An upper limit on the spin of SgrA$^*$ based on stellar orbits in its vicinity

TL;DR

This study constrains the spin of the Milky Way's central black hole, SgrA*, by analyzing stellar orbits, establishing an upper limit of approximately 0.1 based on the lack of observed frame-dragging precession.

Contribution

It provides the first upper limit on SgrA*'s spin using stellar orbit data and frame-dragging considerations.

Findings

Upper limit on SgrA*'s spin: χ ≲ 0.1

Stellar orbit distribution constrains black hole spin

Frame-dragging precession timescale used for constraint

Abstract

The spin of the massive black hole (BH) at the center of the Milky Way, SgrA$^*$, has been poorly constrained so far. We place an upper limit on the spin of SgrA$^*$ based on the spatial distribution of the S-stars, which are arranged in two almost edge-on disks that are located at a position angle approximately $\pm 45^\circ$ with respect to the Galactic plane, on a milliparsec scale around the Galactic Center. Requiring that the frame-dragging precession has not had enough time to make the S-star orbital angular momentum precess, the spin of the massive BH at the center of the Milky Way can be constrained to $\chi\lesssim 0.1$.