Nonthermal emission from the reverse shock of the youngest Galactic supernova remnant G1.9+0.3

Abstract

Context. The youngest Galactic supernova remnant G1.9+0.3 is an interesting target for next generation gamma-ray observatories. So far, the remnant is only detected in the radio and the X-ray bands, but its young age of ≈ 100 yrs and inferred shock speed of ≈ 14, 000 km/s could make it an efficient particle accelerator. Aims. We aim to model the observed radio and X-ray spectra together with the morphology of the remnant. At the same time, we aim to estimate the gamma-ray flux from the source and evaluated the prospects of its detection with future gamma-ray experiments. Methods. We performed spherical symmetric 1-D simulations with the RATPaC code, in which we simultaneously solve the transport equation for cosmic rays, the transport equation for magnetic turbulence, and the hydro-dynamical equations for the gas flow. Separately computed distributions of the particles accelerated at the forward and the reverse shock are then used to calculate the spectra of synchrotron, inverse Compton, and pion-decay radiation from the source. Results. The emission from G1.9+0.3 can be self-consistently explained within the test-particle limit. We find that the X-ray flux is dominated by emission from the forward shock while most of the radio emission originates near the reverse shock, which makes G1.9+0.3 the first remnant with non-thermal radiation detected from the reverse shock. The flux of very-high-energy gamma-ray emission from G1.9+0.3 is expected to be close to the sensitivity threshold of the Cherenkov Telescope Array, CTA. The limited time available to grow large-scale turbulence limits the maximum energy of particles to values below 100 TeV, hence G1.9+0.3 is not a PeVatron.

Time-dependent Treatment of Cosmic-ray Spectral Steepening Due to Turbulence Driving

“…As cosmic-ray ions typically carry more energy density than do the electrons, they would provide most of the amplified field, and it is questionable whether any estimate of spectral steepening can be directly applied to electrons and hence to radio synchrotron spectra. Besides, the youngest known SNR in the Galaxy, G1.9+0.3, has a very fast forward shock (Reynolds et al 2008), but the radio emission most likely comes from the reverse shock whose speed is considerably lower (Brose et al 2019).…”

Modeling non-thermal emission from SN 1987A

“…We solve the transport equation for protons in 1D using the RATPaC code as described in [2,[28][29][30] taking into account only a forward shock and ignoring the reverse shock. Resulting proton spectra at different epochs are then used to calculate the Pion-decay emission from the remnant.…”

The impact of the circumstellar magnetic field of progenitor stars on the resulting gamma-ray spectrum from supernova remnants

“…The impact of the circumstellar magnetic field on the gamma-ray emission from SNRs Iurii Sushch R, pc We solve the transport equation for electrons in 1D using the RATPaC code as described in [2,3,4,5] taking into account only a forward shock and ignoring a reverse shock. Resulting electron spectra at different moments of time are then used to simulate inverse Compton emission from the remnant.…”

“…In this scenario synchrotron losses might cause a cooling break in the spectrum appearing at quite low GeV energies resembling a characteristic pion-decay feature. In this work we aim to study such a possibility through the simulation of the SNR evolution and particle acceleration in the circumstellar environment of the stellar wind bubble of the progenitor star using the RATPaC (Radiation Acceleration Transport Parallel Code) code [2,3,4,5].…”