Description:

Speaker: Yael Alush, Hebrew University of Jerusalem

Title: Testing the No-Hair Theorem on Sgr A*- Revisited

Abstract: The "no-hair" theorem can, in principle, be tested at the center of the Milky Way by measuring the spin and the quadrupole moment of Sgr A* with the orbital precession of S-stars, measured over their full periods. Contrary to the original method, I will show why it is possible to test the no-hair theorem using observations from only a single star, by measuring precession angles over a half-orbit. Also, I will show that a judicious choice of measurable precession angles can often eliminate individual astrophysical noise sources that may impede future quadrupole measurements. In particular, I will focus on the large noise source of mass precession, the novel noise of spin-curvature coupling due to stellar spin, and the more complicated noise source arising from transient quadrupole moments in the stellar potential.