# The LHAASO PeVatron Bright Sky: What We Learned
## 3 Overview of the 12 LHAASO Sources
### LHAASO J1908+621  
LHAASO J1908+621 is one of the LHAASO sources (the others are the Crab Nebula, LHAASO J1825-1326, and LHAASO J2226+6057) detected with the highest significance at E \(>\) 100 TeV (17.2 \(\sigma\)) and for which there is a SED at UHE [43]. Its maximum energy is \(E_{M}\approx\) 450 TeV and it shows a spectral steepening, possibly due to photon-photon absorption. The potential TeV counterpart is the well-known MGRO J1908+06 [116] also detected by HESS [167], ARGO [168], VERITAS [169], and finally by HAWC at E \(>\) 56 TeV [21; 170], with an extension confirmed up to the highest energies. With an off-pulsed analysis, Fermi-LAT detected two GeV excesses corresponding with the LHAASO J1908+621 contours, Fermi J1906+0626, and 4 FGL J1906.2+0631 [171]. Possible associations include the middle-aged shell-type SNR G40.5-0.5, which has a MC complex in the surrounding [172; 173]; the PWN of the radio PSR J1907+0631; and finally the most powerful PSR J1907+0602 (with aspin-down luminosity sufficient to explain the VHE emission), all in the same region as LHAASO J1908+621 [131] (see Figure 10, left).  
In [173], the authors tried to model the whole HE spectrum, concluding that a leptonic or lepto-hadronic model was the most likely with respect to a purely hadronic one. These conclusions were confirmed also by [174], with a dominant hadronic component at the highest energies, and then by [175], with a leptonic component from the PWN J1907+0602 explaining the GeV-TeV component, and a hadronic component from the SNR/MC interaction explaining the UHE spectrum (see Figure 10, right). The one-component leptonic model was also the underdog in the time-dependent model developed in [176]. Only in [177] was a purely leptonic model favored, but this could have depended on the fact that their Fermi-LAT data analysis obtained GeV spectral points different from the ones used in  
Figure 9: LHAASO J1843-0338. (**Left**): Tibet AS\(\gamma\) significance map of TASG J1844-038 at E \(>\) 25 TeV [Figure from [162]]. (**Right**): SED of TASG J1844-038, assuming that the LHAASO data point is also correlated with this source [Figure from [162]].  
the other papers [172]. A crosscheck in the GeV band is needed to better understand this complex region.  
In the IceCube neutrino analysis carried out by [64], LHAASO J1908+621 was constrained to be leptonic dominant up to 200 TeV. A Bayesian approach, however, could not constrain this source, stressing how these estimations are strongly biased by statistical methods [35]. In [36], the authors estimated the neutrino fluxes expected in the case where LHAASO J1908+621 was a SNR with a completely hadronic emission, concluding that the IceCube sensitivity is insufficient to detect possible neutrino emissions. However, a low-significance neutrino emission seemed to come from this region [37], supporting the (hadronic) PeVatron nature of this source.  
The higher sensitivity of future neutrino experiments, together with the higher angular resolution of future IACTs, will give a fundamental boost to the understanding of this source. This source will be observable by the ASTRI Mini-Array site for a total of about 550 h per year, and simulations have shown that already with 100 hours, a high-significance spectrum up to 300 TeV can be obtained, perfectly correlated with the one detected by LHAASO [62]. Moreover, the ASTRI Mini-Array angular resolution will be able to resolve the possible counterparts in the \(\gamma\)-ray error box [178].