# Listening to dark sirens from gravitational waves:\it{Combined effects of fifth force, ultralight particle radiation, and eccentricity}

## TL;DR

This paper derives constraints on fifth forces, ultralight particles, and alternative gravity theories from gravitational wave observations and orbital decay in binary systems, enhancing understanding of fundamental physics beyond General Relativity.

## Contribution

It provides detailed analytical derivations of orbital period loss considering multiple effects and sets new bounds on fifth force strength, ultralight particle couplings, and scalar-tensor theories using observational data.

## Key findings

- Constraints on fifth force strength: -3 to -2 range.
- Limits on ultralight scalar and vector particle couplings: -20 scale.
- Bounds on Brans-Dicke parameter: 2 to 5 range.

## Abstract

We derive in detail the orbital period loss of a compact binary system in presence of a fifth force and radiation of ultralight particles for a general eccentric Keplerian orbit. We obtain constraints on fifth force strength $\alpha\lesssim 1.11\times 10^{-3}$ from the orbital period decay of compact binary systems. We derive constraints on the gauge coupling of ultralight scalar $(g_S\lesssim 3.06\times 10^{-20})$ and vector $(g_V\lesssim 2.29\times 10^{-20})$ particles from orbital period loss and the constraints get stronger in presence of a fifth force $(\alpha=0.9)$. In addition, we also obtain constraints on the axion decay constant $(7.94\times 10^{10}~\rm{GeV}\lesssim f_a\lesssim 3.16\times 10^{17}~\rm{GeV}, \alpha=0.9)$ if the orbital period decays due to the combined effects of axionic fifth force and axion radiation. We also achieve constraints on the strengths of the fifth force $(\alpha\lesssim 0.025)$ and radiation $(\beta\lesssim 10^{-3})$ from GW170817. The constraints on new force parameters depend on the choice of the initial eccentricity which we include in our analysis $(\epsilon_0=10^{-6}, 0.1)$. We do the model independent estimate of the capture of dark matter mass fraction by a binary system. Lastly, we obtain constraints on fifth force strength due to Brans-Dicke mediated scalar between two compact stars in a binary system $(\omega_{\rm{BD}}>266)$ and from the Nordtvedt effect $(\omega_{\rm{BD}}>75858)$. The bound on Brans-Dicke coupling gets stronger if one includes the effect of eccentricity. Our constraints can be generalized to any alternative theories of gravity and will be within the reach of second and third generation gravitational wave detectors.