Extracting Astrophysical Information of Highly-Eccentric Binaries in the Millihertz Gravitational Wave Band

TL;DR

This paper demonstrates that detecting millihertz gravitational waves from highly eccentric binaries can precisely determine their orbital parameters, offering insights into their evolution and formation, despite some degeneracies in other parameters.

Contribution

It introduces a method to extract detailed orbital information of highly eccentric binaries from GW signals, improving parameter estimation accuracy in the mHz band.

Findings

Relative error of ~10^{-6} in orbital frequency

Eccentricity can be measured within ~1%

Highly eccentric systems can be efficiently identified in LISA data

Abstract

Wide, highly eccentric ($e>0.9$) compact binaries can naturally arise as progenitors of gravitational wave (GW) mergers. These systems are expected to have a significant population in the mHz band (e.g., $\sim 3-45$ detectable stellar-mass binary black holes with $e>0.9$ in the Milky Way), with their GW signals characterized by "repeated bursts" emitted upon each pericenter passage. In this study, we show that the detection of mHz GW signals from highly eccentric stellar mass binaries in the local universe can strongly constrain their orbital parameters. Specifically, it can achieve a relative measurement error of $\sim 10^{-6}$ for orbital frequency and $\sim 1\%$ for eccentricity (as $1-e$) in most of the detectable cases. On the other hand, the binary's mass ratio, distance, and intrinsic orbital orientation may be less precisely determined due to degeneracies in the GW waveform. We also perform mock LISA data analysis to evaluate the realistic detectability of highly eccentric compact binaries. Our results show that highly eccentric systems could be efficiently identified when multiple GW sources and stationary Gaussian instrumental noise are present in the detector output. This work highlights the potential of extracting the signal of "bursting'' LISA sources to provide valuable insights into their orbital evolution, surrounding environment, and formation channels.