Program: GS-2025A-Q-311

Post-asymptotic giant branch (post-AGB) stars occur in a fast evolutionary stage in evolved low-mass stars, and are thus rare objects. This notwithstanding, a handful of them have been detected in Galactic globular clusters (GCs). Recently, Kumar et al. (2024) proposed the existence of a binary post-AGB star in the low-mass GC E3. If confirmed, this would be the first of its kind in a GC, thus helping shed light on their (still uncertain) formation scenarios. We propose a GMOS radial velocity campaign to either firmly establish its orbit, reject its binary nature, or (at a minimum) place strong constraints on the star's binary parameters.