WASP-South detection of HD219666b transits provides an accurate ephemeris

TL;DR

This paper reports the recovery of the transit of HD219666b using WASP-South data, significantly improving the ephemeris accuracy for future atmospheric studies with major telescopes.

Contribution

It provides an improved, highly precise ephemeris for HD219666b by analyzing 8 years of data, aiding future observational efforts.

Findings

Transit of HD219666b successfully recovered in WASP-South data.

Ephemeris uncertainty reduced by a factor of 60.

Enables precise scheduling for atmospheric characterization.

Abstract

The hot-Neptune HD219666b (= TOI-118.01) was an early discovery from Sector 1 of the TESS transit survey. Being a rare "Neptune desert" planet, and transiting a bright, V = 9.9 star, it is a prime target for further study including atmospheric characterisation. Targeting exoplanet transits with major facilities such as HST and the imminent JWST depends on an accurate ephemeris. Here we report a recovery of the transit in WASP-South data, enabling an ephemeris from data spanning 8 years that has a period uncertainty which is smaller by a factor 60 compared to the discovery paper.