Abstract:
Recently, the Large High Altitude Air Shower Observatory (LHAASO) reported the discovery of 12 ultrahigh-energy (UHE; ε
≥ 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 radiation from these
sources by considering a PWN origin, where the emission is powered by spin-down luminosity of the associated pulsars. In
this Leptonic emission model, the electron population is calculated at different times under the radiative (synchrotron and
inverse-Compton) and adiabatic cooling. We also include the onset of the reverberation phase for the PWN, by assuming radially
symmetric expansion. However, in this work, we find that multiwavelength emission can be interpreted before the onset of this
phase. The maximum energy of the electrons based on the spectral fit is found to be above 0.1 PeV and close to 1 PeV. For
LHAASO J2226+6057, using its observations in radio to UHE gamma-rays, we find that UHE gamma-rays can be interpreted
using electrons with maximum energy of 1 PeV. We estimate the upper limits on the minimum Lorentz factor of the electrons
and it also infers the minimum value of the pair-multiplicity of charged pairs.
