Deviation of Stellar Orbits from Test Particle Trajectories Around Sgr A* Due to Tides and Winds

TL;DR

This paper examines how stellar winds and tidal effects influence the orbits of stars around Sgr A*, highlighting that tidal dissipation could affect measurements of black hole properties such as spin and quadrupole moment.

Contribution

It provides an analysis of non-conservative effects on stellar orbits, emphasizing the potential impact of tidal dissipation on testing the no-hair theorem.

Findings

Stellar winds are generally negligible in affecting stellar orbits.

Tidal dissipation can occur on timescales comparable to orbital precession for highly eccentric orbits.

Tidal effects may introduce systematic uncertainties in black hole parameter measurements.

Abstract

Monitoring the orbits of stars around Sgr A* offers the possibility of detecting the precession of their orbital planes due to frame dragging, of measuring the spin and quadrupole moment of the black hole, and of testing the no-hair theorem. Here we investigate whether the deviations of stellar orbits from test-particle trajectories due to wind mass loss and tidal dissipation of the orbital energy compromise such measurements. We find that the effects of stellar winds are, in general, negligible. On the other hand, for the most eccentric orbits (e>0.96) for which an optical interferometer, such as GRAVITY, will detect orbital plane precession due to frame dragging, the tidal dissipation of orbital energy occurs at timescales comparable to the timescale of precession due to the quadrupole moment of the black hole. As a result, this non-conservative effect is a potential source of systematic uncertainty in testing the no-hair theorem with stellar orbits.