Phantom Inflated Planets in Occurrence Rate Based Samples

TL;DR

This paper identifies a bias in exoplanet occurrence rate samples caused by inflated giant planet radii that do not account for temperature-dependent inflation, leading to overestimations of detectable planets.

Contribution

It highlights the presence of phantom inflated planets in predicted exoplanet samples and emphasizes the need to consider temperature effects in radius estimates for accurate occurrence rates.

Findings

Inflated planets constitute over 1.1% of Sullivan et al. (2015) sample.

Inflated planets make up about 8% of Barclay et al. (2018) sample.

Ignoring temperature dependence leads to overestimating planet detectability.

Abstract

The recently launched Transiting Exoplanet Survey Satellite (TESS) is expected to produce many new exoplanet discoveries which will be especially amenable to follow-up study. Assessments of the planet discovery yield of TESS, such as Sullivan et al. (2015) and Barclay et al. (2018), will be important for planning follow-up work. Analyzing these predicted planet samples, however, we find that giant planet radii derived from the current bulk transiting planet sample have been used at all potential orbits without accounting for the temperature dependence of radius inflation. These phantom inflated planets (PIPs) make up just over 1.1% of the Sullivan et al. (2015) predicted population and about 8% of the Barclay et al. (2018) sample. Similar population predictions for direct imaging studies should likewise take care not to include inflated planets at large separations as such planets will appear larger and, depending on assumed albedo, brighter and more easily detectable than physically possible. Despite their high false positive rate, giant planets are the testbeds for atmospheric characterization techniques and care should be taken to understand and account for potential contaminating factors in this population.