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

Abstract

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 $2<R_{\mathrm{p}}<20R_{\oplus }$, the occurrence rates are $12.1_{-2.3}^{+3.0}$, $10.2_{-1.0}^{+1.2}$, and $13.1_{-1.2}^{+1.4}$ planets per 100 stars for F-, G-, and K-type hosts, consistent with each other at $1\sigma$, so any spectral-type dependence is localized rather than global. For transiting hot Jupiters, we measure $0.30_{-0.03}^{+0.04}$, $0.50\pm 0.03$, and $0.67_{-0.07}^{+0.08}$ 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 $0.069_{-0.011}^{+0.045}$, $0.093_{-0.022}^{+0.046}$, and $0.150_{-0.026}^{+0.033}$ 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 $6$-$8R_{\oplus }$ strip indicates that a distinct Neptunian ridge is not required to explain the measurements.

arXiv comment21 pages, 17 figures, 10 tables, accepted for publication in MNRAS. Online interactive TESS occurrence rate: https://cuikaiming.com/TESS-SPOC-Occurrence-Rate/#fgk