MeerKAT-based multi-wavelength study of supernova remnant G7.7-3.7 (SN386?)

Abstract

We investigated the structural characteristics of G7.7-3.7 at a higher resolution of 1284 MHz. MeerKAT observations revealed that G7.7-3.7 had an asymmetric spherical structure with filamentary features and various blowouts. The western boundary showed a strong bright blowout, while the southern perimeter showcased extended bright filaments with feather-like structures, which seemed disconnected from the western blowout. Moreover, the eastern region exhibited a blowout centered around a bright point source, with faint, elongated filaments extending north-west. These filaments connected the eastern point source to the western blowout, creating a uniform outward progression. Spectral index analysis indicated a steep spectrum ($\alpha$ ranged $\sim$ 0 to $\sim$ −3), suggesting a combination of synchrotron and a few traces of thermal emissions concentrated at the edges of bright blowouts. Analysis of MeerKAT and VLA data revealed that G7.7-3.7 had expanded by 9 ± 0.45 arcsec over a period of 31.907 years, corresponding to an expansion rate of 0.282 ± 0.014 arcsec yr⁻¹. This expansion indicated a shock speed of 5883 ± 294 km s⁻¹ and an age of 1636 ± 115 years. This age fits with the supernova explosion event of 386 CE and the MeerKAT observed data in 2023. The multi-wavelength investigation unveiled a distinctive structure within the southern radio blowout, encompassing a bright radio blowout, a prominent X-ray arc, and two faint optical filaments aligned with the X-ray bright arc. We attributed the bright radio blowouts to inhomogeneous mass outflow from shock-accelerated particles and the weakening of magnetic fields along its perimeter. Traces of thermal emissions, especially along the edges of blowouts, were likely due to shock-heated gas, which intensified in the southern region amid high-density Interstellar Medium (ISM). Therefore, these results supported a scenario in which the progenitor supernova of G7.7-3.7 exploded within ISM of varying density, generating the observed X-ray emissions and faint optical filaments. Our findings provided valuable insights into the dynamics and evolution of supernova remnants.