Breakthrough collaboration between multiple telescopes reveals most unusual long-period radio transient ever found
Astronomers have made a groundbreaking discovery using some of the world’s most advanced radio telescopes. Researchers, led by Fengqiu Adam Dong, a Jansky Fellow at the NSF Green Bank Observatory (NSF GBO), have identified an exceptionally unusual cosmic object known as a Long Period Radio Transient (LPT), named CHIME J1634+44. This object stands out as one of the most polarized LPTs ever discovered, and it is the only one observed to be spinning up (meaning its rotation is speeding up) a phenomenon never seen before in this class of astronomical objects.
The telescopes used in this discovery include:
- U.S. National Science Foundation Green Bank Telescope (NSF GBT)
- NSF Very Large Array (NSF VLA)
- Canadian Hydrogen Intensity Mapping Experiment (CHIME) Fast Radio Burst and Pulsar Project
- NASA’s Neil Gehrels Swift Observatory (Swift)
LPTs are a newly discovered type of radio-emitting object with extremely long rotation periods, sometimes lasting minutes to hours. CHIME J1634+44’s unique properties, such as a mysterious decrease in spin period and unusual polarization, challenge the current scientific understanding and raise new questions about how these objects work and what they can teach us about the Universe.
“You could call CHIME J1634+44 a ‘unicorn’, even among other LPTs,” said Dong, noting this LPT’s particularly unusual traits. Despite hundreds of detections across multiple observatories, including those listed above, and additional observations by the LOw Frequency ARray (LOFAR) in the Netherlands, the timing of the repeating radio bursts from CHIME J1634+44 is unclear. “The bursts seem to repeat either every 14 minutes, or 841 seconds—but there is a distinct secondary period of 4206 seconds, or 70 minutes, which is exactly five times longer. We think both are real, and this is likely a system with something orbiting a neutron star,” explained Dong.
Normally, objects like neutron stars or white dwarfs slow down over time because they lose energy, so their spin period gets longer. But for CHIME J1634+44, the period is actually getting shorter—meaning it’s spinning up, not slowing down. The only way to make the timing of the bursts fit together is to assume this spin-up is real, but that doesn’t make sense for a lone star. Therefore, researchers believe that CHIME J1634+44 might actually be two stars orbiting each other very closely. If the orbit of this binary system is shrinking, it could be because they are losing energy, by emitting gravitational waves or interacting with each other, which could make it look like the period is getting shorter. This kind of shrinking orbit has been seen in other close pairs of white dwarfs. The radio bursts from CHIME J1634+44 are 100% circularly polarized, which means the radio waves twist in a perfect spiral as they travel—which is extremely rare. No known neutron star or white dwarf has ever been seen to do this for every burst. This suggests that the way these radio waves are being produced is different from what we see in all other known objects.
The unparalleled collection of telescopes used in this research allowed scientists to detect and study the object’s unusual signals in detail. CHIME’s wide field of view and daily sky scans detected the transient’s periodic bursts and monitored its spin evolution. The NSF VLA, supported by realfast (a system for real-time fast transient searches at the NSF VLA via interferometric imaging), provided high-frequency follow-up observations to mitigate interstellar medium distortions and refine localization. The NSF GBT contributed sensitive, high-resolution timing data to analyze polarization and spin-up behavior, enhancing precision for gravitational wave studies. Swift searched for X-ray counterparts, and its multi-wavelength capabilities allowed the researchers to probe for high-energy signals that complemented the radio observations from the NSF GBT, NSF VLA and CHIME.
“The discovery of CHIME J1634+44 expands the known population of LPTs and challenges existing models of neutron stars and white dwarfs, suggesting there may be many more such objects awaiting discovery,” adds Dong. This finding opens new avenues in radio astronomy and brings us a step closer to unraveling the mysteries of these enigmatic cosmic beacons.
About GBO
The Green Bank Observatory (GBO), part of the National Radio Astronomy Observatory (NRAO), are major facilities of the U.S. National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
About CHIME
The CHIME project is co-led by the University of British Columbia, McGill University, University of Toronto, and the Dominion Radio Astrophysical Observatory with collaborating institutions across North America.