Circularization" vs. Accretion -- What Powers Tidal Disruption Events? (original) (raw)

A tidal disruption event (TDE) takes place when a star passes near enough to a massive black hole to be disrupted. About half the star's matter is given elliptical trajectories with large apocenter distances, the other half is unbound. To "circularize", i.e., to form an accretion flow, the bound matter must lose a significant amount of energy, with the actual amount depending on the characteristic scale of the flow measured in units of the black hole's gravitational radius (~ 10^{51} (R/1000R_g)^{-1} erg). Recent numerical simulations (Shiokawa et al., 2015) have revealed that the circularization scale is close to the scale of the most-bound initial orbits, ~ 10^3 M_{BH,6.5}^{-2/3} R_g ~ 10^{15} M_{BH,6.5}^{1/3} cm from the black hole, and the corresponding circularization energy dissipation rate is sim1044MBH,6.5−1/6\sim 10^{44} M_{BH,6.5}^{-1/6}sim1044MBH,6.5−1/6~erg/s. We suggest that the energy liberated during circularization, rather then energy liberated by accretion onto the black hole, powe...