We investigated, through numerical models, the flaring variability that may
arise from the rotation of maser clouds of approximately spheroidal geometry,
ranging from strongly oblate to strongly prolate examples. Inversion solutions
were obtained for each of these examples over a range of saturation levels from
unsaturated to highly saturated. Formal solutions were computed for rotating
clouds with many randomly chosen rotation axes, and corresponding averaged
maser light curves plotted with statistical information. The dependence of
results on the level of saturation and on the degree of deformation from the
spherical case were investigated in terms of a variability index and duty
cycle. It may be possible to distinguish observationally between flares from
oblate and prolate objects. Maser flares from rotation are limited to long
timescales (at least a few years) and modest values of the variability index
(≲100), and can be aperiodic or quasi-periodic. Rotation is therefore
not a good model for H2O variability on timescales of weeks to months, or of
truly periodic flares.Comment: 11 pages, 12 figures, accepted for publication in MNRA
