What are the long-period radio transients?
In plain words
Radio telescopes have found, mostly since 2022, sources that pulse once every few minutes to hours, far slower than any known pulsar should still emit radio waves.
Precise statement
Long-period radio transients (periods from $\sim 1\,\mathrm{min}$ to several hours, for example GCRT J1745-3009 at $77\,\mathrm{min}$, GLEAM-X J1627-52 at $18\,\mathrm{min}$ and GPM J1839-10 at $21\,\mathrm{min}$) emit coherent, highly polarized pulses below conventional pulsar death lines. Two, ILT J1101+5521 and GLEAM-X J0704-37, are white dwarf-M dwarf binaries. Determine whether all are white-dwarf systems or whether some are ultra-long-period magnetars, and identify the emission mechanism. Answer: a classification per source with a mechanism consistent with spin-down or binary energy budgets.
What would settle it
Optical and X-ray identification of counterparts and measured period derivatives for the isolated sources.
Status in the literature
Unverified note
2024-2025: ILT J1101+5521 (2.1 h) and GLEAM-X J0704-37 (2.9 h) were shown to be white dwarf-M dwarf binaries, while ASKAP J1832-0911 (44 min) showed X-ray pulses at the radio period; the nature of sources without optical companions is debated.