  As a step towards clarifying the ionization mechanism of LINERs, we have used
the Hubble Space Telescope Faint Object Spectrograph to obtain an ultraviolet
spectrum of the nucleus of NGC 6500. Compared with more luminous Seyfert
nuclei, the emission-line spectrum of NGC 6500 is remarkable for its
low-excitation character: C III], C II], and Mg II are the strongest
collisionally excited lines in the UV, and C IV is not detected. The fast shock
models of Dopita & Sutherland (1995, 1996) are a poor match to the observed
spectrum, as they predict much stronger emission than is observed for
high-excitation lines such as C IV. Photoionization by an obscured nonstellar
continuum source, or possibly ionization by slower (100 km/s) shocks, are more
likely explanations for the emission-line ratios. The origin of the UV
continuum is unclear; its overall spectral shape is reasonably well matched by
spectral evolution models for single-burst populations with ages in the range
70-100 Myr, but no definite absorption features from young stars are present.
Alternately, the UV continuum (or some fraction of it) may be scattered
radiation from a hidden active nucleus. We tentatively detect a broad He II
4686 emission feature, which may be due to Wolf-Rayet stars, although the UV
spectrum does not show any clear Wolf-Rayet signatures. We also find that NGC
6500 is weakly detected in an archival ROSAT HRI image with a luminosity of 5 x
10^40 erg/s in the 0.1-2.4 keV band, within the normal range for LINERs.
