THE SIMULATION OF NOVA EVOLUTION WITH OPTICALLY THICK WINDS

Thermonuclear runaways at the surface of a compact star, due to accret ion of nuclear fuel-rich matter, lead to expulsion of matter through o ptically thick winds. Simulations of such phenomena have relied either on stellar evolution codes, to which some ad hoc prescriptions for ma ss loss were added, or on integrations of the wind equations, with a s imilarly ad hoc prescription for the construction of a sequence of suc h solutions to represent an evolving explosion. A method is presented which combines the foregoing two extremes. The two-point boundary-valu e wind problem is solved by an efficient relaxation algorithm. And the wind solution is then used as an outer boundary condition in the stel lar code. The self-consistent combination of stellar evolution with an optically thick wind is sufficiently fast, and versatile, to handle t hermonuclear explosions near the surface of a compact star. An example is given of the simulation of a moderately fast (t(3) = 49 days) clas sical nova outburst. The entire wind phase can be followed in detail: the resulting visual light curve resembles those of actual moderately fast novae, and the expansion velocity is of the right magnitude.