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

¹ Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany
e-mail: alexis.smith@dlr.de
² School of Physics and Astronomy, University of Leicester, LE1 7RH, UK
³ Centre for Exoplanets and Habitability, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁴ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁵ Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland
⁶ Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Av.Diagonal las Torres 2640, Peñalolén, Santiago, Chile
⁷ Millennium Institute for Astrophysics, Santiago, Chile
⁸ Astrophysics Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
⁹ Center for Astronomy and Astrophysics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
¹⁰ Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, BT7 1NN Belfast, UK
¹¹ Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS, UK
¹² Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Mass. Ave, Cambridge, MA 02139, USA
¹³ Instituto de Astronomía, Universidad Católica del Norte, Angamos 0610, 1270709 Antofagasta, Chile
¹⁴ Institute of Geological Sciences, FU Berlin, Malteserstr. 74-100, 12249 Berlin, Germany
¹⁵ Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile

Received: 19 October 2020
Accepted: 5 January 2020

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 with 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 that is about 30 per cent larger than that of Neptune (0.444 ± 0.030 R_Jup) and is around 70 per cent more massive than Neptune (0.092 ± 0.012 M_Jup). It transits the main-sequence K1 star, NGTS-14A, with a period of 3.54 days, just far away 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.