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Recently, a few-degrees extended $\gamma$-ray halo in the direction of Geminga pulsar has been detected by HAWC, Milagro and Fermi-LAT. These observations can be interpreted with positrons ($e^+$) and electrons ($e^-$) accelerated by…

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

The slow particle diffusion in pulsar halos, inferred from TeV gamma-ray surface brightness profiles, is attributed to cross-field diffusion under the anisotropic diffusion model. This model assumes sub-Alfv\'enic interstellar turbulence in…

High Energy Astrophysical Phenomena · Physics 2025-07-17 Kai Yan , Sha Wu , Ruo-Yu Liu

In this letter we propose that the X-ray and the TeV observations in the vicinity of Geminga can be understood in the framework of anisotropic diffusion of injected electrons/positrons. This interpretation only requires the turbulence in…

High Energy Astrophysical Phenomena · Physics 2019-12-04 Ruo-Yu Liu , Huirong Yan , Heshou Zhang

Pulsar halos (also termed 'TeV halo') are a new class of $\gamma$-ray sources in Galaxy, which manifest as extended $\gamma$-ray emission around middle-age pulsars, as discovered around the Geminga pulsar, the Monogem pulsar and…

High Energy Astrophysical Phenomena · Physics 2024-02-01 Qi-Zuo Wu , Chao-Ming Li , Xuan-Han Liang , Chong Ge , Ruo-Yu Liu

Nearby pulsars within $\sim1\,{\rm kpc}$ are considered to be possible sources of 10-500 GeV cosmic-ray positron excess measured by PAMELA and AMS-02. A TeV halo around Geminga is detected by HAWC, and the measurements of its surface…

High Energy Astrophysical Phenomena · Physics 2026-02-25 Yu Meng , Yun-Feng Liang , Ben-Yang Zhu , Xiao-Na Sun , En-Wei Liang

Anisotropic diffusion is one of the potential interpretations for the morphology of the Geminga pulsar halo. It interprets the observed slow-diffusion phenomenon through a geometric effect, assuming the mean magnetic field direction around…

High Energy Astrophysical Phenomena · Physics 2023-08-02 Kun Fang , Hong-Bo Hu , Xiao-Jun Bi , En-Sheng Chen

LHAASO J0248$+$6021, a possible $\gamma$-ray pulsar halo associated with PSR J0248$+$6021 (J0248), exhibits a highly curved spectrum as revealed by LHAASO and Fermi-LAT measurements. We propose a direct interpretation of this large…

High Energy Astrophysical Phenomena · Physics 2026-05-19 Kun Fang

TeV Halos, extended regions of TeV gamma-ray emission around middle-aged pulsars, have recently been established as a new source class in gamma-ray astronomy. These halos have been attributed to relativistic electrons and positrons that…

TeV haloes are a recently discovered class of very high energy gamma-ray emitters. These sources consist of extended regions of multi-TeV emission, originally observed around the two well-known and nearby pulsars, Geminga and PSR B0656+14…

High Energy Astrophysical Phenomena · Physics 2024-09-04 Elena Amato , Sarah Recchia

Geminga is an enigmatic radio-quiet gamma-ray pulsar located at a mere 250 pc distance from Earth. Extended very-high-energy gamma-ray emission around the pulsar was discovered by Milagro and later confirmed by HAWC, which are both water…

High Energy Astrophysical Phenomena · Physics 2023-05-24 H. E. S. S. Collaboration , : , F. Aharonian , F. Ait Benkhali , J. Aschersleben , H. Ashkar , M. Backes , V. Barbosa Martins , R. Batzofin , Y. Becherini , D. Berge , K. Bernlöhr , B. Bi , M. Böttcher , C. Boisson , J. Bolmont , J. Borowska , M. Bouyahiaoui , F. Bradascio , R. Brose , F. Brun , B. Bruno , T. Bulik , C. Burger Scheidlin , F. Cangemi , S. Caroff , S. Casanova , J. Celic , M. Cerruti , P. Chambery , T. Chand , S. Chandra , A. Chen , J. Chibueze , O. Chibueze , G. Cotter , J. Damascene Mbarubucyeye , J. Devin , A. Djannati-Ataï , A. Dmytriiev , K. Egberts , S. Einecke , J. P. Ernenwein , K. Feijen , G. Fichet de Clairfontaine , M. Filipovic , G. Fontaine , M. Füssling , S. Funk , S. Gabici , Y. A. Gallant , S. Ghafourizadeh , G. Giavitto , L. Giunti , D. Glawion , J. F. Glicenstein , P. Goswami , G. Grolleron , M. -H. Grondin , L. Haerer , M. Haupt , G. Hermann , J. A. Hinton , W. Hofmann , T. L. Holch , M. Holler , D. Horns , Zhiqiu Huang , M. Jamrozy , F. Jankowsky , V. Joshi , I. Jung-Richardt , E. Kasai , K. Katarzyński , B. Khélifi , W. Kluźniak , Nu. Komin , K. Kosack , D. Kostunin , R. G. Lang , S. Le Stum , F. Leitl , A. Lemière , M. Lemoine-Goumard , J. -P. Lenain , F. Leuschner , T. Lohse , A. Luashvili , I. Lypova , J. Mackey , D. Malyshev , V. Marandon , P. Marchegiani , A. Marcowith , P. Marinos , G. Martí-Devesa , R. Marx , G. Maurin , P. J. Meintjes , M. Meyer , A. Mitchell , R. Moderski , L. Mohrmann , A. Montanari , E. Moulin , J. Muller , K. Nakashima , M. de Naurois , J. Niemiec , A. Priyana Noel , P. O'Brien , S. Ohm , L. Olivera-Nieto , E. de Ona Wilhelmi , M. Ostrowski , S. Panny , M. Panter , R. D. Parsons , G. Peron , D. A. Prokhorov , G. Pühlhofer , A. Quirrenbach , A. Reimer , O. Reimer , M. Renaud , B. Reville , F. Rieger , G. Rowell , B. Rudak , H. Rueda Ricarte , E. Ruiz-Velasco , V. Sahakian , H. Salzmann , A. Santangelo , M. Sasaki , F. Schüssler , H. M. Schutte , U. Schwanke , J. N. S. Shapopi , A. Sinha , H. Sol , A. Specovius , S. Spencer , Ł. Stawarz , S. Steinmassl , I. Sushch , H. Suzuki , T. Takahashi , T. Tanaka , T. Tavernier , A. M. Taylor , R. Terrier , C. Thorpe-Morgan , M. Tsirou , N. Tsuji , M. Vecchi , C. Venter , J. Vink , S. J. Wagner , R. White , A. Wierzcholska , Yu Wun Wong , M. Zacharias , D. Zargaryan , A. A. Zdziarski , A. Zech , S. Zouari , N. Żywucka

TeV halos are regions of enhanced photon emissivity surrounding pulsars. While multiple sources have been discovered, a self-consistent explanation of their radial profile and spherically-symmetric morphology remains elusive due to the…

High Energy Astrophysical Phenomena · Physics 2023-01-12 Pedro De La Torre Luque , Ottavio Fornieri , Tim Linden

Recently, the High Altitude Water Cherenkov (HAWC) collaboration reported the discovery of the TeV halo around the Geminga pulsar. The TeV emission is believed to originate from inverse Compton scattering of pulsar-injected…

High Energy Astrophysical Phenomena · Physics 2019-04-26 Ruo-Yu Liu , Chong Ge , Xiao-Na Sun , Xiang-Yu Wang

The HAWC Collaboration has recently reported the detection of bright and spatially extended multi-TeV gamma-ray emission from Geminga, Monogem, and a handful of other nearby, middle-aged pulsars. The angular profile of the emission observed…

High Energy Astrophysical Phenomena · Physics 2018-10-17 Dan Hooper , Tim Linden

High-energy particle transport in pulsar wind nebulae (PWNe) plays an essential role in explaining the characteristics revealed in multiwavelength observations. In this paper, the TeV-gamma-ray-emitting electrons in the Vela X PWN are…

High Energy Astrophysical Phenomena · Physics 2019-07-04 Yiwei Bao , Siming Liu , Yang Chen

Diffusive shock acceleration and diffusion propagation are essential components of the standard cosmic ray model. These theories are based on extensive observations of high-energy solar processes, providing substantial direct evidence in…

High Energy Astrophysical Phenomena · Physics 2026-05-19 Weikang Gao , Li-Zhuo Bao , Kun Fang , En-sheng Chen , Siming Liu , HongBo Hu

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

The discovery of extended TeV emission around the Geminga and PSR B0656+14 pulsars, with properties consistent with free particle propagation in the interstellar medium (ISM), has sparked considerable discussion on the possible presence of…

High Energy Astrophysical Phenomena · Physics 2020-04-29 G. Giacinti , A. M. W. Mitchell , R. López-Coto , V. Joshi , R. D. Parsons , J. A. Hinton

The extended $\gamma$-ray halos around pulsars are unique probe of transportation of high-energy electrons (and positrons) in vicinities of such pulsars. Observations of morphologies of several such halos indicate that particles diffuse…

High Energy Astrophysical Phenomena · Physics 2024-07-17 YingYing Guo , Qiang Yuan

Cosmic ray electrons and positrons are tracers of particle propagation in the interstellar medium (ISM). A recent measurement performed using H.E.S.S. extends the all-electron (electron+positron) spectrum up to 20TeV, probing very local…

High Energy Astrophysical Phenomena · Physics 2019-01-08 R. López-Coto , R. D. Parsons , J. A. Hinton , G. Giacinti

Pulsars convert a significant fraction of their total spin-down power into very high-energy electrons, leading to the formation of TeV halos. It is not yet known, however, whether these sources also efficiently accelerate electrons at lower…

High Energy Astrophysical Phenomena · Physics 2024-05-14 Dan Hooper , Elena Pinetti , Anastasia Sokolenko