The discovery of three hot Jupiters, NGTS-23b, 24b, and 25b, and updated parameters for HATS-54b from the Next Generation Transit Survey

Abstract

We report the discovery of three new hot Jupiters with the Next Generation Transit Survey (NGTS) as well as updated parameters for HATS-54b, which was independently discovered by NGTS. NGTS-23b, NGTS-24b and NGTS-25b have orbital periods of 4.076, 3.468, and 2.823 days and orbit G-, F- and K-type stars, respectively. NGTS-24 and HATS-54 appear close to transitioning off the main-sequence (if they are not already doing so), and therefore are interesting targets given the observed lack of hot Jupiters around sub-giant stars. By considering the host star luminosities and the planets’ small orbital separations (0.037–0.050 au), we find that all four hot Jupiters are above the minimum irradiance threshold for inflation mechanisms to be effective. NGTS-23b has a mass of 0.61 MJ and radius of 1.27 RJ and is likely inflated. With a radius of 1.21 RJ and mass of 0.52 MJ, NGTS-24b has a radius larger than expected from non-inflated models but its radius is smaller than the predicted radius from current Bayesian inflationary models. Finally, NGTS-25b is intermediate between the inflated and non-inflated cases, having a mass of 0.64 MJ and a radius of 1.02 RJ. The physical processes driving radius inflation remain poorly understood, and by building the sample of hot Jupiters we can aim to identify the additional controlling parameters, such as metallicity and stellar age.

Planet Hunters NGTS: New Planet Candidates from a Citizen Science Search of the Next Generation Transit Survey Public Data

“…For context, we describe the internal vetting process that has been used in the discovery of 23 exoplanets to date by NGTS (Bayliss et al 2018;Günther et al 2018;Raynard et al 2018;Eigmüller et al 2019;Vines et al 2019;West et al 2019;Bryant et al 2020;Costes et al 2020;McCormac et al 2020;Grieves et al 2021;Smith et al 2021;Tilbrook et al 2021;Alves et al 2022;Jackson et al 2023;F. Bouchy et al 2024, in preparation).…”

“…PHNGTS uses data from the Next Generation Transit Survey (NGTS; Wheatley et al 2018; see Section 2), that has been surveying large sections of the sky in search of exoplanet transits since 2015. To date, the facility has discovered tens of exoplanets (e.g., Bayliss et al 2018;Tilbrook et al 2021;Jackson et al 2023) primarily through the visual vetting of candidates identified by ORION, a custom BLS algorithm adapted from Collier . While the primary objective of the Planet Hunters and Planet Hunters TESS projects is to identify transit events that were not detected by the standard detection pipelines, PHNGTS uses phase-folded light curves from the ORION algorithm with the aim being to classify transit-like events in the NGTS data and identify planet candidates that were missed in the initial vetting of these data.…”

Statistical Signatures of Nanoflare Activity. III. Evidence of Enhanced Nanoflaring Rates in Fully Convective stars as Observed by the NGTS

“…The average standard deviation of the time series across the full sample was 2.0% ± 0.8% of the mean, thus an equivalent fluctuation profile can be applied to the modeling. Next, in a similar manner to Jackson et al (2023), complementary photometric and astrometric data from Gaia Data Release 3 (Gaia Collaboration et al 2016 were utilized to exclude unwanted candidates from the sample. In particular, astrometric excess noise analysis was applied to exclude any binary systems (Evans 2018), and the photometric filtering processes of Arenou et al (2018) identified any blended sources.…”