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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

In recent years, the number of known sources emitting very- and ultra-high-energy gamma-rays has increased significantly thanks to facilities such as LHAASO and HAWC. Many of the observed sources are still unidentified or poorly constrained…

High Energy Astrophysical Phenomena · Physics 2025-09-19 Michela Rigoselli , Sarah Recchia , Alberto Bonollo , Silvia Crestan , Giada Peron , Andrea Giuliani , Sandro Mereghetti

The High-Altitude Water Cherenkov Telescope (HAWC) has detected TeV halos associated with two nearby pulsars/pulsar wind nebulae (PWN) -- Geminga and B0656+14. These TeV halos extend up to tens of pc from the central accelerators,…

High Energy Astrophysical Phenomena · Physics 2025-02-26 Youyou Li , Oscar Macias , Shinichiro Ando , Jacco Vink

Diffusive TeV gamma-ray emissions have been recently discovered extending beyond the pulsar wind nebulae of a few middle-aged pulsars, implying that energetic electron/positron pairs are escaping from the pulsar wind nebulae and radiating…

High Energy Astrophysical Phenomena · Physics 2022-11-09 Ruo-Yu Liu

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

The study of extended $\gamma$-ray sources usually assumes symmetric diffusion of cosmic rays. However, recent observations of multiple sources near single pulsars and significant offsets between TeV halo centroids and their parent pulsars…

High Energy Astrophysical Phenomena · Physics 2025-09-09 Yiwei Bao , Gwenael Giacinti , Ruo-Yu Liu , Hai-Ming Zhang , Yang Chen

Observations by HAWC indicate that many young pulsars (including Geminga and Monogem) are surrounded by spatially extended, multi-TeV emitting regions. It is not currently known, however, whether TeV emission is also produced by recycled,…

High Energy Astrophysical Phenomena · Physics 2018-08-15 Dan Hooper , Tim Linden

The H.E.S.S. telescope has recently detected the total electron-plus-positron ($e^+e^-$) flux up to 40 TeV, finding it to be a featureless and steeply-falling power-law above 1 TeV. This result is in stark tension with standard one-zone…

High Energy Astrophysical Phenomena · Physics 2025-03-25 Isabelle John , Tim Linden

The gamma-ray halo around Geminga is formed owing to the slow diffusion of the electrons released by the Geminga PWN. The latest HAWC and HESS observations exhibit complex features in the TeV gamma-ray spectrum of the Geminga halo. We first…

High Energy Astrophysical Phenomena · Physics 2022-05-18 Kun Fang , Xiao-Jun Bi

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

Detailed observation by the High-Altitude Water Cerenkov Observatory of the regions within about 20 pc of the nearby Geminga and PSR B0656+14 pulsars have suggested the need for the diffusion coefficient of 10-100 TeV leptons yielding the…

High Energy Astrophysical Phenomena · Physics 2018-07-20 J J Quenby

The TeV $\gamma$-ray halo around the Geminga pulsar is an important indicator of cosmic-ray (CR) propagation in the local zone of the Galaxy as it reveals the spatial distribution of the electrons and positrons escaping from the pulsar.…

High Energy Astrophysical Phenomena · Physics 2021-03-31 Sheng-Hao Wang , Kun Fang , Xiao-Jun Bi , Peng-Fei Yin

Measurements of the nearby pulsars Geminga and B0656+14 by the HAWC and Milagro telescopes have revealed the presence of bright TeV-emitting halos surrounding these objects. If young and middle-aged pulsars near the Galactic Center transfer…

High Energy Astrophysical Phenomena · Physics 2017-12-12 Dan Hooper , Ilias Cholis , Tim Linden

Pulsar halos are produced by electrons and positrons diffusing in the interstellar medium around their parent pulsar wind nebulae. Recent observations by HAWC and LHAASO have revealed asymmetric morphologies in the halos surrounding Geminga…

High Energy Astrophysical Phenomena · Physics 2026-05-25 Si-Zhe Wu , Chao-Ming Li , Ruo-Yu Liu

Nearby pulsars have been suggested as sources of $\sim$TeV $e^+/e^-$ Cosmic Ray (CR) excess on Earth. The High-Altitude Water Cherenkov Observatory (HAWC) detected extended TeV emission regions in the direction of two nearby middle-aged…

High Energy Astrophysical Phenomena · Physics 2019-01-30 Xiaping Tang , Tsvi Piran

Extended $\gamma$-ray emission has been observed around several nearby pulsars and is commonly interpreted as inverse-Compton radiation produced by relativistic electrons and positrons diffusing in the surrounding interstellar medium. In…

High Energy Astrophysical Phenomena · Physics 2026-04-01 Qian Zhong

TeV haloes are extended sources of very-high-energy gamma rays found around some middle-aged pulsars. The emission spanning several tens of parsecs suggests an efficient confinement of the ultra-relativistic lepton pairs produced by pulsars…

High Energy Astrophysical Phenomena · Physics 2026-02-11 Lioni-Moana Bourguinat , Carmelo Evoli , Pierrick Martin , Sarah Recchia

We investigate the asymmetric propagation of 100 TeV electrons (whose radiation mainly concentrates on 20--30 TeV) in turbulent magnetic fields around pulsars, using GPU-accelerated simulations to explore their trajectories and interactions…

High Energy Astrophysical Phenomena · Physics 2026-02-03 Yiwei Bao , Ruo-Yu Liu , Gwenael Giacinti , Hai-Ming Zhang , Yang Chen

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

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