Localized thermonuclear runaways and volcanoes on degenerate dwarf stars

A unified thermonuclear-runaway mechanism for dwarf and classical novae is considered that involves thermonuclear-powered 'volcanic' (or localized) eruptions accompanied by hot bright 'lava' flows on the surfaces of white dwarfs in some binary systems. Energy-transport and thermonuclear-runaway time scales in degenerate dwarf envelopes are compared, and it is shown that localized, rather than global, eruptions often occur. The envelope and white dwarf masses that lead to localized thermonuclear runaways (LTNR's) are estimated. LTNR's on neutron stars are briefly considered. Order-of-magnitude estimates are given for the eruption, flow, and shutdown characteristics of a white dwarf LTNR. It is suggested that LTNR's are likely to recur with time scales of weeks or months and that the end product of such evolution might be a Type I supernova.