Binary Stars Identified as the Engine Behind Interacting Supernovae

• Interacting supernovae are notable for their extended luminosity, lasting years rather than months, due to high-energy debris colliding with dense circumstellar material (CSM).
• A new study published in The Astrophysical Journal Letters, led by Sung-Han Tsai of Academia Sinica, identifies binary star interactions as the origin of this surrounding gas.

Research Findings

• Researchers modeled binary stellar evolution and discovered that "Case C mass transfer" is the mechanism behind CSM formation.
• As a massive star nears the end of its life, it expands and overflows its Roche lobe, transferring outer-layer material onto a binary companion.
• Some of this material escapes to form a dense cocoon of CSM, which later acts as fuel for the supernova explosion's shockwave, converting kinetic energy into prolonged, intense light.

Implications and Significance

• The study suggests that donors with 10–20 M⊙ in binaries with specific separations undergo this transfer within roughly 1,000 years of core collapse.
• This mechanism is estimated to account for approximately 13% of all core-collapse supernovae (CCSNe).
• This model provides a consistent explanation for observed events like SN 2014C, resolving previous difficulties in accounting for extended luminosity without needing to assume unrealistic quantities of radioactive 56Ni.
• Future refinements will focus on the geometry and dynamics of Roche lobe overflow and how radiative cooling influences the spatial distribution and density of the CSM.