A seven-Earth-radius helium-burning star inside a 20.5-min detached binary

Professor Xiaofeng Wang’s team at Tsinghua University and their collaborators (including Péter Németh from the Stellar Department of the Astronomical Institute in Ondřejov) have made a ground-breaking discovery using the Tsinghua University-Ma Huateng Telescope for Survey (TMTS) — a compact binary star system with the ultra-short orbital period of only 20.5 minutes (known as TMTS J0526), located about 2760 light-years from Earth, and they uncovered its physical origin. This system comprises a carbon-oxygen white dwarf star, with a mass of about 0.74 solar mass, coupled with a hot subdwarf star with a mass of about 0.33 solar mass. This remarkable binary is poised to become an important source of milli-Hertz gravitational waves, detectable by upcoming space observatories, such as LISA, TianQin, and Taiji. The finding also validates the low-mass hot subdwarf star formed from the second common-envelope ejection channel (initially proposed by Prof. Zhanwen Han and his collaborators from the Yunnan Observatories, Chinese Academy of Sciences).

More details of this work can be found at astroserver.org.

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