A full relativistic thin disc – the physics of the plunging region and the value of the stress at the ISCO

The widely used Novikov-Thorne relativistic thin disc equations are only valid down to the radius of innermost stable circular orbit (ISCO). This leads an undetermined boundary condition at ISCO, known as inner stress disc, which sets luminosity ISCO and introduces considerable ambiguity in accurately determining mass, spin accretion rate black holes from observed spectra. We resolve this by self-consistently extending solution through hole horizon calculating inspiral average particle subject turbulent forces, using a new particle-in-disc technique. Traditionally it has been assumed that is zero, with material plunging approximately radially into close speed light. demonstrate fact less severe, several (~4-17) orbits completed before horizon. small non-zero inside local surface temperature between ~0.15 0.3 times maximum case where no dynamically important net magnetic field present. For range parameters we calculate value stress/surface temperature, required when fitting models observations. problem slim heating becomes inaccurate falls zero region.