It grows larger, it grows hotter, channeling mass in a never-ending spiral.
Mass accretion occurs when two stars are so close that one of them absorbs mass from the outer layers of the other. The stolen matter swirls around the strongest star, in a brightly shining whirlpool of molecules and cosmic dust. A small but dense neutron star can easily devour a red giant. This fatal dance intertwines their destiny and may result in a supernova, a tremendous explosion that destroys them both.
How do binary stars interact?
Look at this simulation from NASA!