The 27th European Cosmic Ray Symposium

Constraining the primary proton spectrum of the hadronic PeVatron candidate HAWC J1825-134

28 Jul 2022, 15:15

15m

oral GA Parallel 2

Speaker

Timur Dzhatdoev (Moscow State University)

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)].

Presentation materials

HAWCJ1825-134-ECRS-2022.pdf