We argue that both the extreme soft X-ray excess and the large-amplitude variability of narrow-line Seyfert 1 galaxies ( NLS1s ) can be explained in the framework of the slim disk model .
When the disk luminosity approaches the Eddington luminosity , the disk becomes a slim disk , exhibiting a multi-color blackbody spectrum with a maximum temperature , T _ { bb } , of \sim 0.2 ( M / 10 ^ { 5 } M _ { \odot } ) ^ { -1 / 4 } keV , and size of the X-ray emitting region , r _ { bb } , of \sim r _ { S } ( the Schwarzschild radius ) .
Furthermore , magnetic energy can be amplified up to a level exceeding radiation energy emitted from the disk , causing substantial variability in X-rays by consecutive magnetic flares .