Mystery of Long-Period Radio Signals from Dwarf Stars

For the very first time, we’ve captured visual proof of a white dwarf/red dwarf system as the source of strange periodic radio signals. 🔭

Astronomers have stumbled upon a red dwarf in a system that’s almost certainly the origin of a radio signal repeating every 125 minutes. Plus, there’s evidence suggesting a white dwarf companion. 💫 This finding adds weight to last year’s discoveries, confirming that such systems are behind these signals, though the exact mechanism still remains elusive. 🔍

Thanks to recent advancements in radio telescopes, astronomers have uncovered something resembling a “cosmic radio zoo” 🎇, sparking a race to trace the origin of these mysterious signals. One newly identified type is the “Long-Period Radio Transient” (LPRT), which can slow pulsars down by hundreds or even thousands of times. 🌌 At first, it was puzzling, but one LPRT—GLEAM-X J0704−37—was connected to a red dwarf that most likely orbits a white dwarf. 🧐

Artist’s depiction of red and white dwarfs orbiting, emitting a radio beam passing Earth.
Image credit: Daniëlle Futselaar/artsource.nl

📡 Now, there’s even stronger evidence pointing to the fact that many LPRTs might come from this process. However, Dr. Iris de Ruiter from the University of Sydney shared with IFLScience that this mission is far from complete. 🛸 “We can’t fully explain how this binary system produces signals, and I still question if all LPRTs can be explained this way,” she said. 🤔

Typically, pulsars, which are formed from neutron stars, emit radio signals so precise they can act as cosmic clocks. 🕰️ However, they gradually slow and weaken over time, which makes it impossible for them to generate long-period signals stronger than a few minutes. 📻

This makes the discovery of a pulsar-like object with an 18-minute period an intriguing mystery. 🤯 And the discovery of even longer-period signals only adds to the puzzle. 🎭 Initially, these discoveries were made near the galactic plane—the most studied area of the sky—but dense stars and dust clouds made pinpointing the source a challenge. 🌠

But while reanalyzing old data from the LOFAR telescope, Dr. de Ruiter found pulses from 2015 pointing toward Ursa Major. 🐻 This location, far from the galactic plane, was marked as ILTJ1101+5521. She managed to detect seven more pulses from ILTJ1101+5521, each lasting between 30 and 90 seconds, indicating it’s an LPRT with a 125-minute period. 📊

🔬 Follow-up observations didn’t pick up any radio signals but did spot a red dwarf right at that spot, 1,600 light-years away, with a 125-minute orbital period. The light from this system also revealed an unusually high amount of blue light for a red dwarf of its size. Researchers think this is due to a white dwarf being so close that it can’t be visually separated. 🔎

Dr. de Ruiter and her team concluded that the red and white dwarfs orbit each other with a 125-minute period, likely in a tidal interaction. 🌎✨ This means their rotation is synchronized with their orbit, with one side always facing the other. 🌀

💡 “It’s thrilling to add another piece to the puzzle,” Dr. de Ruiter said. “By collaborating with experts from various fields and using different observation methods, we’re inching closer to the answer, little by little.” 📚

Galactic plane showing LPRT (GLEAM-X) J162759.5-523504.3, illustrating signal tracing challenges.
Image credit: Dr Natasha Hurley-Walker (ICRAR/Curtin) and the GLEAM Team

🛸 One possible explanation is that a highly elliptical orbit generates signals when the stars are closest. But Dr. de Ruiter doubts this theory. 🤷‍♀️ While her team’s ability to measure orbital eccentricity is limited, she suspects the orbit is nearly circular, which is common for closely bound stars. 🌍

🌀 This points to the possibility that the signals could be continuously emitted, but like a lighthouse beam (or a typical pulsar), they sweep across space and are only detectable when directly pointing at us. 🏮

📄 The research paper was written before the findings on GLEAM-X J0704−37 were published. Dr. de Ruiter noted that the two systems are quite similar, except that GLEAM-X J0704−37 is farther away and hasn’t been observed showing the signature blue light of a white dwarf. 🧑‍🚀

🛠️ As to why the signal couldn’t be detected again, there could be several reasons. “It was only detected by LOFAR, so it’s possible the signal is brightest at very low radio frequencies,” Dr. de Ruiter explained. However, follow-up attempts with LOFAR didn’t detect anything. 📡

⚡ “Other LPRTs also show unpredictable behavior,” she observed. 🤨 To fully understand the cause, scientists need to figure out how red and white dwarfs interact to produce these rare but powerful radio emissions. 🔥

✍️ The researchers concluded, “We believe the radio signals come from the white dwarf or the interaction between the white and red dwarf.” They also suggested the magnetic field of the white dwarf might be synchronized with its orbit, although the exact process is still a mystery. ❓

📢 The team is eager to observe ILTJ1101+5521 in different wavelengths and find more examples. 🛸 “Some LPRTs have periods as short as 18 minutes, which might point to the existence of two different types,” Dr. de Ruiter added. 🤯

📜 This research was published in Nature Astronomy.

Ref : iflscience