A model of the symbiotic star RX Puppis.

RX Puppis is a key object in unravelling the nature of the dust-shrouded mira symbiotic stars because of its gross spectral variability. A summary catalog of the major observed features of RX Pup is provided, and then, a model which accounts for all of them is presented. In the present model, a white dwarf has been accreting slowly from the mass-loss wind of a distant mira companion. The accreted material has ignited in a shell flash of many decades duration, and now has a luminosity close to the Eddington value. Mass loss is radiatively driven from the white dwarf and is highly variable. When most extreme, the photosphere expands, the effective temperature falls to 20,000 K, and the star enters a low-excitation phase. The radio emission fades gradually due to recombination. Mass loss from the white dwarf began to fall almost a decade ago; the system is still adjusting to the increased ultraviolet flux and to the changing position of the standing shock where the pressures in the winds from the two stars balance.