Understanding Fomalhaut as a Cooper pair

TL;DR

This paper investigates the gravitational relationship of the Fomalhaut system, proposing that Fomalhaut C is a gravitational pair with A and B, similar to Cooper pairs in superconductors, based on new data and simulations.

Contribution

It introduces the concept of Fomalhaut C as a gravitational pair, applying a Bayesian framework and environmental energy considerations to stellar system stability.

Findings

Fomalhaut C is likely a gravitational pair with A and B.

An upper velocity difference limit of 8 km/s for binary candidates.

An empirical escape radius formula improves stability measurement of wide binaries.

Abstract

Fomalhaut is a nearby stellar system and has been found to be a triple based on astrometric observations. With new radial velocity and astrometric data, we study the association between Fomalhaut A, B, and C in a Bayesian framework finding that the system is gravitationally bound or at least associated. Based on simulations of the system, we find that Fomalhaut C can be easily destabilized through combined perturbations from the Galactic tide and stellar encounters. Considering that observing the disruption of a triple is probably rare in the solar neighbourhood, we conclude that Fomalhaut C is a so-called "gravitational pair" of Fomalhaut A and B. Like the Cooper pair mechanism in superconductors, this phenomena only appears once the orbital energy of a component becomes comparable with the energy fluctuations caused by the environment. Based on our simulations we find (1) an upper limit of 8 km/s velocity difference is appropriate when selecting binary candidates and (2) an empirical formula for the escape radius, which is more appropriate than tidal radius when measuring the stability of wide binaries.