  Liu and collaborators recently proposed an elliptical accretion disk model
for tidal disruption events (TDEs). They showed that the accretion disks of
optical/UV TDEs are large and highly eccentric and suggested that the broad
optical emission lines with complex and diverse profiles originate in the cool
eccentric accretion disk of random inclination and orientation. In this paper,
we calculate the radiation efficiency of the elliptical accretion disk and
investigate the implications for the observations of TDEs. We compile
observational data for the peak bolometric luminosity and total radiation
energy after peak brightness of 18 TDE sources and compare these data to the
predictions from the elliptical accretion disk model. Our results show that the
observations are consistent with the theoretical predictions and that the
majority of the orbital energy of the stellar debris is advected into the black
hole (BH) without being converted into radiation. Furthermore, we derive the
masses of the disrupted stars and the masses of the BHs of the TDEs. The BH
masses obtained in this paper are also consistent with those calculated with
the $M_{\rm BH} - \sigma_*$ relation. Our results provide an effective method
for measuring the masses of BHs in large numbers of TDEs to be discovered in
ongoing and next-generation sky surveys, regardless of whether the BHs are
located at the centers of galactic nuclei or wander in disks and halos.
