Distance Estimation and Sky Localization of Eccentric Double White Dwarf Binaries from Gravitational Wave Observations inside Globular Clusters

TL;DR

This study demonstrates that gravitational wave observations of eccentric double white dwarf binaries can provide highly precise distance and sky localization estimates, surpassing current methods, especially for binaries in dense environments like globular clusters.

Contribution

The paper introduces a method to estimate distances and sky locations of eccentric DWDs from GW signals, highlighting improved precision over existing techniques and applicability to dense stellar environments.

Findings

Distances can be estimated with higher precision than current methods.

Higher eccentricity increases the accuracy of distance and localization estimates.

At least a few eccentric DWDs are expected to be detectable in globular clusters.

Abstract

The cosmic distance scale is built on multiple different techniques for estimating distances in space that are often connected and dependent on multiple measurements and assumptions. Double white dwarf binaries (DWDs) are common objects and are expected to produce gravitational wave (GW) signals that can be observed with space-based detectors such as LISA. By analyzing these signals we should be able to estimate the distance and sky location of the source. Previous studies have done this for circular binaries which, while they are abundant, have, in general, weaker signals than eccentric binaries and it is not possible to differentiate whether a circular binary is in the field or in a dense environment such as a globular cluster (GC). In this paper we used eccentric binaries from MOCCA GC simulations, simulated the GW signal from each binary at locations related to GCs in the Milky Way and estimated the precision on the distance and the sky location of the source. We find that distances can be estimated with higher precision than current day methods even with low eccentricity binaries and higher eccentricity further increases this precision. Although the probability of finding a tight and eccentric DWD is far lower than a circular one, we can expect to find at least a few in the dense environments of the Milky Way, such as GCs. These estimations would be independent measurements with high precision to objects inside dense environments, such as GCs inside the Milky Way and the Magellanic Clouds.