Search

We present the discoveries of NGTS-31b(= TOI-2721), and NGTS-32b, two hot Jupiters from the Next Generation Transit Survey (NGTS) transiting slightly evolved stars. The orbital periods, radii, and masses are 4.16 and 3.31 d, 1.61 and 1.42 |$R_{J}$|⁠ , and 1.12 and 0.57 |$M_{J}$|⁠ , respectively. Both planets have an incident stellar flux significantly above the threshold where inflation occurs, with both planets showing signs of inflation. These planets have widely different equilibrium temperatures than other hot Jupiters of similar mass and radius, with NGTS-31b having a significantly lower temperature, and NGTS-32b being hotter. This dichotomy raises the question of how prevalent the roles of other inflation mechanisms are in the radius anomaly phenomena and will help further constrain different inflationary models. [ABSTRACT FROM AUTHOR]

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 d 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 M J and radius of 1.27  R J and is likely inflated. With a radius of 1.21  R J and mass of 0.52 M J, 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 M J and a radius of 1.02  R J. 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. [ABSTRACT FROM AUTHOR]

We report the discovery of four new hot Jupiters with the Next-Generation Transit Survey (NGTS). NGTS-15b, NGTS-16b, NGTS-17b, and NGTS-18b are short-period (P < 5 d) planets orbiting G-type main-sequence stars, with radii and masses between 1.10 and 1.30 R J and 0.41 and 0.76 M J, respectively. By considering the host star luminosities and the planets' small orbital separations (0.039–0.052 au), we find that all four hot Jupiters are highly irradiated and therefore occupy a region of parameter space in which planetary inflation mechanisms become effective. Comparison with statistical studies and a consideration of the planets' high incident fluxes reveal that NGTS-16b, NGTS-17b, and NGTS-18b are indeed likely inflated, although some disparities arise upon analysis with current Bayesian inflationary models. However, the underlying relationships that govern radius inflation remain poorly understood. We postulate that the inclusion of additional hyperparameters to describe latent factors such as heavy element fraction, as well as the addition of an updated catalogue of hot Jupiters, would refine inflationary models, thus furthering our understanding of the physical processes that give rise to inflated planets. [ABSTRACT FROM AUTHOR]

We report the discovery of the transiting exoplanet NGTS-12b by the Next Generation Transit Survey (NGTS). The host star, NGTS-12, is a V = 12.38 mag star with an effective temperature of Teff = 5690 ± 130 K. NGTS-12b orbits with a period of P  = 7.53 d, making it the longest period planet discovered to date by the main NGTS survey. We verify the NGTS transit signal with data extracted from the Transiting Exoplanet Survey Satellite (TESS) full-frame images, and combining the photometry with radial velocity measurements from HARPS and FEROS we determine NGTS-12b to have a mass of 0.208 ± 0.022 M J and a radius of 1.048 ± 0.032 R J . NGTS-12b sits on the edge of the Neptunian desert when we take the stellar properties into account, highlighting the importance of considering both the planet and star when studying the desert. The long period of NGTS-12b combined with its low density of just 0.223 ± 0.029 g cm−3 make it an attractive target for atmospheric characterization through transmission spectroscopy with a Transmission Spectroscopy Metric of 89.4. [ABSTRACT FROM AUTHOR]

We report the period, eccentricity, and mass determination for the Transiting Exoplanet Survey Satellite (TESS) single-transit event candidate TOI-222, which displayed a single 3000 ppm transit in the TESS 2-min cadence data from Sector 2. We determine the orbital period via radial velocity measurements (P = 33.9 d), which allowed for ground-based photometric detection of two subsequent transits. Our data show that the companion to TOI-222 is a low-mass star, with a radius of |$0.18_{-0.10}^{+0.39}$|  R⊙ and a mass of 0.23 ± 0.01 M⊙. This discovery showcases the ability to efficiently discover long-period systems from TESS single-transit events using a combination of radial velocity monitoring coupled with high-precision ground-based photometry. [ABSTRACT FROM AUTHOR]

We report the discovery, by the next generation transit survey (NGTS), of two hot Jupiters NGTS-8b and NGTS-9b. These orbit a |$V\, =\, 13.68$| K0V star (T eff  =  5241 ± 50 K) with a period of 2.49970 d, and a |$V\, =\, 12.80$| F8V star (T eff  =  6330 ± 130 K) in 4.43527 d, respectively. The transits were independently verified by follow-up photometric observations with the South African Astronomical Observatory 1.0-m and Euler telescopes, and we report on the planetary parameters using HARPS, FEROS, and CORALIE radial velocities. NGTS-8b has a mass, |$0.93\, ^{+0.04}_{-0.03}$|  MJ and a radius, 1.09 ± 0.03 RJ similar to Jupiter, resulting in a density of |$0.89\, ^{+0.08}_{-0.07}$|  g cm−3. This is in contrast to NGTS-9b, which has a mass of 2.90 ± 0.17 MJ and a radius of 1.07 ± 0.06 RJ, resulting in a much greater density of |$2.93^{+0.53}_{-0.49}$|  g cm−3. Statistically, the planetary parameters put both objects in the regime where they would be expected to exhibit larger than predicted radii. However, we find that their radii are in agreement with predictions by theoretical non-inflated models. [ABSTRACT FROM AUTHOR]

We report the discovery of a new ultrashort period hot Jupiter from the Next Generation Transit Survey. NGTS-6b orbits its star with a period of 21.17 h, and has a mass and radius of |$1.330^{+0.024}_{-0.028}$| M J and |$1.271^{+0.197}_{-0.188}$| R J, respectively, returning a planetary bulk density of |$0.711^{+0.214}_{-0.136}$|  g cm−3. Conforming to the currently known small population of ultrashort period hot Jupiters, the planet appears to orbit a metal-rich star ([Fe/H] = +0.11 ± 0.09 dex). Photoevaporation models suggest the planet should have lost 5 per cent of its gaseous atmosphere over the course of the 9.6 Gyr of evolution of the system. NGTS-6b adds to the small, but growing list of ultrashort period gas giant planets, and will help us to understand the dominant formation and evolutionary mechanisms that govern this population. [ABSTRACT FROM AUTHOR]