The period-index problem for hyper-K\'ahler varieties via hyperholomorphic bundles

We prove new bounds for the period-index problem for hyper-K\"ahler varieties of $K3^{[n]}$-type using projectively hyperholomorphic bundles constructed by Markman. We show that $\mathrm{dim}(X)$ is a bound for any $X$ of $K3^{[n]}$-type. We also show that the bound can be reduced to $\frac{1}{2}\mathrm{dim}(X)$, as conjectured by Huybrechts, when the Picard rank of $X$ is at least 3.
Comment: 18 pages. Comments welcome