The Decline and Fall of ROME. V. A Preliminary Search for Star-disrupted Planet Interactions and Coronal Activity at 5 GHz among White Dwarfs within 25 pc

Abstract The recent discovery of planetesimals orbiting white dwarfs has renewed interest in the final chapters of the evolution of planetary systems. Although observational and theoretical studies have examined the dynamical evolution of these systems, studies of their magnetic star–planet interactions, as powered by unipolar induction, have thus far only been assessed theoretically. This fifth paper of the Radio Observations of Magnetized Exoplanets series presents the results of a targeted minisurvey of nine white dwarfs within 25 pc without known stellar mass companions in search of radio emissions generated by magnetic interactions between white dwarfs and their planetary remnants. This ∼5 GHz Arecibo radio telescope survey achieved mJy-level sensitivity over <1 s integration times. Although no exoplanet-induced stellar radio flares were detected, this is the first survey to search for magnetic star–planet interactions between white dwarfs and planetary companions, cores, or disrupted planetesimals. It is also the most extensive and sensitive radio survey for intrinsic coronal emissions from apparently isolated white dwarfs. The study of radio emissions from white dwarf systems may present a new means to detect and measure DC and DQ magnetic fields, search for white dwarf coronae, characterize the density and spatial distribution of white dwarf magnetospheric plasma, characterize the dynamical and electrical properties of planetary cores, and offer new constraints on the modeling of double-degenerate merger events.