Sensitive Constraints on Coherent Radio Emission from Five Isolated White Dwarfs

TL;DR

This study conducted the most sensitive search to date for radio emissions from five isolated white dwarfs using major radio telescopes, finding no signals and setting strict constraints on the existence of WD pulsars.

Contribution

It provides the first comprehensive, highly sensitive observational constraints on radio emissions from isolated, magnetized white dwarfs, highlighting the importance of binary interactions for detectable emission.

Findings

No pulsed or continuum radio emission detected from the five white dwarfs.

Results suggest that isolated WD pulsars are either intrinsically weak, narrowly beamed, or require binary interactions.

Future telescopes like SKA are needed to detect fainter or sporadic emissions.

Abstract

Coherent, periodic radio emission from pulsars has been widely interpreted as evidence of neutron stars as strongly magnetized compact objects. In recent years, radio pulses have also been detected from white dwarfs (WDs) in tight binary systems, raising the question of whether isolated WDs could similarly host pulsar-like emission. We conducted the most sensitive search to date for coherent radio signals from five isolated, rapidly rotating, and magnetized WDs, using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), the Green Bank Telescope (GBT), and the Australia Telescope Compact Array (ATCA). No pulsed or continuum radio emission was detected down to $\mu$Jy levels. These non-detections place the most stringent observational constraints yet on the existence of isolated WD pulsars. Our results suggest that either such emission is intrinsically weak, narrowly beamed, or requires binary-induced magnetospheric interactions absent in solitary systems. Comparison with the known radio-emitting WDs highlights the critical role of companion interaction in enabling detectable emission. This work expands on prior surveys by targeting sources with the most favorable physical conditions for WD pulsar-like activity and employing highly sensitive, targeted observations. Future observations with next-generation facilities such as the SKA will be essential to explore fainter or sporadic emission from massive, magnetic WDs and to investigate their potential as compact radio transients further.