Radio, visible-light, and X-ray observations have revealed that ASKAP J1745 is a binary system in which a white dwarf is accreting material from a companion star. Researchers hope the system will serve as a sort of "Rosetta Stone" for deciphering long-period radio transients.
A pair of interacting stars may help astronomers decipher the origin of a rare type of recurring radio burst.
ASKAP J1745, a new source of periodic radio bursts, likely originates from two stars orbiting each other in close orbit. One is a white dwarf – a dense remnant of a star – that is absorbing material from its companion star.
In recent years, astronomers have been trying to explain radio flashes known as "Long-period radio transients". In contrast topulsars And for other radio sources, which emit signals at a rapid rate, these sources produce bursts that repeat at intervals of minutes and even hours.
The signals were first discovered by chance, when radio telescopes scanned large areas of the sky. So far, only about a dozen such unusual sources have been identified, and the origin of most of them is still unknown.
In the new study, researchers report for the first time radio bursts andX-rays Which repeat in synchronization with the entire orbit of the two stars in a binary system.
ASKAP J1745 is notable because astronomers have been able to identify the type of system producing the signals. In 10 of the 12 known long-period radio transients, the precise astronomical source has not yet been identified. The system is also important because it was observed using several telescopes, which are sensitive to different types of electromagnetic radiation.
The famous Rosetta Stone, which contained the same message in three different scripts, allowed researchers to decipher ancient Egyptian cuneiform. Similarly, the wealth of information gathered about ASKAP J1745 may help astronomers solve the mystery of long-period radio transients.
What do long-period radio transients look like?
Long-period radio transients are objects in space that produce bright, recurring bursts of radio radiation. Very little is known about the origin of most of these objects.
Many of them were discovered near the dusty region at the center of the Milky Way. Interstellar dust makes it difficult to detect the objects with telescopes operating in visible light, so astronomers have difficulty discovering which stars or systems are hiding where the radio signals are coming from.
Although only about a dozen such sources have been discovered so far, they appear to be quite distinct. Their radio bursts repeat at intervals ranging from minutes to hours.
Some sources have been producing regular pulses for more than 30 years. Others stop transmitting for days, while a few sources have gone completely silent and no further radio signals have been observed from them since.
Where do the signals come from?
Initially, astronomers thought that long-period radio transients were Neutron stars Which rotate very slowly – that is, extremely slow pulsars.
Neutron stars are the dense remnants left over from the supernova explosions of massive stars. Many of them spin rapidly and emit beams of radio wavesWhen one of the beams passes over the Earth, the telescopes pick up a periodic pulse.
The first long-period transients discovered produced signals at intervals of about 20 minutes. This is a much longer period than the period of a typical pulsar, which usually rotates in seconds and sometimes even milliseconds.
There is also a theoretical problem with this explanation. When a pulsar slows its rotation sufficiently, it should stop emitting radio waves. Therefore, radio bursts from neutron stars that rotate so slowly would not be expected to be detected.
Astronomers therefore began to examine other explanations, including White dwarfsA white dwarf is the remnant of the core of a star whose initial mass was too low to become a neutron star. After the star sheds its outer layers, a dense, hot core remains that gradually cools.
In recent years, several long-period radio transients have been discovered inBinary systems, in which a white dwarf and a low-mass red dwarf star orbit each other in close orbit.
The discovery of ASKAP J1745
ASKAP J1745 is a long-period radio transient discovered by the ASKAP radio telescope in Western Australia. The telescope is operated by CSIRO, Australia's national science agency.
This is the first source of this type that researchers have been able to identify as a system known as a "cataclysmic variable."
Cataclysmic variables They are systems consisting of two stars, one of which is a white dwarf. The stars orbit each other at a distance small enough to allow interaction between them.
When the distance is particularly small, the gravity of the white dwarf pulls in material from the companion star. The material flows toward the white dwarf and accumulates around it in a process called accretion. For this reason, these systems are also called accreted white dwarf binaries.
Another long-period radio transient was recently discovered to also produce X-ray bursts, which recurred with the same regularity as the radio bursts. However, the origin of the bursts and the reason for their common timing remained unclear.
In the new study, the researchers combined observations from telescopes operating in the radio, visible light and X-ray ranges for the first time. The observations showed that ASKAP J1745 produces radio and X-ray bursts every time the two stars complete an orbit around each other.
The origin of X-rays
In systems where two stars orbit each other rapidly, the X-ray radiation likely arises from material heating up as it flows from the companion star toward the white dwarf.
As the material falls into the strong gravitational field of the white dwarf, it is accelerated and reaches very high temperatures. The hot material emits high-energy radiation, including X-rays.
The origin of the bright radio bursts was harder to explain, but knowing that they were a binary system in which a white dwarf was accreting matter gave the researchers an important clue.
Pulsed radio radiation of the type observed is typically produced when high-energy particles interact with strong magnetic fields.
ASKAP J1745 has the necessary combination: two stars with strong magnetic fields and a stream of charged particles moving from the companion star to the white dwarf. According to the researchers, the strength of the magnetic fields in the system may be thousands of times greater than the magnetic field in an MRI machine.
The periodic motion of the stars and the changing flow of matter between them may explain why the radio and X-ray bursts repeat according to the orbital cycle.
The "Rosetta Stone" of radio listeners
ASKAP J1745 is unique in the amount of information collected about it and the range of wavelengths it was observed in. It is the first long-period radio transient to show clear signs of material absorption across many parts of the electromagnetic spectrum – from radio waves, through visible light, to X-rays.
The flow of charged material from the companion star to the white dwarf may be a key component in generating the radio bursts measured in such systems.
Researchers hope that ASKAP J1745 will play a role similar to that of the Rosetta Stone in deciphering the cuneiform script. Understanding the relationship between stellar orbits, material absorption, X-rays, and radio bursts could help interpret signals from other long-period transients that are not available from observations at other wavelengths.
Studying the mechanism that produces long-period radio bursts also provides astronomers with a natural laboratory for studying physics under extreme conditions. Among other things, such systems can be used to study plasma flows, the movement of charged particles, and magnetic fields at intensities that cannot be reproduced in laboratories on Earth.
The study, titled “Periodic radio and X-ray emission from an accreting white dwarf binary,” was published on June 1, 2026, in the journal Nature Astronomy. DOI: 10.1038 / s41550-026-02882-x
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