  Observations of heavy metal pollution in white dwarf stars indicate that
metal-rich planetesimals are frequently scattered into star-grazing orbits,
tidally disrupted, and accreted onto the white dwarf surface, offering direct
insight into the dynamical evolution of post-main-sequence exoplanetary
systems. Emission lines from the gaseous debris in the accretion disks of some
of these systems show variations on timescales of decades, and have been
interpreted as the general relativistic precession of recently formed,
elliptical disk. Here we present a comprehensive spectroscopic monitoring
campaign of the calcium infrared triplet emission in one system, HE 1349--2305,
which shows morphological emission profile variations suggestive of a
precessing, asymmetric intensity pattern. The emission profiles are shown to
vary on a timescale of one to two years, which is an order of magnitude shorter
than what has been observed in other similar systems. We demonstrate that this
timescale is likely incompatible with general relativistic precession, and
consider alternative explanations for the rapid evolution including the
propagation of density waves within the gaseous debris. We conclude with
recommendations for follow-up observations, and discuss how the rapid evolution
of the gaseous debris in HE 1349--2305 could be leveraged to test theories of
exoplanetary debris disk evolution around white dwarf stars.
