Hot Jupiter - Cold Jupiter: A complex sibling relation

TL;DR

This study assesses the detectability of distant cold Jupiters in systems with Hot Jupiters using simulations of radial velocity data, revealing observational biases and guiding future survey strategies.

Contribution

It introduces a comprehensive simulation approach to evaluate the detectability of cold Jupiters around Hot Jupiter hosts, highlighting the importance of observational baseline over measurement precision.

Findings

Existing RV data are insensitive to Hot Jupiter-cold Jupiter pairs.

Longer observational baselines improve cold Jupiter detection.

Lower RV measurement precision does not significantly affect detection capability.

Abstract

A handful of planetary systems hosting a Hot Jupiter have been subsequently found to also host long-period giant planets. These ``cold Jupiters,'' giant planets residing beyond the snow line ($\sim$3\,au), play an important role in the dynamical evolution of the system as a whole. In this work, we investigate the detectability of cold Jupiters around a sample of 28 well-studied Hot Jupiter host stars to estimate the occurrence rate of this distinctive system architecture. We perform extensive simulations using the combination of all publicly available radial velocity (RV) data for those stars with synthetic RV data. The synthetic data test observing strategies along three axes: cadence, duration, and measurement precision. For each scenario, we determine detection limits based on the semi-major axis at which a 1 Jupiter mass planet would be recovered 50\% of the time. We find the following: 1) the existing RV data are remarkably insensitive to these Hot Jupiter/Cold Jupiter pairs; 2) the total baseline over which an observational campaign is carried out is the dominant factor in our ability to detect cold Jupiters; and 3) the results are relatively insensitive to the individual RV measurement precision. We conclude that metre-class telescopes with lower RV precision are ideally suited to surveying Hot Jupiter-cold Jupiter systems.