X-ray Evolution of Classical Novae: Timescales for the SSS Phase

The outbursts of novae are driven by a thermonuclear runaway at the base of anaccreted shell. Soft Xray emission resulting from high surface temperatures onthe WD after outburst are expected, but seldom observed (SSS phase). Some novaeenter the SSS phase within the first year after outburst, and quickly turn offthereafter (the very fast ONeMg novae). Others (e.g., slow novae) are delayedyears after outburst before entering the SSS stage, which then lasts many years.ROSAT detected only 3 novae in their SSS state; XMM has observed 5, 3 which haveSSS spectrums. Insight into the diversity and evolution of novae can be gainedby determining when (or if) the SSS stage begins, when turnoff occurs, and howthis relates to composition and the mass of the WD. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]