Optical/UV Emission in the Tidal Disruption Event ASASSN-14li: Implications of Disc Modeling

We predict late-time optical/UV emission from tidal disruption events (TDEs) our slim accretion disc model \citep{Wen20} and explore the impact of black hole mass $M_\bullet$, spin $a_\bullet$, size. use these synthetic spectra to successfully fit multi-band \emph{Swift} observations ASASSN-14li at >350 days, setting only host galaxy extinction outer radius as free parameters employing inclination, rates derived fitting 10 epochs ASASSN-14li's X-ray with disc. To address nature \emph{early}-time emission, we consider two models: shock dissipation reprocessing. find that (1) predicted colour (e.g., $u-w2$) is insensitive unless spreads quickly; (2) a starburst required data, consistent post-starburst host; (3) surprisingly, $\approx$2$\times$ $\sim$constant late times, showing viscous spreading slow or non-existent; (4) can be self-consistent if $M_\bullet \lesssim 10^{6.75}$M$_\odot$, i.e., on low end $M_\bullet$ range ($10^{6.5-7.1}$M$_\odot$; 1$\sigma$ CL); larger masses require an unrealistically massive progenitor star; (5) gas needed for reprocessing, whether by quasi-static outflowing layer, $<0.5$M$_\odot$, (plausible) solar-mass star.