Astrophysicists have found that a recently-discovered transient radio source, ILT J110160.52+552119.62, whose roughly minute-long pulses arrive with a periodicity of 125.5 min, is an red dwarf-white dwarf binary system with an orbital period that matches the period of the radio pulses, which are observed when the two stars are in conjunction.
Illustration of the radio waves emitted from the binary star systems: A white dwarf orbiting a red dwarf. Image credit: Danielle Futselaar / artsource.nl.
Astronomers detected in recent years radio pulses that lasted from seconds to minutes from sources within the Milky Way. The pulses produced by these sources are not what is expected of pulsars which emit pulses that last milliseconds. These so-called “long-period” transients are also periodic, but on timescales ranging from tens to hundreds of hours, not milliseconds as radio pulsars. The origins of the novel pulses have been hypothesized, but there is little evidence to support them. Charles Kilpatrick, an astrophysicist at Northwestern University, said that there are magnetars or highly magnetized neutron star sources which emit radio pulses every few seconds. Some astrophysicists have also argued sources may emit pulses regularly because they spin, and we can only detect the radio emission if we rotate source towards us.
Now, we know that at least some radio transients with long periods come from binaries.
We hope that this will motivate radio astronomers in their efforts to locate new sources, which might be derived from magnetar or neutron star binaries. They detected these pulses using a new imaging technique in data from the Low Frequency Array. The telescope, which acted as a radio camera of a larger size, was able to pinpoint the precise location of the source. The team estimates that the object lies 1,600 light years away, in Ursa Major. The Multiple Mirror Telescope of Arizona, with a 6.5-m-diameter mirror and the Hobby-Eberly Telescope located in Texas made follow-up observations that showed ILT J1101+5521 was not one star that flashed but rather two.
Two stars, one white dwarf orbiting a reddish dwarf, revolve around the same center of gravity once every 125.5 seconds. Researchers have suggested that there are at least two possible ways in which the stars could be generating the radio pulses. The radio pulses could either be caused by the powerful magnetic field of the star or the interaction between the two magnetic fields. Further observations will be needed to confirm this. This discovery has confirmed that compact objects, other than neutron star, can produce bright radio emissions, said Dr. Kaustubhrajwade. This discovery was reported today in Nature Astronomy (19459008).
_____
I. de Ruiter et al. Radio pulses from an orbiting white dwarf binary. Nat Astron, published online March 12, 2025; doi: 10.1038/s41550-025-02491-0
