Eclipse timing the Milky Way's gravitational potential

TL;DR

This paper proposes a novel method to measure the Milky Way's gravitational acceleration by detecting tiny shifts in eclipse timings of binary stars over a decade, enabling new insights into Galactic dynamics.

Contribution

It introduces a new approach using eclipse timing variations in Kepler EBs to directly measure Galactic acceleration, considering tidal effects and identifying suitable sources.

Findings

Approximately 70 EBs with sub-second timing precision identified.

A prototype analysis demonstrates the feasibility of measuring Galactic acceleration.

The method can be enhanced with future space missions like JWST and Roman.

Abstract

We show that a small, but \textit{measurable} shift in the eclipse mid-point time of eclipsing binary (EBs) stars of $\sim$ 0.1 seconds over a decade baseline can be used to directly measure the Galactic acceleration of stars in the Milky Way at $\sim$ kpc distances from the Sun. We consider contributions to the period drift rate from dynamical mechanisms other than the Galaxy's gravitational field, and show that the Galactic acceleration can be reliably measured using a sample of $\textit{Kepler}$ EBs with orbital and stellar parameters from the literature. Given the uncertainties on the formulation of tidal decay, our approach here is necessarily approximate, and the contribution from tidal decay is an upper limit assuming the stars are not tidally synchronized. We also use simple analytic relations to search for well-timed sources in the \textit{Kepler} field, and find $\sim$ 70 additional detached EBs with low eccentricities that have estimated timing precision better than 1 second. We illustrate the method with a prototypical, precisely timed EB using an archival \textit{Kepler} light curve and a modern synthetic \textit{HST} light curve (which provides a decade baseline). This novel method establishes a realistic possibility for obtaining fundamental Galactic parameters using eclipse timing to measure Galactic accelerations, along with other emerging new methods, including pulsar timing and extreme precision radial velocity observations. This acceleration signal grows quadratically with time. Therefore, given baselines established in the near-future for distant EBs, we can expect to measure the period drift in the future with space missions like \textit{JWST} and the \textit{Roman Space Telescope}.