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

¹ DESY, 15738 Zeuthen, Germany
e-mail: robert.brose@mail.de
² Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
³ Centre for Space Research, North-West University, 2520 Potcheftroom, South Africa
⁴ Astronomical Observatory of Ivan Franko National University of L’viv, vul. Kyryla i Methodia, 8, L’viv 79005, Ukraine
⁵ Western Sydney University, Locked Bag 1797, Penrith NSW 2751, Australia
⁶ Sorbonne University, 4 place Jussieu, 75005 Paris, France
⁷ Université de Versailles Saint-Quentin-en-Yvelines, 45 rue des États-Unis, 78000 Versailles, France

Received: 15 October 2018
Accepted: 29 May 2019

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 yr and inferred shock speed of ≈14 000 km s⁻¹ 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 evaluate the prospects of its detection with future gamma-ray experiments.

Methods. We performed spherical symmetric 1D simulations with the RATPaC code, in which we simultaneously solved 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 were 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 nonthermal 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. 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.