Source integrals for multipole moments in static and axially symmetric spacetimes

Abstract

In this article, we derive source integrals for multipole moments in axially symmetric and static spacetimes. The multipole moments can be read off the asymptotics of the metric close to spatial infinity in a hypersurface, which is orthogonal to the timelike Killing vector. Whereas for the evaluation of the source integrals the geometry needs to be known in a compact region of this hypersurface, which encloses all source, i.e. matter as well as singularities. The source integrals can be written either as volume integrals over such a region or in quasi-local form as integrals over the surface of that region.