Speaker
Description
The $\gamma$-ray spectrum of the Galactic source HAWC J1825-134 measured with HAWC [Albert et al., ApJ Lett., 907, L30 (2021)] extends beyond 200 TeV and does not reveal a knee or a cutoff. HAWC J1825-134 is among the best candidates for hadronic PeVatrons --- the objects able to accelerate protons up to the energy of at least 1 PeV. However, this source is situated in a crowded region of the $\gamma$-ray sky, greatly complicating the analysis.
Using the publicly available dataset of the Fermi-LAT space $\gamma$-ray telescope, we dissect the region around HAWC J1825-134 and eventually derive upper limits on the intensity of the source in the 1 GeV--1 TeV energy range. We show that only a very hard ($\gamma_{p}$<1.5) primary proton spectrum at $E_{p}$<10 TeV describes the Fermi-LAT data set well. Very hard $\gamma$-ray spectra below several TeV could represent a useful signature of Galactic hadronic PeVatrons.
A simple power-law-exponential cutoff spectrum could in principle describe the combined HAWC and Fermi-LAT data sets reasonably well for $\gamma_{p}\approx$1.5 and the cutoff energy $E_{p-c}\approx$500 TeV. More details could be found in [Dzhatdoev et al., ApJ, 929, 25 (2022)].
