The Delay Time Distribution of Tidal Disruption Flares
  Recent observations suggest that stellar tidal disruption events (TDE) are
strongly overrepresented in rare, post-starburst galaxies. Several dynamical
mechanisms have been proposed to elevate their TDE rates, ranging from central
stellar overdensities to the presence of supermassive black hole (SMBH)
binaries. Another such mechanism, introduced here, is a radial velocity
anisotropy in the nuclear star cluster produced during the starburst. These,
and other, dynamical hypotheses can be disentangled by comparing observations
to theoretical predictions for the TDE delay time distribution (DTD). We show
that SMBH binaries are a less plausible solution for the post-starburst
preference, as they can only reproduce the observed DTD with extensive
fine-tuning. The overdensity hypothesis produces a reasonable match to the
observed DTD (based on the limited data currently available), provided that the
initial stellar density profile created during the starburst, $\rho(r)$, is
exceptional in both steepness and normalization. In particular, explaining the
post-starburst preference requires $\rho \propto r^{-\gamma}$ with $\gamma
\gtrsim 2.5$, i.e. much steeper than the classic Bahcall-Wolf equilibrium
profile of $\gamma = 7/4$. For "ultrasteep" density cusps ($\gamma \ge 9/4$),
we show that the TDE rate decays with time measured since the starburst as
$\dot{N} \propto t^{-(4\gamma-9)/(2\gamma-3)} / \ln t$. Radial anisotropies
also represent a promising explanation, provided that initial anisotropy
parameters of $\beta_0 \approx 0.5$ are sustainable against the radial orbit
instability. TDE rates in initially anisotropic cusps will decay roughly as
$\dot{N} \propto t^{-\beta_0}$. As the sample of TDEs with well-studied host
galaxies grows, the DTD will become a powerful tool for constraining the
exceptional dynamical properties of post-starburst galactic nuclei.
