An international team of astronomers has unveiled the discovery of a new long-period radio transient, designated as ASKAP J144834−685644 (commonly referred to as ASKAP J1448−6856). This important finding adds to the limited collection of known sources within this emerging class of celestial phenomena. The details of the discovery were released in a paper published on July 17, 2025, on the arXiv preprint server.
Long-period radio transients (LPTs) are a novel category of periodic radio emitters characterized by ultralong rotation periods, which can range from minutes to hours, and possess strong magnetic fields. While some observations indicate that these transients may originate from rotating neutron stars known as magnetars or magnetic white dwarfs, their precise nature remains a mystery to astronomers.
The Australian Square Kilometre Array Pathfinder (ASKAP), a 36-dish radio interferometer located in Australia, operates within a frequency range of 700 to 1,800 MHz. One of its main scientific objectives is to characterize the radio transient sky by detecting and monitoring transient and variable sources. A group of astronomers led by Akash Anumarlapudi from the University of Wisconsin–Milwaukee made the latest detection using ASKAP.
In their search for circularly polarized sources, the team identified ASKAP J1448−6856, which exhibits highly variable emissions, both linearly and circularly polarized. The researchers stated, “We report the discovery of a new LPT, ASKAP J1448−6856. Discovered as a 1.5-hour periodic radio source, ASKAP J1448−6856 shows a steep spectrum, elliptical polarization, and periodic narrowband emission that declines at frequencies above 1.5 GHz.”
The newfound transient displays emission characterized by a harmonic frequency structure and polarized bursts. Its emission is elliptically polarized, with the polarization fraction varying between 35% and 100% across different observations. Notably, ASKAP J1448−6856 is detected across multiple wavelengths, from X-rays to radio, and exhibits variability in optical bands. This positions it among a select group of LPTs identified from X-ray to radio wavelengths.
According to the research paper, multiwavelength modeling of the spectral energy distribution (SED) of ASKAP J1448−6856, alongside its radio properties, suggests it may be a near-edge-on magnetic white dwarf (MWD) binary system with a magnetic field strength exceeding 1,000 Gauss. Nonetheless, the study’s authors caution against ruling out other possibilities, including that ASKAP J1448−6856 could be an isolated white dwarf pulsar or a transitional millisecond pulsar-like system.
The discovery of ASKAP J1448−6856 is significant for advancing the understanding of the LPT population. The researchers concluded, “Combining ASKAP J1448−6856 with the growing number of long-period radio transients adds to the variety of multi-wavelength behavior and will help deepen our understanding of this emerging population (or, indeed, populations).”
This finding not only enriches the catalog of known radio transients but also contributes to the broader scientific discourse surrounding the nature of these intriguing astronomical phenomena.
