# The International Cosmic Ray Conference 2017

12-20 July 2017
BEXCO
Asia/Seoul timezone
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BEXCO

# [GA272] Very high energy emission from the hard spectrum sources HESS J1641-463, HESS J1741-302 and HESS J1826-130

## Speakers

• Ekrem Oguzhan ANGUNER

## Description

A recent study of the diffuse gamma-ray emission in the central molecular zone by using very high energy (VHE, E > 0.1 TeV) H.E.S.S. data suggests that the Galactic Center (GC) is the most plausible supplier of Galactic ultra-relativistic cosmic rays (CRs) up to the knee at about 10$^{15}$ eV (PeV). However, the GC might not be the only source capable to accelerate CRs up to PeV energies in the Galaxy. Here we present H.E.S.S. data analysis results and interpretation of three H.E.S.S. sources, with spectra extending beyond 10 TeV and relatively hard spectral indices compared with the average spectral index of HESS sources, namely HESS J1641-463, HESS J1741-302 and HESS J1826-130. Although the nature of these VHE gamma-ray sources is still open, their spectra suggest that the astrophysical objects producing such emission must be capable of accelerating the parental particle population up to at least energies of several hundreds of TeV. Assuming a hadronic scenario, dense gas regions can provide rich target material for accelerated particles to produce VHE gamma-ray emission via proton-proton interactions followed by a subsequent $pi^{0}$ decay. Thus, detailed investigations of the interstellar medium along the line of sight to all of these sources have been performed by using data from available atomic and molecular hydrogen surveys. The results point out the existence of dense interstellar gas structures coincident with the best fit positions of these sources. One can find possible hadronic models with CRs being accelerated close to the PeV energies to explain the gamma-ray emission from all of these sources, which suggests that a population of PeV CR accelerators might be active in the Galaxy.