  The subject of micro-variability among Mira stars has received increased
attention since DeLaverny et al. (1998) reported short-term brightness
variations in 15 percent of the 250 Mira or Long Period Variable stars surveyed
using the broadband 340 to 890 nm Hp filter on the HIPPARCOS satellite. The
abrupt variations reported ranged 0.2 to 1.1 magnitudes, on time-scales between
2 to 100 hours, with a preponderance found nearer Mira minimum light phases.
However, the HIPPARCOS sampling frequency was extremely sparse and required
confirmation because of potentially important atmospheric dynamics and
dust-formation physics that could be revealed. We report on Mira light curve
sub-structure based on new CCD V and R band data, augmenting the known light
curves of Hipparcos-selected long period variables [LPVs], and interpret same
in terms of [1] interior structure, [2] atmospheric structure change, and/or
[3] formation of circumstellar [CS] structure. We propose that the alleged
micro-variability among Miras is largely undersampled, transient overtone
pulsation structure in the light curves.
