Precision Holography for $\mathcal{N}=2^{\ast }$ on $S^4$ from type IIB Supergravity

We find a new supersymmetric solution of type IIB supergravity which is holographically dual to the planar limit of the four-dimensional $\mathcal{N}=2^{\ast }$ supersymmetric Yang-Mills theory on $S^4$. We study a probe fundamental string in this background which is dual to a supersymmetric Wilson loop in the $\mathcal{N}=2^{\ast }$ theory. Using holography we calculate the expectation value of this line operator to leading order in the 't Hooft coupling. The result is a non-trivial function of the mass parameter of the $\mathcal{N}=2^{\ast }$ theory that precisely matches the result from supersymmetric localization.