Demographics of Close-In TESS Exoplanets Orbiting FGK Main-sequence Stars – II. Spectral-Type Dependence and the Neptunian Landscape

Understanding how planetary demographics depend on host star properties is essential for constraining planet formation and evolution theories. In this paper, we analyse close-in (0.5–16 d) planet occurrence rates from the TESS Science Processing Operations Center (SPOC) full-frame image data for individual F-, G-, and K-type main-sequence stellar samples. Integrated over 0.5 < P < 16 d and 2 < Rp < 20 R⊕, the occurrence rates are 12.1+3.0-2.3, 10.2+1.2-1.0, and 13.1+1.4-1.2 planets per 100 stars for F-, G-, and K-type hosts, consistent with each other at 1σ, so any spectral-type dependence is localized rather than global. For transiting hot Jupiters, we measure 0.30+0.04-0.03, 0.50 ± 0.03, and 0.67+0.08-0.07 per cent, with the rate peaking at K type; the latter being the first such measurement for K-type hosts. Modelling the Neptunian desert directly in occurrence-rate space, we find that the desert extends to longer orbital periods around hotter stars. Integrating over the desert interior gives 0.069+0.045-0.011, 0.093+0.046-0.022, and 0.150+0.033-0.026 planets per 100 stars, implying about one close-in planet in a hundred lies inside the desert, and the desert is roughly twice as populated around K- as around F-type hosts. A rigorous Bayesian model comparison for the 6–8 R⊕ strip indicates that a distinct Neptunian ridge is not required to explain the measurements.