Systematic light curve modelling of TDEs: statistical differences
  between the spectroscopic classes
  With the sample of observed tidal disruption events (TDEs) now reaching
several tens, distinct spectroscopic classes have emerged: TDEs with only
hydrogen lines (TDE-H), only helium lines (TDE-He), or hydrogen in combination
with He II and often N III/O III (TDE-H+He). Here we model the light curves of
32 optically-bright TDEs using the Modular Open Source Fitter for Transients
(MOSFiT) to estimate physical and orbital properties, and look for statistical
differences between the spectroscopic classes. For all types, we find a shallow
distribution of star masses, compared to a typical initial mass function,
between $\sim 0.1-1$ M$_\odot$, and no TDEs with very deep ($\beta \gg 1$)
encounters. Our main result is that TDE-H events appear to come from less
complete disruptions (and possibly lower SMBH masses) than TDE-H+He, with
TDE-He events fully disrupted. We also find that TDE-H events have more
extended photospheres, in agreement with recent literature, and argue that this
could be a consequence of differences in the self-intersection radii of the
debris streams. Finally, we identify an approximately linear correlation
between black hole mass and radiative efficiency. We suggest that TDE-H may be
powered by collision-induced outflows at relatively large radii, while TDE-H+He
could result from prompt accretion disks, formed more efficiently in closer
encounters around more massive SMBHs.
