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The Nature of the Supersoft X-ray Sources: 

The Nature of the Supersoft X-ray Sources Katherine McGowan (MSSL) Phil Charles (SAAO), Alex Blustin (MSSL), Mario Livio (STScI), Darragh O’Donoghue (SAAO), Bernard Heathcote (Barfold Observatory)

Supersoft Source Characteristics: 

Supersoft Source Characteristics Luminous emission at very soft energies LX ~ 1037 - 1038 erg s-1 < 0.5 keV Greiner et al. 1991

White Dwarf Model: 

White Dwarf Model Binary system white dwarf compact object sub-giant companion High accretion rate ~ 100 - 1000 higher than in CVs > 10-7 Msun yr-1 Near-Eddington luminosities achieved as white dwarf burns hydrogen steadily at its surface van den Heuvel et al. 1992

RX J0513.9-6951: 

RX J0513.9-6951 X-rays detected only during optical low states

Model for X-ray Outbursts: 

Model for X-ray Outbursts Regular thermonuclear flash model radius expansion increase in optical luminosity Contraction model accretion rate drops decrease in optical luminosity rise in effective temperature increase in X-ray luminosity Southwell et al. 1996

Optical Monitoring: 

Optical Monitoring

Multi-wavelength Data: 

Multi-wavelength Data UV Optical X-ray Hardness ratio (0.5-0.8 keV) (0.3-0.5 keV)

Low-resolution X-ray Spectra: 

Low-resolution X-ray Spectra Absorption

Spectral Evolution: 

Spectral Evolution kT LBB RBB LX

High-resolution X-ray Spectra: 

High-resolution X-ray Spectra

Summary 1: 

Summary 1 Contraction model based on prediction that rise in X-rays occurs after drop in optical Detect X-rays in optical low state X-ray flux and temperature decrease as optical low state progresses As X-ray outburst evolves peak of emission moves into UV Radius decreases at start of observations As optical/UV intensity recover radius increases

Summary 2: 

Summary 2 Highly ionized gas outflowing at <3000 km/s Optical depth of ionized absorption increases Viewing system close to pole-on through bipolar outflow, intrinsic covering factor of outflow changes? Seeing process of expansion, highly ionized nova by-products stream out from surface and build into optically-thick inflated surface? increase in optical/UV flux occurs as X-rays are down-scattered in inflated layer?

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