# The LHAASO PeVatron Bright Sky: What We Learned
## 3 Overview of the 12 LHAASO Sources
### LHAASOJ0534+2202 (Crab Nebula)  
LHAASO J0534+2202 is the only LHAASO candidate PeVatron with a specified counterpart, the Crab Nebula. LHAASO detected its emission with the highest significance, \(\sigma=17.8\). Its maximum energy was about \(E_{M}\approx 900\) TeV during its first detection by KM2A and WFCTA [43] but, in a second shower detected by KM2A one year later, this reached \(E_{M}=1.12\pm 0.09\) PeV [130]. Figure 6: The well-known table with the list of the energetic astrophysical objects possibly associated with each LHAASO source. Other information such as coordinates, maximum energy, and significance can be found in [43] and also in Figure 19 (Figure from [43], reproduced with permission from [43], Springer Nature, 2023). The Crab Nebula is one of the most studied sources of our galaxy in every electromagnetic band, from radio to \(\gamma\)-ray (see [69], for a recent and complete review). In the HE band, its flaring nature at MeV energies [134; 135; 136] was a breakthrough for all theoretical models but even its steady VHE \(\gamma\)-ray emission is very interesting. Indeed, its synchrotron emission was one of the first pieces of evidence for the presence of PeV electrons in its environment [137] and its Pevatron nature was confirmed by the HAWC [20] and Tibet AS\(\gamma\)[23] results, which detected it at \(E>150\) TeV; only the sensitivity of water and air shower detectors can reach these extreme energies. The very high sensitivity at UHE of the LHAASO KM2A (\(\sim\)10\({}^{-14}\) erg cm\({}^{2}\)s\({}^{-1}\) at \(E>50\) TeV in 1 yr) showed, for the first time, that the \(\gamma\)-ray component of its spectrum extended up to 1.1 PeV, transforming it into a super-PeVatron [130]. Following what we said in Section 2.3, the Crab Nebula is one of the youngest and most powerful PWNs and, consequently, the maximum energy of its \(\gamma\)-ray emission is radiation limited. This means that its detection at 1.1 PeV implies an acceleration rate \(\eta_{e}\approx 0.16\), three orders of magnitude greater than that in SNRs [43; 130]. After the LHAASO detection, the main issue connected to the super-PeVatron nature of the Crab Nebula is related to its acceleration mechanism but also to the possibility of a contribution from a hadronic component. Even before this discovery, the possibility of a contribution from hadrons had been investigated (see [138], and reference therein) but now, around 1 PeV, the LHAASO spectrum shows a hardening of the spectrum that is really challenging to explain with a leptonic component [130]. The LHAASO error bars are very large and, consequently, this hardening needs to be confirmed, but if it is, this will support the idea of a UHE hadronic component: a component that cannot explain the overall \(\gamma\)-ray luminosity but that can have a non-negligible contribution at the highest energies, with the condition of proton confinement in the nebula [130]. Recent models estimated that this hardening is compatible with a quasi-monochromatic distribution of protons around 10 PeV [69; 139], to be added to the confirmed leptonic distribution. The Lorentz factor and the spin-down luminosity of protons are two of the most important parameters that characterize this component [62]. Several theoretical models for constraining this hypothetical hadronic component are being developed [115; 138] (see Figure 7), and future instruments such as the ASTRI Mini-Array and CTA will be fundamental for confirming a lepto-hadronic model of the \(\gamma\)-ray emission from the Crab Nebula. In the ASTRI Mini-Array core science paper [62], a simulation of a Crab spectrum up to 300 TeV was produced, showing how the ASTRI Mini-Array could be decisive in constraining the likely hadronic component at the highest energies.