Reply to Comment on "Gravitational Waves From Ultra- Short Period Exoplanets"

TL;DR

This paper defends the feasibility of detecting gravitational waves from ultra-short period exoplanets with LISA, arguing that their population could be large enough for future observations to surpass previous criticisms.

Contribution

It clarifies limitations in prior criticism and emphasizes the potential for LISA to detect gravitational waves from a significant population of ultra-short period exoplanets.

Findings

A sphere of 250 pc could contain ~10^4 ultra-short period exoplanets.

These exoplanets could produce characteristic strains detectable by LISA.

Future data may confirm the detectability of such gravitational waves.

Abstract

Wong et al. (2018) recently performed an encouraging criticism to our paper "Gravitational waves from ultra-short period exoplanets" (Cunha, Silva, Lima 2018) exploring the potentialities of a subset of exoplanets with extremely short periods (less than 80 min) as a possible scientific target to the planned space-based LISA observatory. Here we call attention to some subtleties and limitations underlying the basic criticism which in our view were not properly stressed in their comment. Particularly, simple estimates show that a sphere encircling the Earth with a radius of 250 pc may accommodate a population $ \sim 10^{4}$ ultra-short period exoplanets with characteristic strain of the same order or higher than the ones analyzed in our paper. This means that the question related to the gravitational wave pattern of ultra-short period exoplanets may be surpassed near future by the LISA instrument with new and more definitive data.