Characterization and Evolution of the Supersoft X-ray Phase of Classical Novae

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 a year after outburst, and quickly turn offthereafter (very fast ONeMg novae). Slow novae are delayed years after outburstbefore entering the SSS stage, which then last many years. ROSAT detected only 3novae in their SSS state; XMM has now observed virgul5. Insight into diversity andevolution of novae can be gained by determining when (or if) the SSS stagebegins, when turnoff occurs, and how this relates to composition and the mass ofthe WD. We propose to observe a dozen novae to charaterize their xray emission and SSS timescales. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]