Red Dwarf Caught Slowly Consuming a Brown Dwarf Companion

• Astronomers have observed a binary star system, ZTF J0440+2325, where a red dwarf is slowly accreting material from its brown dwarf companion.
• Unlike typical stellar interactions where a star quickly destroys and engulfs its smaller companion, this system features a long-lived, stable transfer of mass.

System Characteristics

• Located 300 light-years away, the system was identified using archival data from the Zwicky Transient Facility (ZTF).
• The brown dwarf orbits the red dwarf every 87 minutes, with an orbital path smaller than the diameter of the Sun.
• The system exhibits a unique triangular light curve, which researchers initially struggled to explain as it did not match known patterns for Black Widow Binaries.

Mechanism of Mass Transfer

• Instead of forming an accretion disk, material from the brown dwarf slams directly onto the red dwarf's surface at high speed, creating a perpetual hotspot.
• The triangular signal is caused by this hotspot appearing and disappearing from view as the brown dwarf orbits the red dwarf.
• The M dwarf has a mass of approximately 85 Jupiters, while the brown dwarf has roughly 25 Jupiters.
• Mass is transferred at a rate of about 1/100,000 of an Earth mass per year, a process that is expected to continue for billions of years.

Implications and Future Research

• This marks the first confirmed observational evidence of a low-mass star actively and steadily accreting mass from another low-mass object.
• Researchers plan to use the upcoming Vera Rubin Observatory’s Legacy Survey of Space and Time to find more systems with similar light signatures, helping to better understand how planets and brown dwarfs interact with their host stars.