On the possibility of detecting ultra-short period exoplanets with LISA

TL;DR

This paper evaluates the potential for LISA to detect gravitational waves from ultra-short period exoplanets, concluding current known systems are unlikely detectable but emphasizing the scientific interest of such future detections.

Contribution

The study revisits previous claims and provides a more cautious assessment of LISA's ability to detect gravitational waves from known exoplanets, highlighting the need for better system data and modeling.

Findings

Current known exoplanets are unlikely detectable by LISA.

Detection depends on improved knowledge of exoplanet properties.

Further research is needed to assess LISA's potential for exoplanet detection.

Abstract

Cunha et al. (2018) recently reexamined the possibility of detecting gravitational waves from exoplanets, claiming that three ultra-short period systems would be observable by LISA. We revisit their analysis and conclude that the currently known exoplanetary systems are unlikely to be detectable, even assuming a LISA observation time $T_{\rm obs}=4$ yrs. Conclusive statements on the detectability of one of these systems, GP Com b, will require better knowledge of the system's properties, as well as more careful modeling of both LISA's response and the galactic confusion noise. Still, the possibility of exoplanet detection with LISA is interesting enough to warrant further study, as gravitational waves could yield dynamical properties that are difficult to constrain with electromagnetic observations.