NGTS-33b: A Young Super-Jupiter Hosted by a Fast Rotating Massive Hot Star

TL;DR

This paper reports the discovery of NGTS-33b, a young, massive hot Jupiter orbiting a fast-rotating hot star, providing new insights into the properties and evolution of such planetary systems.

Contribution

The discovery of NGTS-33b around a young, hot, fast-rotating star offers valuable data on young super-Jupiters and their atmospheric characteristics, expanding current understanding of planetary formation.

Findings

NGTS-33b is a young super-Jupiter with 3.6 Mjup, 1.64 Rjup, orbiting a 20-50 Myr old star.

The host star is a fast rotator with a period of 0.6654 days and a temperature of 7437 K.

NGTS-33b has a low bulk density and an atmosphere possibly up to 15% inflated.

Abstract

In the last few decades planet search surveys have been focusing on solar type stars, and only recently the high-mass regimes. This is mostly due to challenges arising from the lack of instrumental precision, and more importantly, the inherent active nature of fast rotating massive stars. Here we report NGTS-33b (TOI-6442b), a super-Jupiter planet with mass, radius and orbital period of 3.6 $\pm$ 0.3 M$_{\rm jup}$, 1.64 $\pm$ 0.07 R$_{\rm jup}$ and $2.827972 \pm 0.000001$ days, respectively. The host is a fast rotating ($0.6654 \pm 0.0006$ day) and hot (T$_{\rm eff}$ = 7437 $\pm$ 72 K) A9V type star, with a mass and radius of 1.60 $\pm$ 0.11 M$_{\odot}$ and 1.47 $\pm$ 0.06 R$_{\odot}$, respectively. Planet structure and Gyrochronology models shows that NGTS-33 is also very young with age limits of 10-50 Myr. In addition, membership analysis points towards the star being part of the Vela OB2 association, which has an age of $\sim$ 20-35 Myr, thus providing further evidences about the young nature of NGTS-33. Its low bulk density of 0.19$\pm$0.03 g cm$^{-3}$ is 13$\%$ smaller than expected when compared to transiting hot Jupiters with similar masses. Such cannot be solely explained by its age, where an up to 15$\%$ inflated atmosphere is expected from planet structure models. Finally, we found that its emission spectroscopy metric is similar to JWST community targets, making the planet an interesting target for atmospheric follow-up. Therefore, NGTS-33b's discovery will not only add to the scarce population of young, massive and hot Jupiters, but will also help place further strong constraints on current formation and evolution models for such planetary systems.