Cao Z.Aharonian F.AxikeguBai Y.X.Bao Y.W.Bastieri D.Bi X.J.Bi Y.J.Bian W.Bukevich A.V.Cao Q.Cao W.Y.Cao Z.Chang J.Chang J.F.Chen A.M.Chen E.S.Chen H.X.Chen L.Chen L.Chen L.Chen M.J.Chen M.L.Chen Q.H.Chen S.Chen S.H.Chen S.Z.Chen T.L.Chen Y.Cheng N.Cheng Y.D.Chu M.C.Cui M.Y.Cui S.W.Cui X.H.Cui Y.D.Dai B.Z.Dai H.L.Dai Z.G.DanzengluobuDong X.Q.Duan K.K.Fan J.H.Fan Y.Z.Fang J.Fang J.H.Fang K.Feng C.F.Feng H.Feng L.Feng S.H.Feng X.T.Feng Y.Feng Y.L.Gabici S.Gao B.Gao C.D.Gao Q.Gao W.Gao W.K.Ge M.M.Ge T.T.Geng L.S.Giacinti G.Gong G.H.Gou Q.B.Gu M.H.Guo F.L.Guo J.Guo X.L.Guo Y.Q.Guo Y.Y.Han Y.A.Hannuksela O.A.Hasan M.He H.H.He H.N.He J.Y.He Y.Hor Y.K.Hou B.W.Hou C.Hou X.Hu H.B.Hu Q.Hu S.C.Huang C.Huang D.H.Huang T.Q.Huang W.J.Huang X.T.Huang X.Y.Huang Y.Huang Y.Y.Ji X.L.Jia H.Y.Jia K.Jiang H.B.Jiang K.Jiang X.W.Mahidol University2025-02-202025-02-202025-07-01Science China: Physics, Mechanics and Astronomy Vol.68 No.7 (2025)16747348https://repository.li.mahidol.ac.th/handle/20.500.14594/105355The ultra-high-energy (UHE) gamma-ray source 1LHAASO J0007+7303u is positionally associated with the composite SNR CTA1 that is located at high Galactic Latitude b ≈ 10.5°. This provides a rare opportunity to spatially resolve the component of the pulsar wind nebula (PWN) and supernova remnant (SNR) at UHE. This paper conducted a dedicated data analysis of 1LHAASO J0007+7303u using the data collected from December 2019 to July 2023. This source is well detected with significances of 21σ and 17σ at 8–100 TeV and >100 TeV, respectively. The corresponding extensions are determined to be 0.23°±0.03° and 0.17°±0.03°. The emission is proposed to originate from the relativistic electrons accelerated within the PWN of PSR J0007+7303. The energy spectrum is well described by a power-law with an exponential cutoff function dN/dE=(42.4±4.1)(E20TeV)−2.31±0.11exp(−E110±25TeV) TeV−1 cm−2 s−1 in the energy range from 8 to 300 TeV, implying a steady-state parent electron spectrum dNe/dEe∝(Ee100TeV)−3.13±0.16exp[(−Ee373±70TeV)2] at energies above ≈ 50 TeV. The cutoff energy of the electron spectrum is roughly equal to the expected current maximum energy of particles accelerated at the PWN terminal shock. Combining the X-ray and gamma-ray emission, the current space-averaged magnetic field can be limited to ≈ 4.5 µG. To satisfy the multi-wavelength spectrum and the γ-ray extensions, the transport of relativistic particles within the PWN is likely dominated by the advection process under the free-expansion phase assumption.Physics and AstronomyArticleSCOPUS10.1007/s11433-024-2479-42-s2.0-8521757354618691927