Team led by China uncovers unique binary gravitational wave source

A recent discovery of a binary star system, comprised of a white dwarf and a hot subdwarf, has excited the scientific community. Record-breaking orbital speed was observed between the two celestial bodies.

These stars are expected to emit strong gravitational wave radiation in the milli-Hertz frequency range, a phenomenon anticipated to be picked up by future space-based gravitational wave observatories.

The team of Professor Wang Xiaofeng at Tsinghua University, along with his collaborators, made this discovery utilizing the Tsinghua University-Ma Huateng Telescope for Survey (TMTS). The TMTS is stationed at the Xinglong Observatory of the National Astronomical Observatories in Hebei Province, north China. The findings were made public online in Nature Astronomy on Friday.

The researchers uncovered an extraordinarily distinct 20.5-minute orbital-period binary system approximately 2,760 light years from Earth, termed TMTS J0526. This system comprises of a carbon-oxygen white dwarf star and a low-mass subdwarf B star with a celestial mass of just 0.33 solar mass.

The hot subdwarf component of the TMTS J0526 system has a radius merely seven times that of our planet, making it the star with the smallest known volume, states Lin Jie, a principal member of the research group.

"This discovery has unearthed a significant source for upcoming space-based gravitational wave detection, affirming theoretical predictions about the formation of such an exceptional binary system. These predictions were proposed by Han Zhanwen's team from the Yunnan Observatory back in 2003," said Wang Xiaofeng.

He further added, "This discovery paves the way for refining our knowledge and theories on stellar evolution, an important linchpin in our comprehension of the universe's evolution."

The TMTS, a uniquely designed multi-telescope optical survey instrument, was established by Professor Wang's team, with considerable support from the Ma Huateng Foundation and Tsinghua University.

Since its commissioning in 2020, the TMTS has been actively scanning the northern celestial hemisphere at a cadence of roughly a minute.

By the close of 2023, the TMTS had collected photometric data for well over 27 million stars, encapsulating dozens of valuable short-period variable sources. Out of the amassed data, TMTS J0526 emerges as one of the sources with the most compressed period.