  Large amplitude, high luminosity soft X-ray flares were detected by the ROSAT
All-Sky Survey in several galaxies with no evidence for Seyfert activity in
their ground-based optical spectra. These flares had the properties predicted
for a tidal disruption event by a central supermassive black hole: soft X-ray
spectrum, time-scale of months, and large X-ray luminosity (10^42 - 10^44 ergs
s^-1). In order to evaluate the alternative hypothesis that these flares could
have been some form of extreme AGN variability, we obtained follow-up optical
spectroscopy of three of the flaring galaxies a decade later with the Space
Telescope Imaging Spectrograph (STIS) and a narrow slit to search for or place
stringent limits on the presence of any persistent Seyfert-like emission in
their nuclei. Two of the galaxies, RX J1624.9+7554 and RX J1242.6-1119, show no
evidence for emission lines or a non-stellar continuum in their Hubble Space
Telescope (HST) nuclear spectra, consistent with their ground-based
classification as inactive galaxies. They remain the most convincing as hosts
of tidal disruption events. NGC 5905, previously known as a starburst H II
galaxy due to its strong emission lines, has in its inner 0."1 a nucleus with
narrow emission-line ratios requiring a Seyfert 2 classification. This weak
Seyfert 2 nucleus in NGC 5905, which was masked by the many surrounding H II
regions in ground-based spectra, requires a low level of prior non-stellar
photoionization, thus raising some uncertainty about the nature of its X-ray
flare, which may or may not have been a tidal disruption event. The absence of
both broad emission lines and nuclear X-ray absorption in NGC 5905 also
characterizes it as a ``true'' Seyfert 2 galaxy, yet one that has varied by
more than a factor of 100 in X-rays.
