A highly magnetized long-period radio transient exhibiting unusual emission features

Long-period radio transients are a new class of astrophysical objects that
exhibit periodic radio emission on timescales of tens of minutes. Their
true nature remains unknown; possibilities include magnetic white dwarfs,
binary systems, or long-period magnetars; the latter class are predicted
to produce fast radio bursts (FRBs). Using the MeerKAT radio telescope, we
conducted follow-up observations of the long-period radio transient GPM
J1839–10. Here we report the source exhibits a wide range of unusual
emission properties, including polarization characteristics indicative of
magnetospheric origin, linear-to-circular polarization conversion, and
drifting sub-structures closely resembling those observed in repeating
FRBs. These radio characteristics provide clear evidence in support of the
long-period magnetar model and establish the missing link between
long-period radio transients, magnetars, and FRBs.