NGTS-14Ab: a Neptune-sized transiting planet in the desert

TL;DR

This paper reports the discovery and characterization of NGTS-14Ab, a Neptune-sized planet within the Neptunian desert, using combined photometric and radial velocity data, and discusses its implications for planetary formation.

Contribution

The study presents the first detailed analysis of a Neptune-sized planet in the Neptunian desert, including its system parameters and potential stellar companion, expanding understanding of this planetary population.

Findings

NGTS-14Ab has a radius 30% larger than Neptune.

NGTS-14Ab has a mass 70% greater than Neptune.

The planet orbits a K1 star every 3.54 days.

Abstract

Context: The sub-Jovian or Neptunian desert is a previously-identified region of parameter space where there is a relative dearth of intermediate-mass planets at short orbital periods. Aims: We present the discovery of a new transiting planetary system within the Neptunian desert, NGTS-14. Methods: Transits of NGTS-14Ab were discovered in photometry from the Next Generation Transit Survey (NGTS). Follow-up transit photometry was conducted from several ground-based facilities, as well as extracted from TESS full-frame images. We combine radial velocities from the HARPS spectrograph with the photometry in a global analysis to determine the system parameters. Results: NGTS-14Ab has a radius about 30 per cent larger than that of Neptune ($0.444\pm0.030~\mathrm{R_{Jup}}$), and is around 70 per cent more massive than Neptune ($0.092 \pm 0.012~\mathrm{M_{Jup}}$). It transits the main-sequence K1 star, NGTS-14A, with a period of 3.54 days, just far enough to have maintained at least some of its primordial atmosphere. We have also identified a possible long-period stellar mass companion to the system, NGTS-14B, and we investigate the binarity of exoplanet host stars inside and outside the Neptunian desert using Gaia.