Theory of cosmic ray and γ-ray production in the supernova remnant RX J0852.0-4622

Abstract

Aims. The properties of the Galactic supernova remnant (SNR) RX J0852.0-4622 are theoretically analysed.Methods. An explicitly time-dependent, nonlinear kinetic model of cosmic ray (CR) acceleration in SNRs is used to describe the properties of SNR RX J0852.0-4622, the accelerated CRs, and the nonthermal emission. The source is assumed to be at a distance of ≈1 kpc in the wind bubble of a massive progenitor star. An estimate of the thermal X-ray flux in this configuration is given. Results. We find that the overall synchrotron spectrum of RX J0852.0-4622 as well as the filamentary structures in hard X-rays lead to an amplified magnetic field B > 100 μG in the SNR interior. This implies that the leptonic very high energy (VHE) γ-ray emission is suppressed, and that the VHE γ-rays are hadronically dominated. The energy spectrum of protons produced over the lifetime of the remnant until now may well reach "knee" energies. The derived γ-ray morphology is consistent with the HESS measurements. The amount of energy in energetic particles corresponds to about 35% of the hydrodynamic explosion energy. A remaining uncertainty concerns the thermal X-ray flux at 1 keV. A rough estimate, which is possibly not quite appropriate for the assumed wind bubble configuration, is found to be higher than the nonthermal flux at this energy. Conclusions. It is concluded that this SNR expanding into the wind bubble of a massive star in a dense gas environment can be a hadronic γ-ray source that is consistent with all existing multiwavelength constraints, except possibly the thermal X-ray emission.

Nonthermal and thermal emission from the supernova remnant RX J1713.7-3946

“…As a result, shock modification by the pressure gradient of the accelerating particles becomes possible everywhere on the shock surface. This reasoning follows the discussion in Berezhko et al (2009) with the conclusion that SNRs propagating into wind bubbles should have their forward shock modified everywhere. Technically, this implies that the SNR becomes spherically symmetric and the correction factor f re < 1 (Völk et al 2003) on the spherically symmetric solution reaches unity.…”

“…We use the results of numerical calculations performed by Hamilton et al (1983) with some corrections. These mean that the X-ray emissivity of the remnant is reduced by the ratio R em = EM b /EM S of the emission measure EM b for our bubble solution to the emission measure for the classical Sedov solution EM S , which corresponds to a uniform ambient gas density N g (R s ) (Berezhko et al 2009). …”

“…As for the case of RX J0852.0-4622 (Berezhko et al 2009) in addition the expected flux of thermal X-rays is estimated here. This is only possible in a very approximate way, even if we disregard the ejecta emission with the argument that the ejected mass in the present phase is small compared to the swept-up mass.…”

A young supernova remnant illuminating nearby molecular clouds with cosmic rays

“…This density profile was used by Berezhko & Völk (2006) and Berezhko et al (2009) for the case of RX J1713.7-3946 and Vela Jr., with n(r) = n b + (r/R b ) 3(σ sh −1) n sh , where n sh = σ sh n ICM is the maximum density of the shell at the outer boundary of the shell. In our work, we set σ sh = 5.…”

“…Or, the known TeV-emitting shells no longer confine previously accelerated PeV (hadronic) particles; those particles would have escaped at earlier times of the SNR evolution and are at present already diffusing into the environment of the SNR. The latter hypothesis has been discussed in several works as a possibility to lower the high energy cutoff of TeV spectra of young SNRs in hadronically dominated TeV emission scenarios (e.g., Berezhko et al 2003;Malkov et al 2005;Berezhko et al 2009). …”