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Variability is examined in over 2.6 million stars covering 11 square degreesof the core of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) from VISTAZ-band observations. Generally, pulsation on the Sgr dSph giant branchesappears to be excited by the internal kappa mechanism. Pulsation amplitudesappear identical between red and asymptotic (RGB/AGB) giant stars, and betweenunreddened carbon and oxygen-rich stars at the same luminosity. The lack ofcorrelation between infrared excess and variability among oxygen-rich starsindicates pulsations do not contribute significantly to wind driving inoxygen-rich stars in the Sgr dSph, though the low amplitudes of these starsmean this may not apply elsewhere. The dust-enshrouded carbon stars have thehighest amplitudes of the stars we observe. Only in these stars does anexternal kappa-mechanism-driven pulsation seem likely, caused by variations intheir more-opaque carbon-rich molecules or dust. This may allow pulsationdriving of winds to be effective in carbon stars. Variability can be simplifiedto a power law (amplitude proportional to L/T^2), as in other systems. Intotal, we identify 3026 variable stars (with r.m.s. variability of delta Z >~0.015 magnitudes), of which 176 are long-period variables associable with theupper giant branches of the Sgr dSph. We also identify 324 candidate RR Lyraevariables in the the Sgr dSph and 340 in the outer Galactic Bulge.

VISTA variables in the Sagittarius dwarf spheroidal galaxy: pulsation- vs. dust-driven winds on the giant branches