Abstract
The presence of dense clumps in the environment where a supernova remnant expands might have a strong impact in shaping the observed hadronic gamma-ray spectrum. A detailed numerical study about the penetration of relativistic protons into clumps which are engulfed by a supernova remnant shock is here presented, taking into account the magneto-hydrodynamical properties of the background plasma. This has strong implications for the formation of the spectrum of hadronic gamma rays, which does not reflect anymore the acceleration spectrum of protons, resulting substantially modified by propagation effects. A hadronic scenario including dense clumps inside the remnant shell is shown to adequately reproduce the broadband gamma-ray spectrum of the Galactic supernova remnant RX J1713-3946.7 from GeV to TeV energies.
Highlights
During the latest years, numerous detections of supernova remnants (SNRs) in TeV gamma rays have confirmed the theoretical predictions that SNRs can operate as powerful CR accelerators
Visf/t√heχs=ho1c.k4 speed × 106 is v = cm s−1 vsz, [1]. It propagates inside the clump with The interesting time interval for the a velocity evolution of the background plasma is about 300 years from the first shock-clump interaction, as for larger times clumps will have been crossed by the contact discontinuity and they will soon be emptied of CRs
Consequence, low-energy accelerated particles needs more time to penetrate the clump compared to high-energy ones, resulting into a significant hardening of the particle energy spectrum inside clumps with respect to the acceleration spectrum
Summary
Numerous detections of supernova remnants (SNRs) in TeV gamma rays have confirmed the theoretical predictions that SNRs can operate as powerful CR accelerators. Dense molecular clouds constitute potential sources of both gamma rays and neutrinos, in that the protons accelerated at the SNR shock might interact with the dense gas contained in clumps (in the so-called pp interaction) and produce both neutral pions and charged pions. This spectrum results much harder than that in the diffuse inter-clump medium: as a consequence, the gamma-ray spectrum resulting from pp interactions will reflect this hardening.
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