energies between 10 TeV and 1 PeV. While this emission is brighter than that expected from cosmic-ray interactions in…

High Energy Astrophysical Phenomena · Physics 2024-10-18 Ariane Dekker , Ian Holst , Dan Hooper , Giovani Leone , Emily Simon , Huangyu Xiao