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

Abstract

Aims.A nonlinear kinetic theory of cosmic ray (CR) acceleration in supernova remnants (SNRs) is employed to investigate the properties of SNR RX J1713.7-3946. Methods. Observations of the nonthermal radio and X-ray emission spectra, as well as the HESS measurements of the very high energy γ-ray emission, are used to constrain the astronomical and CR acceleration parameters of the system. It is argued that RX J1713.7-3946 is a core collapse supernova (SN) of type II/Ib with a massive progenitor, and it has an age of ≈1600 yr and is at a distance of ≈1 kpc. It is also assumed that the CR injection/acceleration takes place uniformly across the shock surface for this kind of core collapse SNR. Results. The theory gives a consistent description for all the existing observational data, including the nondetection of thermal X-rays and the spatial correlation of the X-ray and γ-ray emission in the remnant. Specifically, it is shown that an efficient production of nuclear CRs, leading to strong shock modification and a strong downstream magnetic field B d ≈ 140 μG can reproduce in detail the observed synchrotron emission from radio to X-ray frequencies, together with the γ-ray spectral characteristics as observed by the HESS telescopes. Conclusions. The calculations are consistent with RX J1713.7-3946 being an efficient source of nuclear CRs.

The Role of Diffusive Shock Acceleration on Nonequilibrium Ionization in Supernova Remnant Shocks. Ii. Emitted Spectra

“…However, Ellison et al (2010) argue that if the TeV γ -ray emission were hadronic in origin, thermal X-ray emission would be detected, though the model used there is for a constant ambient medium density of 0.2 cm −3 , for the hadronic scenario. In the model developed by Berezhko & Völk (2010), the SNR blast wave has been expanding through a low-density (n H ≈ 0.0008 cm −3 ) bubble and has recently encountered the bubble wall, with n H = 0.25 cm −3 at present. From their model, we estimate that the shock began encountering the bubble wall ∼800 years ago, as determined by the curve for N g in the top panel of their Figure 1 (Berezhko & Völk 2010).…”

“…From their model, we estimate that the shock began encountering the bubble wall ∼800 years ago, as determined by the curve for N g in the top panel of their Figure 1 (Berezhko & Völk 2010). They assume that the thermal X-ray emission as determined for the Sedov solution by Hamilton et al (1983) is reduced by an amount equivalent to the ratio of the bubble emission measure to the Sedov emission measure, here equal to 0.46 (Berezhko & Völk 2010). Additionally, they assume a value of η = 8 × 10 49 , where η = n 2 E SN (Hamilton et al 1983).…”

“…Their chosen value of η corresponds to an explosion energy of 1.3 × 10 51 erg and an ambient medium density of 0.25 cm −3 . They use the value of η and an assumed electron temperature of 1 keV to estimate the thermal X-ray emission from the recently shocked bubble wall, and they find that, at 1 keV, the thermal X-ray emission is approximately half the nonthermal flux (Berezhko & Völk 2010).…”

“…We find that the results differ, mainly at lower energies. Finally in Section 4, we discuss the recent result by Berezhko & Völk (2010) and show that the absence of thermal X-ray emission does not naturally lead to the interpretation that the TeV gamma-ray emission is hadronic in origin. We argue that if the blast wave has only recently hit the circumstellar shell, then the shocked gas, though at X-ray-emitting temperatures, will be underionized.…”

The structure of TeV-bright shell-type supernova remnants

“…The nonthermal emission of these remnants has a welldefined shell structure and there is evidence that the relative mean thickness of the emitting shell varies from remnant to remnant (Aharonian et al 2006. Previously 1D modeling of particle acceleration in SNRs has been used to study the radial brightness profile in the hadronic scenario (Berezhko & Völk 2010). A detailed study of the source structure with magnetohydrodynamic (MHD) simulations has not been carried out.…”