The emission of interpulses by a 6.45-h-period coherent radio transient

Long-period radio transients are a new class of astronomical objects characterized by prolonged periods ranging from 18 min to 54 min. They exhibit highly polarized, coherent, beamed radio emission lasting only 10–100 s. The intrinsic nature of these objects is subject to speculation, with highly magnetized white dwarfs and neutron stars being the prevailing candidates. Here we present ASKAP J183950.5−075635.0, boasting the longest known period of this class at 6.45 h. It exhibits emission characteristics of an ordered dipolar magnetic field, with pulsar-like bright main pulses and weaker interpulses offset by about half a period that are indicative of an oblique or orthogonal rotator. This phenomenon, observed in a long-period radio transient, confirms that the radio emission originates from both magnetic poles and that the observed period corresponds to the rotation period. The spectroscopic and polarimetric properties of ASKAP J183950.5−075635.0 are consistent with a neutron star origin, and this object is a crucial piece of evidence in our understanding of long-period radio sources and their links to neutron stars. Coherent radio emission with a long (nearly 6.5 h) period has been detected from both magnetic poles of a rotating compact object, offering insights into the evolution and emission mechanism of compact radio transients.