Identify the physical origin of the latest radio spectrum

Identify the physical origin of the latest radio spectrum of AT 2019avd by determining whether its late-time emission is produced by a forward shock that becomes increasingly important as the swept-up circumnuclear-medium mass grows or by a bow shock generated when the outflow encounters an additional dense cloud at larger radius.

Background

The outflow–cloud simulations reproduce most of the observed radio spectra of AT 2019avd, but show their largest discrepancy at the final epoch. The paper proposes two possible additional-emission mechanisms: a forward shock emerging as the swept-up circumnuclear-medium mass approaches the ejecta mass, or a second bow shock produced by interaction with another cloud. The authors do not resolve which mechanism is responsible and suggest that continued radio monitoring and very-long-baseline interferometry could help distinguish them.