NGTS-4b: A sub-Neptune Transiting in the Desert

2018/09/03 by Richard G. West, R. G. West, Edward Gillen +78 · 1 voice · 4 citations
Physics and Astronomy · #Astro and Planetary Science #Astronomy and Astrophysical Research #Stellar, planetary, and galactic studies #astro-ph.EP

paper · pdf · doi:10.1093/mnras/stz1084

Submitted to MNRAS

arxiv created 2018/09/03 · openalex publication_date 2019/04/18 · arxiv updated 2019/05/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29

Abstract

We report the discovery of NGTS-4b, a sub-Neptune-sized planet transiting a 13th magnitude K-dwarf in a 1.34d orbit. NGTS-4b has a mass M=20.6±3.0M_E and radius R=3.18±0.26R_E, which places it well within the so-called "Neptunian Desert". The mean density of the planet (3.45±0.95g/cm³) is consistent with a composition of 100% H₂O or a rocky core with a volatile envelope. NGTS-4b is likely to suffer significant mass loss due to relatively strong EUV/X-ray irradiation. Its survival in the Neptunian desert may be due to an unusually high core mass, or it may have avoided the most intense X-ray irradiation by migrating after the initial activity of its host star had subsided. With a transit depth of 0.13±0.02%, NGTS-4b represents the shallowest transiting system ever discovered from the ground, and is the smallest planet discovered in a wide-field ground-based photometric survey.

Citations

• Astrophysics Source Code Library
• THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE): MISSION DESCRIPTION AND INITIAL ON-ORBIT PERFORMANCE
• The Two Micron All Sky Survey (2MASS)
• DAOPHOT - A computer program for crowded-field stellar photometry
• MESA ISOCHRONES AND STELLAR TRACKS (MIST) 0: METHODS FOR THE CONSTRUCTION OF STELLAR ISOCHRONES
• A giant planet undergoing extreme-ultraviolet irradiation by its hot massive-star host

Cited by

• SPECULOOS: five years hunting terrestrial planets around ultra-cool dwarfs
• NGTS-14Ab: a Neptune-sized transiting planet in the desert
• NGTS-12b: A sub-Saturn mass transiting exoplanet in a 7.53 day orbit
• Implications of an improved water equation of state for water-rich planets

Discussions

• The 'forbidden' planet has been found in the 'Neptunian Desert' [hn, 2 points, 0 comments]

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