  We have analyzed archival spectra of the hot UV-bright star ZNG 1 in the
globular cluster M5 (NGC 5904) obtained with the Far Ultraviolet Spectroscopic
Explorer (FUSE) and the Space Telescope Imaging Spectrograph (STIS). From these
data, we derive an effective temperature $T_{\rm eff} = 43{,}000 \pm 1400$ K, a
surface gravity $\log g = 4.47 \pm 0.08$, a rotational velocity $v \sin i = 157
\pm 12$ km s$^{-1}$, and a mass $M = 0.92 \pm 0.17 \, M_{\odot}$. The
atmosphere is helium-rich ($Y = 0.99$) and enhanced in CNO (relative to the
cluster). The spectrum exhibits wind features with a terminal velocity near
1500 km s$^{-1}$ and strong discrete absorption components (DACs). The high
helium abundance, stellar mass, and rotational velocity suggest that the star
is a merger remnant, and its parameters are consistent with models of a pair of
merging He-core white dwarfs.
