Predictions for the fragment masses compatible with production via gravitational instability for HIP 64892. Fragments with masses above the orange dashed line cannot cool efficiently enough, while those below the blue solid line do not satisfy the Toomre criterion. The mass and projected separation of HIP 64892B are marked. We find that HIP 64892B is compatible with in situ formation via gravitational instability, although further constraints on the semi-major axis are needed to confirm this idea. The initial disk masses required to form fragments of a given size are shown with black dotted lines.