# The LHAASO PeVatron Bright Sky: What We Learned
## 3 Overview of the 12 LHAASO Sources
### LHAASO J1839-0545  
LHAASO J1839-0545 was detected by LHAASO with an \(E_{M}\approx 200\) TeV in a very complex region. The two challenging potential TeV counterparts are HESS J1841-055 and 2 HWC J1837-065/HESS J1837-069/MAGIC J1837-073 [43; 131].  
The first, HESS J1841-055, was revealed by HESS in 2007 as an extended TeV source (\(\sim\)0.4\({}^{\circ}\)) [151] and then confirmed by HAWC [117] and ARGO [152], but it does not have a counterpart and up to now remains an unidentified source. In 2022, the MAGIC collaboration confirmed a TeV detection coincident with this HESS detection, finding some hot-spots in the extended emission that could indicate the presence of different sources in the same region that had not been resolved so far [153; 154]. Their analysis considered both PWN and SNR (the middle-aged G26.6-01) origins of the TeV emission as plausible, due to the presence of a dense MC in the surroundings. The spectrum produced through Fermi-LAT and MAGIC data analysis, however, only extended up to E \(<\) 10 TeV, with an evident cutoff  
Figure 8: LHAASO J1825-1326. (**Top Left**): HESS excess count map from [22] adapted with the addition of the LHAASO centroid and a rough estimation of the extension of the LHAASO detection from the image in [43] (white circle). (**Top right**): HESS 1-10 TeV excess map from [149] adapted by [43; 128] and with the addition of the LHAASO centroid and its extension from [43] (orange circle). The red ellipse indicates the Eel PWN. In this way, the reason why the association of the LHAASO emission is so challenging is evident. (**Bottom**): Spectrum of HESS J1825-137 from [22] with the LHAASO data points from [43] overlain. Reproduced with permission from [43], Springer Nature, 2023.  
at larger energies. Consequently, this evidence could exclude the association of LHAASO J1839-0545 with this complex source.  
On the contrary, HESS J1837-069 is more interesting for the interpretation of the LHAASO emissions. This was first detected by HESS during its Galactic Plane Survey [131] and then by HAWC [117] and MAGIC [155], and it is postulated to be associated with the PWN of the PSR J1838-0655 [131]. A very detailed study of that region by the MAGIC collaboration at GeV-TeV energies [156] found that the TeV emission coincident with the HESS J1837-069 can be interpreted as a hadronic emission, due to runaway CRs from that source with an MC at the location of MAGIC J1837-073. In this model, a maximum energy up to 70 TeV is considered reachable; LHAASO detected this source up to 200 TeV, maybe giving an important boost to that interpretation.  
Nevertheless, there is a further interesting hypothesis. In 2017, a deep analysis of Fermi-LAT data detected from the G25 region (the region that also includes the two HESS sources) seemed to indicate that there is an extended OB association, G25.18+0.26, with very similar characteristics and behavior to the Cygnus Cocoon region [157] (see Paragraph dedicated to Section 3.10). The spectrum from this region does not show any bending and could be a candidate for the TeV emission detected in this region. The very low LHAASO angular resolution also does not allow excluding this possible association, which could be another confirmation of the important role of MSCs in CR acceleration.  
As shown in [156], the future IceCube-Gen2 will have the necessary sensitivity to detect possible neutrino emissions from this source, confirming or excluding the hadronic origin of this TeV emission.