CHIME J1634+44: Sample of a detection made with the CHIME/Pulsar instrument.

An international team of astronomers report the discovery of a long-period radio transient, which is unusually circularly polarized and showcases an accelerating spin period. The finding of the new transient, designated CHIME J1634+44, was detailed in a paper published July 7 on the pre-print server arXiv.

The term long-period radio transients (LPTs) refers to a new class of periodic radio emitters, with ultralong rotation periods (ranging from minutes to hours) and strong magnetic fields. Although some observations have suggested that these transients may originate from rotating neutron stars with extremely strong magnetic fields (magnetars) or magnetic white dwarfs, their true nature is still elusive.

Now, a group of astronomers led by Fengqiu Adam Dong of the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, has identified a new object of this emerging class of transients. The discovery was made as part of the Canadian Hydrogen Intensity Mapping Experiment (CHIME)/Fast Radio Burst (FRB)/Pulsar survey for Galactic pulsars.

"CHIME J1634+44 was discovered in the CHIME/FRB single-pulse pulsar survey, where we are using the CHIME/FRB trigger criteria for all sources with a dispersion measure (DM) low enough to be considered inside the Milky Way galaxy according to both the NE2001 and the YMW16 DM models," the researchers wrote in the paper.

CHIME J1634+44 was first identified during its first burst in October 2022 and was monitored since then, which resulted in the detection of further reactivation periods in February and November 2023. In total, 89 unique bursts were detected over a period of approximately 4.5 years.

According to the paper, CHIME J1634+44 has a pulse period of 841 seconds and showcases a secondary period of approximately 4,206 seconds. This secondary period is possibly associated with binary activity.

The observations found that CHIME J1634+44 emits fully circularly polarized radio bursts and has an accelerating spin period as it showcases a significantly negative period derivative of about -9.03 seconds/second. The astronomers note that this makes CHIME J1634+44 the first known LPT that is circularly polarized and exhibits a significant spin-up.

The authors of the paper suppose that the spin up of CHIME J1634+44 is likely generated by accretion of material from a companion or may be caused by gravitational wave radiation. However, further observations of the transient are required to confirm this.

Summing up the results, the researchers underline the unique properties of CHIME J1634+44 that make it an excellent place to look for answers regarding the true nature of LPTs.

"CHIME J1634+44 will serve as an important test bed for LPT emission theories and is unique among the array of known transient source emitters," the scientists conclude.

Written for you by our author Tomasz Nowakowski, edited by Sadie Harley, and fact-checked and reviewed by Andrew Zinin—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

More information: Fengqiu Adam Dong et al, CHIME/FRB Discovery of an Unusual Circularly Polarized Long-Period Radio Transient with an Accelerating Spin Period, arXiv (2025). DOI: 10.48550/arxiv.2507.05139

Journal information: arXiv