New Binary Star System Discovered: A Key to Binary Evolution

Astronomers using the Tsinghua University-Ma Huateng Telescopes for Survey (TMTS) have unearthed a new binary star system, named TMTS J052610.43+593445.1. This intriguing system comprises an ultra-short-orbital-period binary with a subdwarf star and a white dwarf companion, located approximately 2,760 light years from Earth.

A Record-Breaking Discovery

The system's orbital period is about 20.5 minutes, positioning it as one of only five known binaries with such a short orbital period. The subdwarf star in the system is seven times larger than Earth and possesses a mass of 0.33 solar masses. This star is undergoing tidal deformation due to the gravitational pull of its companion, a carbon-oxygen white dwarf.

The White Dwarf Companion

The white dwarf, although ten times smaller than the sun, has a mass of 0.735 solar masses and an effective temperature of 25,400 K. This binary system presents astronomers with a unique opportunity to study the physics and evolution of stars under extreme conditions.

Decoding Binary Evolution

Current theories suggest that this binary is detached. However, in about 1.5 million years, the subdwarf will begin transferring mass to the white dwarf at an even shorter orbital period, leading to the formation of an AM CVn star through the helium-star channel. This process is pivotal for understanding binary evolution from the second common envelope ejection to the formation of AM CVn stars. The discovery of TMTS J052610.43+593445.1 could play a significant role in investigating these binary evolution paths.