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Abstract

Core-collapse (CC) supernova remnants (SNRs) are the nebular leftovers of defunct massive stars that died during a supernova explosion, mostly while undergoing the red supergiant phase of their evolution. The morphology and emission properties of those remnants are a function of the distribution of circumstellar material at the moment of the supernova, as well as the intrinsic properties of the explosion and those of the ambient medium. By means of 2.5-dimensional (2.5D) numerical magneto-hydrodynamic (MHD) simulations, we modelled the long-term evolution of SNRs generated by runaway rotating massive stars moving into a magnetised interstellar medium (ISM). Radiative transfer calculations reveal that the projected non-thermal emission of SNRs decreases over time, namely: older remnants are fainter than younger ones. Older (80 kyr) SNRs whose progenitors were moving with a space velocity corresponding to a Mach number of M = 1 (v_⋆ = 20 km s⁻¹) in the Galactic plane of the interstellar medium (n_ISM = 1 cm⁻³) are brighter in synchrotron than when moving with a Mach number of M = 2 (v_⋆ = 40 km s⁻¹). We show that runaway red supergiant progenitors first induce an asymmetric non-thermal 1.4 GHz barrel-like synchrotron SNRs (at the age of about 8 kyr), before further evolving to adopt a Cygnus-loop-like shape (at about 80 kyr). It is conjectured that a significative fraction of SNRs are currently in this bilateral-to-Cygnus loop evolutionary sequence. Therefore, this population should be taken into account with repect to interpreting the data as part of the forthcoming Cherenkov Telescope Array (CTA) observatory.