# The LHAASO PeVatron Bright Sky: What We Learned
## 3 Overview of the 12 LHAASO Sources
### LHAASO J2226+6057  
LHAASO J2226+6057 is one of the four LHAASO sources (the other are the Crab Nebula, LHAASO J1825-1326 and LHAASO J1908+621) detected with the highest significance at E \(>\) 100 TeV (13.6 \(\sigma\)) and for which there is a SED at UHE. Its maximum energy is \(E_{M}\approx 570\) TeV and it shows spectral steepening, maybe due to photon-photon absorption [43; 131]. Its TeV counterparts are VER J2227+608/HAWC J2227+610 [131], and there are two possible sources explaining this VHE/UHE emission: the SNR G106.3+2.7, with the associated MC, and the Boomerang PWN, associated with the PSR J2229+6141. The SNR is located in the \"tail\" of the VHE emission, with the PWN on the \"head\". The UHE detection by HAWC [199], Tibet AS\(\gamma\)[104], and finally by LHAASO [43] has a low angular resolution and, consequently, we were not able to say if it is from the head or the tail region. Recently, a 12-year Fermi-LAT GeV analysis of the region showed that at the highest energies (10-500 Gev), only the tail is emitting \(\gamma\)-ray (see Figure 16, top left) and a hadronic model from the SNR/MC interaction can explain the entire HE/VHE/UHE spectrum [54]. Recently, the MAGIC collaboration resolved the VHE/UHE emission and detected E \(>\) 10 TeV only from the tail region[52; 200], leaning towards a hadronic explanation of the \(\gamma\)-ray emission [199; 200], and linked to the SNR/MC interaction (or MC illumination form CRs escaping from the SNR [53]). The hadronic model used by the MAGIC collaboration also took into account the GeV Fermi-LAT data points from the tail region from [201] (consistent with the more recent results from [54]) (see Figure 16, top right). The same detection was explained using hadronic emission, but from the PWN and not from the SNR, by [201], due to the hard spectral index and low energy content of CRs. A PWN origin was also investigated by [55], concluding that, if a part of the UHE \(\gamma\)-ray emission comes from the PWN, it has to be of hadronic origin. Figure 15: LHAASO J2108+5157. (**Left**): significance map around LHAASO J2108+5157 as observed by KM2A at E \(>\) 100 TeV [Figure from [195], © AAS. Reproduced with permission.]. (**Right**): the leptonic (top) and hadronic (bottom) components that can explain the multiwavelength SED of this source in [198] (Figure from [198]). The real origin of the hadronic emission will only be understood with a deep analysis of the microphysics of the region but, regardless of a PWN or SNR origin, a hadronic origin is also supported by the analysis of nonthermal X-ray radiation [202; 203], detected everywhere but with an enhancement of the luminosity in the head region, and well correlated with the radio emissions but not with the \(\gamma\)-ray emissions. Nevertheless, there have been some works that analyzed a possible leptonic or lepto-hadronic origin of UHE emissions of LHAASO J2226+6057. In [204], before the LHAASO and Tibet AS\(\gamma\) detection, the entire spectrum from VER J2227+608 was explained with both leptonic and hadronic scenarios, and the authors concluded that only UHE data can discern the two models. However, an overlap of the later LHAASO and Tibet AS\(\gamma\) data on both their models makes it clear that neither model is confirmed (see Figure 16, bottom), requiring a further analysis with constraints on parameters computed using the LHAASO results. In both [176; 205], the authors developed a simplistic one-zone leptonic model (but complete with reverberation effect and PWN age estimation), assuming that the UHE emission comes from the Boomerang PWN. They obtained a good fit but a challenging low value for the magnetic field and a PWN size too large, maybe due to the very simple model used. It is clear that this source would be very interesting for future IACTs such as ASTRI Mini-Array and CTA. Both the collaborations have made simulations of this region, in order to evaluate the contribution of these two instruments to understanding it.