Twenty-Year Radio Mystery Solved: Astronomers Pin Long-Period Radio Bursts on a 'Vampire' White Dwarf Feeding on Its Companion
Summary: First detected in 2005, long-period radio transients (LPTs) — a rare class of celestial radio emission lasting minutes to over an hour, far longer than typical pulsar bursts — have puzzled astronomers for two decades. Roughly a dozen are now known, with the leading explanation being highly magnetic neutron stars called magnetars. New observations from the Australian SKA Pathfinder (ASKAP) array, led by University of Sydney PhD student Kovi Rose, show that at least one LPT — catalogued as ASKAP J1745-5051 — comes from a symbiotic binary: a white dwarf with a mass comparable to the Sun but a diameter no larger than Earth's, accreting material from a red dwarf companion about a tenth of the Sun's mass.
What sets ASKAP J1745-5051 apart is that it produces both long-period radio bursts and X-ray flares — a rare combination among the dozen known LPTs. "Long-period radio transients have puzzled astronomers for years," Rose said in the team's statement. "Now we've been able to show that the source for one of these transients comes from a white dwarf actively pulling material from a companion star."
The binary completes an orbit every 1.4 hours, on a strongly elliptical path. As matter spirals from the red dwarf toward the white dwarf, friction heats it to hundreds of thousands — even millions — of degrees, generating the X-ray emission. The radio emission, by contrast, is produced when the two stars' magnetic fields clash at close approach, stripping charged particles from their surfaces. The team noted that the radio and X-ray signals do not peak at the same moment, indicating they originate in different regions of the system.
The result does not, on its own, explain all long-period radio transients: only one other known LPT also produces X-rays, leaving room for other origins among the rest. Rose likened ASKAP J1745-5051 to a "stellar Rosetta Stone" — a system that could help astronomers distinguish between magnetar-driven and white-dwarf-driven LPTs in future surveys.
Sources (original pages)
- Scientists locate source of mysterious radio signals after 20 year search: A vampire star and its victim — Space.com (by Keith Cooper, June 2, 2026)