The Turbulent Architecture and Convective Drivers of Mass Transfer in a Red Supergiant Binary

Abstract: Mass transfer from evolved stars like red supergiants (RSGs) is a crucial process governing massive binary evolution, yet the physical mechanisms shaping the outflow at the convective stellar surface remain poorly understood. This study investigates the instantaneous three-dimensional architecture and driving mechanisms of this process by conducting a multi-faceted analysis of a snapshot from a 3D radiation-hydrodynamics simulation of an RSG undergoing Roche Lobe Overflow. Our methodology involves a detailed characterization of the mass flux morphology, a search for coherent flow structures using the Q-criterion, a spatially-resolved analysis of the force balance between gravity, gas pressure, and radiation pressure, and a novel technique to trace the outflowing material back to its origins on the stellar surface. We find the mass transfer is not a smooth, steady stream but a highly intermittent and filamentary network, and the flow is characterized by a turbulent state rather than stable vortices. Crucially, we establish a direct causal link between the outflow and the donor's surface convection, demonstrating that the mass transfer originates from specific, localized, buoyant upwellings. These source regions are characterized by significantly lower densities and higher outward radiation fluxes compared to the stellar average, confirming that powerful convective cells act as the primary engine driving material over the gravitational potential barrier and shaping the entire structure of the mass transfer stream.

Subjects:	astro-ph.CO; cs.LG
Cite as:	PX:2508.00016