Imprints of a galactic environment on TDEs: Suppressed peaks, shallower decays and late-time rebrightening episodes

Abstract

Classic models of tidal disruption events (TDEs), employing a purely Keplerian description of stellar debris dynamics, have proven remarkably successful in describing the observed early-time emission of these transients. By construction, however, this picture treats the disruption as an isolated star-black hole encounter, leaving the gravitational influence of the surrounding galaxy absent from the dynamics. We relax this assumption by embedding the debris within the gravitational field of a spherically symmetric mass distribution representing either the host galaxy or a dark matter halo, while deliberately retaining a minimal Newtonian framework so that the environmental contribution remains transparent and straightforward to interpret. Within this extended model, we find that the host potential can imprint clear signatures on the light curve that lie outside the predictive scope of traditional models, such as a suppressed initial accretion peak, phases of shallow decay and rebrightening episodes. For TDEs in ordinary galaxies, however, the latter signatures turns on far too late to be captured by current observations, explaining why simple Keplerian models have proven so effective despite neglecting the galactic environment. Only at much longer times does the broader galactic structure begin to reshape the fallback dynamics, gradually steering the system away from the canonical $t^{-5/3}$ decay. This provides an exciting opportunity for next-generation time-domain surveys to capture the long-term evolution of TDEs, enabling searches for delayed signals that encode information about the surrounding galactic mass.