Abstract: We report the discovery of a 1.32(-0.10)(+0.10)M(Jup) planet orbiting on a 75.12 day period around the G3V 10.8(-3.6)(+2.1) Gyr old star TOI-5542 (TIC 466206508; TYC 9086-1210-1). The planet was first detected by the Transiting Exoplanet Survey Satellite (TESS) as a single transit event in TESS Sector 13. A second transit was observed 376 days later in TESS Sector 27. The planetary nature of the object has been confirmed by ground-based spectroscopic and radial velocity observations from the CORALIE and HARPS spectrographs. A third transit event was detected by the ground-based facilities NGTS, EulerCam, and SAAO. We find the planet has a radius of 1.009(-0.035)(+0.036)R(Jup) and an insolation of 9.6(-0.8)(+0.9)S(circle plus), along with a circular orbit that most likely formed via disk migration or in situ formation, rather than high-eccentricity migration mechanisms. Our analysis of the HARPS spectra yields a host star metallicity of [Fe/H] = -0.21 +/- 0.08, which does not follow the traditional trend of high host star metallicity for giant planets and does not bolster studies suggesting a difference among low- and high-mass giant planet host star metallicities. Additionally, when analyzing a sample of 216 well-characterized giant planets, we find that both high masses (4 M-Jup < M-p < 13 M-Jup) and low masses (0.5 M-Jup < M-p < 4 M-Jup), as well as both both warm (P > 10 days) and hot (P < 10 days) giant planets are preferentially located around metal-rich stars (mean [Fe/H] > 0.1). TOI-5542b is one of the oldest known warm Jupiters and it is cool enough to be unaffected by inflation due to stellar incident flux, making it a valuable contribution in the context of planetary composition and formation studies.

Abstract: Determining the architecture of multi-planetary systems is one of the cornerstones of understanding planet formation and evolution. Resonant systems are especially important as the fragility of their orbital configuration ensures that no significant scattering or collisional event has taken place since the earliest formation phase when the parent protoplanetary disc was still present. In this context, TOI-178 has been the subject of particular attention since the first TESS observations hinted at the possible presence of a near 2:3:3 resonant chain. Here we report the results of observations from CHEOPS, ESPRESSO, NGTS, and SPECULOOS with the aim of deciphering the peculiar orbital architecture of the system. We show that TOI-178 harbours at least six planets in the super-Earth to mini-Neptune regimes, with radii ranging from
1.152(-0.070)(+0.073)</textual-form>
1.152-0.070+0.073 to
2.87(-0.13)(+0.14)</textual-form> 2.87-0.13+0.14 Earth radii and periods of 1.91, 3.24, 6.56, 9.96, 15.23, and 20.71 days. All planets but the innermost one form a 2:4:6:9:12 chain of Laplace resonances, and the planetary densities show important variations from planet to planet, jumping from
1.02(-0.23)(+0.28)</textual-form> 1.02-0.23+0.28 to
0.177(-0.061)(+0.055)</textual-form> 0.177-0.061+0.055 times the Earth's density between planets c and d. Using Bayesian interior structure retrieval models, we show that the amount of gas in the planets does not vary in a monotonous way, contrary to what one would expect from simple formation and evolution models and unlike other known systems in a chain of Laplace resonances. The brightness of TOI-178 (H = 8.76 mag, J = 9.37 mag, V = 11.95 mag) allows for a precise characterisation of its orbital architecture as well as of the physical nature of the six presently known transiting planets it harbours. The peculiar orbital configuration and the diversity in average density among the planets in the system will enable the study of interior planetary structures and atmospheric evolution, providing important clues on the formation of super-Earths and mini-Neptunes.

Abstract: We report the confirmation and mass determination of three hot Jupiters discovered by the Transiting Exoplanet Survey Satellite (TESS) mission: HIP 65Ab (TOI-129, TIC-201248411) is an ultra-short-period Jupiter orbiting a bright (V = 11.1 mag) K4-dwarf every 0.98 days. It is a massive 3.213 +/- 0.078 M-J planet in a grazing transit configuration with an impact parameter of b = 1.17(-0.08)(+0.10) b=1.17-0.08+0.10 . As a result the radius is poorly constrained, 2.03(-0.49)(+0.61)R(J) 2.03-0.49+0.61 RJ . The planet's distance to its host star is less than twice the separation at which it would be destroyed by Roche lobe overflow. It is expected to spiral into HIP 65A on a timescale ranging from 80 Myr to a few gigayears, assuming a reduced tidal dissipation quality factor of Q(s)(') = 10(7) – 10(9) Qs ' =107-109 . We performed a full phase-curve analysis of the TESS data and detected both illumination- and ellipsoidal variations as well as Doppler boosting. HIP 65A is part of a binary stellar system, with HIP 65B separated by 269 AU (3.95 arcsec on sky). TOI-157b (TIC 140691463) is a typical hot Jupiter with a mass of 1.18 +/- 0.13 M-J and a radius of 1.29 +/- 0.02 R-J. It has a period of 2.08 days, which corresponds to a separation of just 0.03 AU. This makes TOI-157 an interesting system, as the host star is an evolved G9 sub-giant star (V = 12.7). TOI-169b (TIC 183120439) is a bloated Jupiter orbiting a V = 12.4 G-type star. It has a mass of 0.79 +/- 0.06 M-J and a radius of 1.09(-0.05)(+0.08)R(J) 1.09-0.05+0.08<mml:msub>RJ . Despite having the longest orbital period (P = 2.26 days) of the three planets, TOI-169b receives the most irradiation and is situated on the edge of the Neptune desert. All three host stars are metal rich with [Fe / H] ranging from 0.18 to0.24.

Abstract: Context. Long-period transiting planets provide the opportunity to better understand the formation and evolution of planetary systems. Their atmospheric properties remain largely unaltered by tidal or radiative effects of the host star, and their orbital arrangement reflects a different and less extreme migrational history compared to close-in objects. The sample of long-period exoplanets with well-determined masses and radii is still limited, but a growing number of long-period objects reveal themselves in the Transiting Exoplanet Survey Satellite (TESS) data.
Aims. Our goal is to vet and confirm single-transit planet candidates detected in the TESS space-based photometric data through spectroscopic and photometric follow-up observations with ground-based instruments.
Methods. We used high-resolution spectrographs to confirm the planetary nature of the transiting candidates and measure their masses. We also used the Next Generation Transit Survey (NGTS) to photometrically monitor the candidates in order to observe additional transits. Using a joint modeling of the light curves and radial velocities, we computed the orbital parameters of the system and were able to precisely measure the mass and radius of the transiting planets.
Results. We report the discovery of two massive, warm Jupiter-size planets, one orbiting the F8-type star TOI-5153 and the other orbiting the G1-type star NGTS-20 (=TOI-5152). From our spectroscopic analysis, both stars are metal rich with a metallicity of 0.12 and 0.15, respectively. Only TOI-5153 presents a second transit in the TESS extended mission data, but NGTS observed NGTS-20 as part of its mono-transit follow-up program and detected two additional transits. Follow-up high-resolution spectroscopic observations were carried out with CORALIE, CHIRON, FEROS, and HARPS. TOI-5153 hosts a planet with a period of 20.33 days, a planetary mass of 3.26(-0.17)(+0.18) Jupiter masses (M-j), a radius of 1.06(-0.04)(+0.04)R(J), and an orbital eccentricity of 0.091(-0.02)(6)(+0.024). NGTS-20 b is a 2.98(-)(0.)(15)(+0.16) M-J planet with a radius of 1.07(-0.0)(4)(+0.04) R-J on an eccentric (0.432(-0.023)(+0.023)) orbit with an orbital period of 54.19 days. Both planets are metal enriched and their heavy element content is in line with the previously reported mass-metallicity relation for gas giants.
Conclusions. Both warm Jupiters orbit moderately bright host stars, making these objects valuable targets for follow-up studies of the planetary atmosphere and measurement of the spin-orbit angle of the system.