Astronomers have pinpointed the source of a mysterious repeating radio signal emanating from within the Milky Way galaxy: a binary system consisting of a white dwarf star and a red dwarf star. The signal, known as GPM J1839-10, has puzzled researchers for a decade, emitting bright radio pulses with an unusually long period of 21 minutes – the longest observed of its kind.
The breakthrough, detailed in a paper published in Nature Astronomy, involved coordinated observations from three radio telescopes across the globe: MeerKAT in South Africa, ASKAP in Australia and the VLA in the United States. This sequential approach allowed for uninterrupted tracking of the signal as the Earth rotated, providing the precision needed to identify its origin.
A Stellar Dance Generating Radio Waves
The research team discovered that the radio pulses arrive in groups of four or five, appearing in pairs separated by approximately two hours, with the entire pattern repeating every nine hours. This nine-hour cycle corresponds to the orbital period of the binary system. The system’s behavior strongly suggests a white dwarf – the dense remnant of a Sun-like star – is spinning and its magnetic axis intersects with the stellar wind emanating from its red dwarf companion. This interaction generates the observed radio emissions.
“In each orbit, the visible pulses appear twice, with four to five individual bursts,” explains the research, confirming a complex emission pattern tied directly to the orbital mechanics of the two stars.
Long-Period Transients and Binary Systems
The discovery adds to a growing body of evidence linking long-period transients (LPTs) – radio signals with unusually long repeating periods – to binary systems. Around a dozen such LPTs have been identified over the past four years, all originating from galactic objects of unknown origin. This latest finding strongly suggests that many, if not most, LPTs are produced by similar mechanisms: plasma and magnetic field interactions within extreme binary environments.
Previously, long radio bursts were primarily attributed to neutron stars, incredibly dense objects formed after supernova explosions. However, the identification of GPM J1839-10 as a white dwarf-red dwarf binary expands the known sources of these signals, challenging existing assumptions about their origins.
How the Signal Was Tracked
The precision required to pinpoint the source of GPM J1839-10 necessitated a unique observational strategy. The team leveraged the complementary capabilities of the three radio telescopes, effectively creating a continuous observation window. As the Earth rotated, each telescope took over tracking the signal, ensuring no data was lost. This coordinated effort was crucial in establishing the signal’s location and characterizing its behavior.
The analysis of the signal’s structure revealed the grouping of pulses, providing a key clue to the underlying mechanism. Modeling based on white dwarf pulsar geometry – considering the rotation and magnetic field alignment of the white dwarf – successfully reproduced the observed intermittent emission and double-pulse structure.
Implications for Understanding Stellar Evolution
This research provides a framework for studying the growing population of LPTs and related white dwarf binaries. It suggests that radio emissions from such systems may be more common and varied than previously recognized. Understanding these emissions can offer valuable insights into the evolution of exotic binary systems and the complex interactions between stars in close proximity.
The discovery also opens new avenues for exploring the magnetic fields of white dwarfs and the processes that govern their interactions with companion stars. Further research will focus on identifying additional LPTs and characterizing their properties to refine our understanding of these fascinating celestial phenomena.
The team hopes this discovery will motivate radio astronomers to localize new classes of sources that might arise from neutron star or magnetar binaries, furthering our understanding of the universe’s most energetic and mysterious objects.
