Eclipse Timing the Milky Way’s Gravitational Potential

Abstract

We show that a small but measurable shift in the eclipse midpoint time of eclipsing binary (EBs) stars of ∼0.1 s over a decade baseline can be used to directly measure the Galactic acceleration of stars in the Milky Way at ∼kiloparsec 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 Kepler EBs with orbital and stellar parameters from the literature. The contribution from tidal decay we estimate here is an upper limit assuming the stars are not tidally synchronized. We find there are about 200 detached EBs that have estimated timing precision better than 0.5 s, and for which other dynamical effects are subdominant to the Galactic signal. We illustrate the method with a prototypical, precisely timed EB using an archival Kepler light curve and a modern synthetic HST light curve (which provides a decade baseline). This novel method establishes a realistic possibility to constrain dark matter substructure and the Galactic potential 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 JWST and the Roman Space Telescope.

A Noninteracting Galactic Black Hole Candidate in a Binary System with a Main-sequence Star

“…In this section, we speculate that the observed eccentricity of e ∼ 0.4 may have resulted from a possible architecture of a hierarchical triple system. Stellar triples are a common architecture and can affect the dynamical evolution of the system (Tokovinin et al 2006;Tokovinin & Moe 2020;Chakrabarti et al 2022;Lennon et al 2022;Vigna-Gómez et al 2022).…”

Charting Galactic Accelerations with Stellar Streams and Machine Learning

“…Observations of external galaxies have revealed tidal debris, thought to be remnants of accreted satellite galaxies (see, e.g., Kado-Fong et al 2018). For M31 in particular, there is mounting evidence for accreted substructure including the Giant stellar stream and a shelf-feature also indicative of tidal disruption (Ibata et al 2001;Ferguson & Mackey 2016;Conn et al 2016;Chakrabarti et al 2022a). Radial velocities have been measured for a number of stars in the giant stellar stream, and photometric measurements have constrained a distance gradient along the stream (Ibata et al 2014;Conn et al 2016).…”

“…The methods developed in this paper are philosophically similar to recent work that discusses measuring the galactic acceleration field using, e.g., changes in radial velocities over time, pulsar timing arguments, or eclipsing binary star timing arguments (Chakrabarti et al 2020(Chakrabarti et al , 2021(Chakrabarti et al , 2022a. In particular, we rely on changes in the dynamical properties along a stream to estimate accelerations directly.…”

Measuring Galactic Dark Matter through Unsupervised Machine Learning

“…In the real Milky Way galaxy, many of the currently available acceleration measurements assume equilibrium, but there are methods -such as pulsar and binary timing [87,88] -which provide probes of acceleration independent of the Boltzmann Equation. The accuracy and coverage of these techniques will only improve with time.…”