The high-energy probability distribution of accretion disc luminosity fluctuations

The probability density function of accretion disc luminosity fluctuations at high observed energies (i.e., larger than the peak temperature scale disc) is derived, under assumption that are log-normally distributed. Thin theory used throughout. While log-normal would imply disc's bolometric also log-normal, Wien-like behaves very differently. For example, in contrast to a distribution, standard deviation derived distribution not linearly proportional its mean. This means these systems do follow linear rms-flux relationship. Instead they exhibit intrinsic variance, and undergo what amounts phase transition, which mode (in statistical sense) ceases exist, even for physically reasonable values underlying variance. moments this using asymptotic expansion techniques. A result important interpreting observations predicts fractional variability should increase as frequency increased. will be practical utility quantitatively understanding above their scale, including X-ray tidal disruption events.