VISTA variables in the Sagittarius dwarf spheroidal galaxy

I. McDonald (Univ. Manchester), A.A. Zijlstra (Univ. Manchester), G.C. Sloan (Cornell), E. Kerins (Univ. Manchester), E. Lagadec (Cornell), and D. Minniti (Pontifica Univ. Catolica de Chile)

2014, MNRAS, 439, 2618

Variability is examined in over 2.6 million objects covering 11 square degrees of the core of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) from VISTA Z-band observations. Pulsation amplitudes appear identical between red and asymptotic (RGB/AGB) giant stars, and between unreddened carbon and oxygen-rich stars. Generally, pulsation on the Sgr dSph giant branches follows the trends expected for the internal kappa mechanism. The dust-enshrouded carbon stars have the highest amplitudes of the stars we observe. Only in these stars does an external κ-mechanism-driven pulsation seem likely, caused by variations in their more-opaque carbon-rich dust. Variability is seen to increase roughly as a power law with increasing luminosity, as in other systems. In total, we identify 3,026 variable stars ( delta Z >~ 0.015 magnitudes, of which 176 are long-period variables associable with the upper giant branches of the Sgr dSph. We also identify 324 candidate RR Lyrae variables in the the Sgr dSph and 340 in the outer Galactic Bulge.

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Last modified 23 April, 2014. © Gregory C. Sloan and others.