Rapid Dust Formation in Binary Star Interactions

Recent simulations have provided insights into the formation of dust during common envelope interactions between binary stars. The research, titled "Dust formation in common envelope binary interactions -- II: 3D simulations with self-consistent dust formation," was conducted by Luis C. Bermúdez-Bustamante and colleagues. The study focuses on the interactions between thermally-pulsing asymptotic giant branch (AGB) stars and a compact companion star, revealing that dust formation occurs rapidly within a few years after the onset of the common envelope phase.

Key findings include:

• Dust grains begin to form approximately 1 to 3 years after the interaction starts, creating an optically thick shell at distances of about 10 to 20 astronomical units (au) from the stars.
• Over a span of around 40 years, this shell expands significantly, reaching thicknesses and radii of approximately 400 to 500 au, with temperatures around 400 K.
• The total dust yield from the interactions is estimated at about 0.0084 solar masses for a 1.7 solar mass AGB star and 0.022 solar masses for a 3.7 solar mass AGB star, indicating a nucleation efficiency close to 100% if no dust destruction mechanisms are considered.
• Notably, the dust forms a thousand times faster in these common envelope interactions compared to single AGB stars, which typically take tens of thousands of years for similar dust formation.

These rapid dust formation processes may influence the infrared spectral energy distribution observed in certain optical transients, such as luminous red novae. The findings support the hypothesis that extreme carbon stars and "water fountains" could be observed following common envelope events. The full paper can be accessed through arXiv with the identifier arXiv:2401.03644.