A pair of stars orbiting each other is the source of a newly detected repeating radio burst called ASKAP J1745. In recent years, astronomers have studied mysterious radio signals known as long-period transients due to their slow repetition rates. These were first found accidentally during wide sky surveys. Only about a dozen such sources are known, and their exact nature remains unclear. A new study in Nature Astronomy reports the first detection of both radio and X-ray bursts repeating with each orbit. ASKAP J1745 stands out because its nature has been identified, unlike most other long-period transients. Multiple telescopes observing different wavelengths provided key data. Like the Rosetta stone that aided translation of ancient scripts, these combined observations should help explain other similar sources. Long-period transients emit bright, repeating radio bursts on timescales from minutes to hours. Many lie near the dusty galactic center, making optical observations difficult. They vary in behavior, with some pulsing regularly for decades and others turning off temporarily or permanently. Astronomers once attributed them to slowly spinning neutron stars known as pulsars. However, their periods are far longer than typical pulsars, and such slow rotation should not produce radio emission. Alternative explanations involving white dwarfs in binary systems have gained support. ASKAP J1745 was found using the ASKAP radio telescope and identified as a cataclysmic variable, or accreting white dwarf binary. In these systems, a white dwarf pulls material from a companion star. Combined radio, X-ray, and optical data show that bursts occur with each orbit. X-ray emission arises from heated material accreting onto the white dwarf, while radio bursts result from energetic particles interacting with strong magnetic fields.
