2024ApJ...974..165H

The rising part of a tidal disruption event light curve provides unique insight into early emission and the onset of accretion. Various mechanisms are proposed to explain the pre-peak emission, including shocks from debris interaction and reprocessing of disk emission. We study the pre-peak emission and its influence on the gas circularization by a series of gray radiation hydrodynamic simulations with varying black hole mass. We find that, given a super-Eddington fallback rate of $10{\dot{M}}_{\mathrm{Edd}}$, the stream-stream collision can occur multiple times and drive strong outflows of up to $9{\dot{M}}_{\mathrm{Edd}}$. By dispersing gas to ≳100r_s, the outflow can delay gas circularization and leads to sub-Eddington accretion rates during the first few stream-stream collisions. The stream-stream collision shock and circularization shock can sustain a luminosity of ∼10⁴⁴ erg s^–1 for days. The luminosity is generally sub-Eddington and shows a weak correlation with accretion rate at early times. The outflow is optically thick, yielding a reprocessing layer with a size of ∼10¹⁴ cm and photospheric temperature of ∼4 × 10⁴ K.