Extremely Relativistic Tidal Disruption Events

Taeho Ryu, Julian Krolik, Tsvi Piran

Submitted on 31 October 2022


Extreme tidal disruption events (eTDEs), which occur when a star passes very close to a supermassive black hole, may provide a way to observe a long-sought general relativistic effect: orbits that wind several times around a black hole and then leave. Through general relativistic hydrodynamics simulations, we show that such eTDEs are easily distinguished from most tidal disruptions, in which stars come close, but not so close, to the black hole. Following the stellar orbit, the debris in eTDEs is initially distributed in a crescent that quickly turns into tight spirals, from which some mass later falls back toward the black hole, while the remainder is ejected. Internal shocks within the infalling debris power the observed emission. The resulting light-curve rises rapidly to roughly the Eddington luminosity, maintains this level for between a few weeks and a year (depending on both the stellar mass and the black hole mass), and then drops. Most of its power is in thermal X-rays at a temperature 106 K (100 eV). The debris evolution and observational features of eTDEs are qualitatively different from ordinary TDEs, making eTDEs a new type of TDE. Although eTDEs are relatively rare for lower-mass black holes, most tidal disruptions around higher-mass black holes are extreme. Their detection offers a view of an exotic relativistic phenomenon previously inaccessible.


Comment: 10 pages, 3 figures, submitted to ApJL, comments welcome

Subject: Astrophysics - High Energy Astrophysical Phenomena


The solid white curve depicts the geodesic of an orbit with $r_{\rm p} \simeq 4.03 r_{\rm g}$ around a black hole (red disk at the center); the arrow indicates the direction of the orbit. Colorscale shows the density distribution of stellar debris 241~s before a star whose center of mass follows this geodesic passes through pericenter.