TOI-824 b: A New Planet on the Lower Edge of the Hot Neptune Desert

TL;DR

This paper reports the discovery and confirmation of TOI-824 b, a hot Neptune exoplanet with a dense atmosphere, orbiting a nearby star, and highlights its potential for atmospheric characterization due to its high temperature and cloud-free conditions.

Contribution

The paper presents the discovery of a new hot Neptune exoplanet on the lower edge of the hot Neptune desert, with detailed mass, radius, and density measurements, and discusses its suitability for atmospheric studies.

Findings

Planet has a radius of 2.93 R⊕ and mass of 18.47 M⊕.

Density is more than twice that of Neptune, at 4.03 g/cm³.

High equilibrium temperature suggests a cloud-free atmosphere, ideal for follow-up observations.

Abstract

We report the detection of a transiting hot Neptune exoplanet orbiting TOI-824 (SCR J1448-5735), a nearby (d = 64 pc) K4V star, using data from the \textit{Transiting Exoplanet Survey Satellite} (TESS). The newly discovered planet has a radius, $R_{\rm{p}}$ = 2.93 $\pm$ 0.20 R$_{\oplus}$, and an orbital period of 1.393 days. Radial velocity measurements using the Planet Finder Spectrograph (PFS) and the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph confirm the existence of the planet and we estimate its mass to be $M_{\rm{p}}$ = 18.47 $\pm$ 1.84 M$_{\oplus}$. The planet's mean density is $\rho_{\rm{p}}$ = 4.03$^{+0.98}_{-0.78}$ g cm$^{-3}$ making it more than twice as dense as Neptune. TOI-824 b's high equilibrium temperature makes the planet likely to have a cloud free atmosphere, and thus an excellent candidate for follow up atmospheric studies. The detectability of TOI-824 b's atmosphere from both ground and space is promising and could lead to the detailed characterization of the most irradiated, small planet at the edge of the hot Neptune desert that has retained its atmosphere to date.