On the synchrotron origin of MeV-GeV emission of Crab Nebula: Explains from LHAASO's Observation

Crab Nebula is the standard candle for high-energy gamma-ray astronomy showing a stable emission over a long period of time. At relatively lower energy, i.e., in the MeV-GeV gamma-ray band, however, the nebule presents flares from time to time, lasting over a wide range of durations from hours up to months. While the MeV-GeV emission of Crab Nebula is believed to arise from the synchrotron radiation of relativistic electrons/positrons, the cutoff frequency of the spectrum during flares sometimes extends beyond the so-called synchrotron burn-off limit. Some previous studies explained the flares as the Doppler-boosted synchrotron emission from newly ejected blobs which move relativistically toward observers. We aim to test this model by comparing the expected inverse Compton (IC) radiation from the blob, which is supposed to appear in the ultrahigh-energy gamma-ray band, with the measurement of LHAASO. By doing so, we may impose constraints on some key parameters of the model. Based on the obtained constraints, we discuss the origin of the MeV-GeV emission of Crab Nebula.