An international team of astronomers has traced a series of mysterious radio pulses to a binary system consisting of a white dwarf and a red dwarf. The discovery marks the first time that radio pulses have been traced to such a binary source. The study, which will be published in Nature Astronomy, involved researchers from Northwestern University and the University of Sydney.
The astronomers detected a constant stream of radio pulses every two hours coming from the direction of the Big Dipper. After analyzing data from multiple telescopes, they identified the source as a tightly orbiting pair of stars whose magnetic fields interact, emitting long radio blasts.
Northwestern astrophysicist Charles Kilpatrick explained, “There are several highly magnetized neutron stars, or magnetars, that are known to exhibit radio pulses with a period of a few seconds.” He added that this new discovery shows that stars within binary systems can also emit long-period radio bursts.
Iris de Ruiter, who led the study while at the University of Amsterdam and is now at the University of Sydney, first discovered these pulses in archives from the Low Frequency Array (LOFAR). She found seven distinct pulses dating back to 2015. These radio signals repeat like clockwork every two hours.
Kilpatrick noted, “The radio pulses are very similar to FRBs, but they each have different lengths.” He pointed out that these pulses have lower energies than fast radio bursts (FRBs) and last for several seconds instead of milliseconds.
Further observations from Arizona's MMT Observatory and Texas's McDonald Observatory confirmed that two stars were responsible for these signals. Located 1,600 light-years away, they orbit each other every 125.5 minutes. Kilpatrick used remote access to observe their full cycle and confirmed that the red dwarf's movement matched the pulse period.
By measuring variations in motion, Kilpatrick calculated the mass of the fainter companion star, identifying it as a white dwarf. This supports hypotheses about long-period radio transients originating from such binaries.
Future studies will focus on ultraviolet emissions from this binary system named ILTJ1101 to learn more about its characteristics. De Ruiter expressed satisfaction with piecing together this puzzle with experts across various astronomical disciplines.
The research was based partly on data from the International LOFAR Telescope (ILT), constructed by ASTRON.