Carina M. Persson

Context. Gas giant planets with orbital periods of P ∼8–200 d, known as warm Jupiters, are thought to be largely unaffected by the tidal interactions that can often erase valuable information on the dynamical histories of hot Jupiters. Their orbital eccentricities ( e ) and stellar obliquities are therefore expected to be preserved, making them valuable probes of giant-planet formation and migration. Aims. Our aim is to identify and characterise transiting warm Jupiters and expand the sample of well-characterised systems and enable further studies of giant-planet formation and migration. Methods. We analysed TESS transit photometry, together with ground-based radial velocity (RV) measurements. We performed a joint fit of the photometric and spectroscopic data from the TS23 and FIES spectrographs to determine the planetary and orbital parameters. Results. We report on the discovery and characterisation of two new, transiting warm Jupiters; TOI-5120 b ( M _p = 1.23 ± 0.05 M _J , R _p = 0.969 ± 0.017 R _J , P = 24.91645 ± 0.00002 d, e = 0.10 ± 0.02) and TOI-5699 b ( M _p = 0.25 ± 0.03 M _J , R _p = 0.996 ± 0.015 R _J , P = 22.01850 ± 0.00004 d, e = 0.30 _−0.08 ^+0.09 ). We also refined the parameters of the known warm Jupiter TOI-2158 b ( M _p = 0.87 ± 0.04 M _J , R = 0.899 ± 0.015 R _J , P = 8.60079 _−0.00001 ^+0.00002 d, e = 0.028 _−0.014 ^+0.013 ). In addition, we detected an outer planetary companion, TOI-2158 c ( M _p sin i = 1.62 ± 0.13 M _J , P = 414.5 _−1.6 ^+1.5 d, e = 0.54 ± 0.04), and identified a long-term RV trend that could indicate another planetary companion on a wide orbit. Conclusions. The diverse architectures of these systems, particularly the presence and absence of outer companions, highlight the range of dynamical pathways leading to warm Jupiters.

Despite decades of research on hot Jupiters, there are still several theories for their formation. Perhaps hot Jupiters form in several ways. Atmospheric and dynamical studies have the capability to constrain the formation scenarios. However, potential targets have to be well characterized before these observations can further constrain the theories. We present the confirmation and characterization of five hot and warm Jupiters discovered by the TESS space mission. Using TESS data combined with ground-based observations, we determine the masses, radii, and other parameters of TOI-2040 b, TOI-2049 b, TOI-2578 b, TOI-4427 b, and TOI-4458 b. Three of the planets have equilibrium temperatures of about 1800 K while two have temperatures of about 1000 K. Particularly interesting for future atmospheric characterizations are TOI-2578 b and TOI-4427 b, because of their low density and large transmission spectroscopy metric. TOI-4458 b is of special interest because it is in the northern PLATO field. It appears that TOI-2040 b has a small, but measurable eccentricity.

Context. Spin-orbit obliquity measurements of hot-Jupiter systems constrain giant planet migration and tidal evolution. In binary systems, combining stellar obliquities with the orbit-orbit angle ( γ ) between the planetary and stellar companion orbits provides further insight into the dynamical influence of stellar companions. Aims. Here we aim to determine the projected obliquity ( λ ) of the hot Jupiter TOI-1333Ab ( P ≈ 4.72 d, M _p ≈ 2.4 M _J ) and place the system in the context of hot-Jupiter migration and tidal realignment in binary systems. Methods. We analysed spectroscopic observations obtained during planetary transit to model the Rossiter-McLaughlin effect and derive the projected obliquity. We combined this measurement with published system parameters and constraints on the wide stellar companion orbit to assess plausible migration scenarios. Results. We measure a projected obliquity of λ =-5 ± 10°, showing that TOI-1333Ab is well aligned with the stellar spin axis of its F-type host star. The low obliquity and its modest eccentricity ( e = 0.073 _−0.052 ^+0.092 ) are consistent with either disc-driven migration or high-eccentricity migration followed by efficient tidal circularisation and realignment. With an effective temperature of 6274 ± 97 K, the host star lies above the canonical Kraft break where the systems are frequently misaligned. Despite this, we find the system to be well aligned. In comparison with other planetary systems in binaries, TOI-1333 occupies a relatively isolated region in projected obliquity-orbit-orbit angle ( γ = 81.5 ± 1.1°) space, making it a valuable system for studying the interplay between migration, tides, and stellar companions.

The discovered planets in apparent single-planet systems (hereafter singles) and those in systems with multiple detected planets (hence-forth multis) exhibit a rich diversity of physical and orbital properties. However, it is still debated whether the observed singles and multis originate from the same underlying planet population. We investigate the differences and similarities between 1730 singles and 1522 multis in a catalogue of confirmed transiting planets orbiting main-sequence stars with spectral classes ranging from late-M to late-F. After we removed the hot Jupiters, the planet types and their fractional numbers were similar for the multis and singles hosted by FGK-type stars. Furthermore, the median radii of both the singles and the multis increase with host star temperature already from late- to early-type M dwarfs and further up to F stars. Our analyses show that the singles are larger on average than the multis in our F, G, K, and M samples. However, after we excluded the hot Jupiters, the radius distributions of the singles and multis orbiting FGK stars are statistically indistinguishable, particularly at R < 4 R _⊕ . In the FGK sample, we also identified an unexpected and significant overabundance of multis, compared to singles, at radii of ≈1.4–1.6 R _⊕ . For the early- and late-type M samples, our work indicates that the multis are smaller on average than the singles and that the radius distributions of the multis and singles are different, except for the planets with R < 4 R _⊕ hosted by early-type M dwarfs. Nevertheless, these results for the two M samples are inconclusive because the sample sizes of 167 and 101 planets are limited. In conclusion, our analyses reveal that the singles and multis, excluding the hot Jupiters, orbiting FGK stars are overall consistent with originating from the same underlying population based on their planet types and radii. This interpretation is, however, not applicable within the region of the overabundance of multis at ≈1.4–1.6 R _⊕ identified in this work, which is an intriguing feature warranting further investigations.

Context . The structure and evolution of close-in exoplanets are shaped by atmospheric loss and migration processes, which give rise to key population features such as the hot Neptune desert, ridge, and savanna – regions of the period-radius space whose boundaries offer critical insights into planetary formation and survival. Aims . As part of the KESPRINT collaboration, we selected the TESS transiting planet candidate TOI-3862.01 for radial velocity follow-up to confirm its planetary nature and characterize its mass and bulk properties. This planet candidate is of particular interest due to its position in the middle of the hot Neptune desert, making it a valuable probe for testing theories of planet migration and atmospheric loss. Methods . We confirmed the planetary nature and determined the mass of TOI-3862.01 (hereinafter TOI-3862 b) by performing a joint fit with both transit and radial velocity data, precisely characterizing the bulk properties of this planet. Results . TOI-3862b is a super-Neptune on a 1.56-day orbit around a Sun-like star with an effective temperature of 5300±50 K. It has a mass of 53.7 _−2.9 ^+2.8 M _⊕ and a radius of 5.53 ± 0.18 R _⊕ , corresponding to a density of 1.7±0.2 g/cm ³ . This places it among the rare population of hot and dense super-Neptune desert planets. Conclusions . TOI-3862b, residing deep in the hot Neptune desert, represents a rare occurrence in an otherwise sparsely populated region, offering a valuable opportunity to probe the processes that may allow planets to survive in such environments.

TOI-282 is a bright (V = 9.38) F8 main-sequence star known to host three transiting long-period ( P _b = 22.9 d, P _c = 56.0 d, and P _d = 84.3 d) small ( R _p ≈ 2–4 R _⊕ ) planets. The orbital period ratio of the two outermost planets, namely TOI-282 c and d, is close to the 3:2 commensurability, suggesting that the planets might be trapped in a mean motion resonance. We combined space-borne photometry from the TESS telescope with high-precision HARPS and ESPRESSO Doppler measurements to refine orbital parameters, measure the planetary masses, and investigate the architecture and evolution of the system. We performed a Markov chain Monte Carlo joint analysis of the transit light curves and radial velocity time series, and carried out a dynamical analysis to model transit timing variations and Doppler measurements along with N -body integration. In agreement with previous results, we found that TOI-282 b, c, and d have radii of R _b = 2.69 ± 0.23 R _⊕ , R _c = 4.13 _−0.14 ^+0.16 R _⊕ , and R _d = 3.11 ± 0.15 R _⊕ , respectively. We measured planetary masses of M _b = 6.2 ± 1.6 M _⊕ , M _c = 9.2 ± 2.0 M _⊕ , and M _d = 5.8 _−1.1 ^+0.9 M _⊕ , which imply mean densities of ρ _b = 1.8 _−0.6 ^+0.7 g cm ⁻³ , ρ _c = 0.7 ± 0.2 g cm ⁻³ , and ρ _d = 1.1 _{−0.2 +0.3} g cm ⁻³ , respectively. The three planets may be water worlds, making TOI-282 an interesting system for future atmospheric follow-up observations with JWST and ELT.

We present the detection and characterisation of the TOI-1438 multi-planet system discovered by TESS. We collected a series of follow-up observations including high-spectral resolution observations with HARPS-N over a period of five years. Our modelling shows that the K0V star hosts two transiting sub-Neptunes with Rb = 3.04 +/- 0.19 RE, Rc = 2.75 +/- 0.14 RE, Mb = 9.4 +/- 1.8 ME, and Mc = 10.6 +/- 2.1 ME. The orbital periods of planets b and c are 5.1 and 9.4 days, respectively, corresponding to instellations of 145 +/- 10 and 65 +/- 4 FE. The bulk densities are 1.8 +/- 0.5 and 2.9 +/- 0.7 g cm-3, respectively, suggesting a volatile-rich interior composition. We computed a set of planet interior structure models. Planet b presents a high-metallicity envelope that can accommodate up to 2.5 % in H/He in mass, while planet c cannot have more than 0.2 % as H/He in mass. For any composition of the core considered (Fe-rock or ice-rock), both planets would require a volatile-rich envelope. In addition to the two planets, the radial velocity (RV) data clearly reveal a third signal, likely coming from a non-transiting planet, with an orbital period of 7.6 +1.6 -2.4 years and a radial velocity semi-amplitude of 35+3-5 m s-1. Our best fit model finds a minimum mass of 2.1 +/- 0.3 MJ and an eccentricity of 0.25+0.08-0.11. However, several RV activity indicators also show strong signals at similar periods, suggesting this signal might (partly) originate from stellar activity. More data over a longer period of time are needed to conclusively determine the nature of this signal. If it is confirmed as a triple-planet system, TOI-1438 would be one of the few detected systems to date characterised by an architecture with two small, short-period planets and one massive, long-period planet, where the inner and outer systems are separated by an orbital period ratio of the order of a few hundred.

Using high-precision photometry, NASA’s TESS space mission has discovered many intriguing transiting planet candidates. These discoveries require ground-based follow-up observations, including high-precision Doppler spectroscopy, to rule out false positive scenarios and measure the mass of the transiting planets. In this study, we present an intensive Doppler follow-up campaign of the TESS object of interest TOI-2427, carried out with the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph to determine the mass of the previously validated transiting planet (TOI-2427 b) and search for additional orbiting companions. By analyzing TESS transit photometry alongside our HARPS radial velocity measurements, we spectroscopically confirmed the transiting planet TOI-2427 b, which orbits its host star every ∼ 1.3 d. We also discovered the presence of a second non-transiting planetary companion with an orbital period of ∼ 5.15 d, which is very close to four times the orbital period of the inner transiting planet. We found that TOI-2427 b is a short-period, high-density super-Earth with a mass of M_b = 5.69_−0.50^+0.51 M_⊕ and a radius of R_b = 1.64_−0.11^+0.12 R_⊕, implying a mean density of ρ_b = 7.1_−0.4^+0.8 g cm⁻³. Its interior seems to be composed of a predominantly iron core and a silicate mantle and crust. Despite its high density, it is unlikely that TOI-2427 b can sustain any atmosphere composed of lighter gases; however, it could still retain heavier gases. The outer non-transiting planet TOI-2427 c has a minimum mass of M_c sin i_c = 6.46_−0.78^+0.79 M_⊕. Assuming that TOI-2427 b and c are coplanar, a statistical analysis suggests that planets with a mass of ∼ 6.5 M_⊕ tend to have radii around 2.7_−0.8^+1.1 R_⊕. This would place TOI-2457 c near the sub-Neptune regime, while also leaving open the possibility of it being a super-Earth.