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1. TOI-3568 b: A super-Neptune in the sub-Jovian desert

   https://doi.org/10.1051/0004-6361/202450334  

   Martioli, E; Petrucci, R P; Jofré, E; Hébrard, G; Ghezzi, L; Gómez_Maqueo_Chew, Y; Díaz, R F; Perottoni, H D; Garcia, L H; Rapetti, D; et al (October 2024, Astronomy & Astrophysics)

   The sub-Jovian desert is a region in the mass-period and radius-period parameter space that typically encompasses short-period ranges between super-Earths and hot Jupiters, and exhibits an intrinsic dearth of planets. This scarcity is likely shaped by photoevaporation caused by the stellar irradiation received by giant planets that have migrated inward. We report the detection and characterization of TOI-3568 b, a transiting super-Neptune with a mass of 26.4 ± 1.0 M_⊕, a radius of 5.30 ± 0.27 R_⊕, a bulk density of 0.98 ± 0.15 g cm⁻³, and an orbital period of 4.417965 (5) d situated in the vicinity of the sub-Jovian desert. This planet orbiting a K dwarf star with solar metallicity was identified photometrically by the Transiting Exoplanet Survey Satellite (TESS). It was characterized as a planet by our high-precision radial-velocity (RV) monitoring program using MAROON-X at Gemini North, supplemented with additional observations from the SPICE large program with SPIRou at CFHT. We performed a Bayesian MCMC joint analysis of the TESS and ground-based photometry, and MAROON-X and SPIRou RVs, to measure the orbit, radius, and mass of the planet, as well as a detailed analysis of the high-resolution flux and polarimetric spectra to determine the physical parameters and elemental abundances of the host star. Our results reveal TOI-3568 b to be a hot super-Neptune rich in hydrogen and helium, with a core of heavier elements of between 10 and 25 M_⊕in mass. We analyzed the photoevaporation status of TOI-3568 b and find that it experiences one of the highest extreme-ultraviolet (EUV) luminosities among planets with a mass of M_p< 2 M_Nep, yet it has an evaporation lifetime exceeding 5 Gyr. Positioned in the transition between two significant populations of exoplanets on the mass-period and energy diagrams, this planet presents an opportunity to test theories concerning the origin of the sub-Jovian desert. 

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2. Searching for GEMS: Confirmation of TOI-5573 b, a Cool, Saturn-like Planet Orbiting an M Dwarf ^*

   https://doi.org/10.3847/1538-3881/addc51  

   Fernandes, Rachel B; Kanodia, Shubham; Delamer, Megan; Hotnisky, Andrew; Han, Te; Cañas, Caleb I; Libby-Roberts, Jessica; Reji, Varghese; Gupta, Arvind F; Alvarado-Montes, Jaime A; et al (June 2025, The Astronomical Journal)

   Abstract We present the confirmation of TOI-5573 b, a Saturn-sized exoplanet on an 8.79 days orbit around an early M dwarf (3790 K, 0.59R_⊙, 0.61M_⊙, 12.30 Jmag). TOI-5573 b has a mass of $112_{-19}^{+18}$M_⊕(0.35 ± 0.06M_Jup) and a radius of 9.75 ± 0.47R_⊕(0.87 ± 0.04R_Jup), resulting in a density of $0.66_{-0.13}^{+0.16}$g cm⁻³, akin to that of Saturn. The planet was initially discovered by the Transiting Exoplanet Survey Satellite (TESS) and confirmed using a combination of 11 transits from four TESS Sectors (20, 21, 47, and 74), ground-based photometry from the Red Buttes Observatory, and high-precision radial velocity data from the Habitable-zone Planet Finder and NN-EXPLORE Exoplanet Investigations with Doppler spectrographs, achieving a 5σprecision on the planet’s mass. TOI-5573 b is one of the coolest Saturn-like exoplanets discovered around an M-dwarf, with an equilibrium temperature of only 528 ± 10 K, making it a valuable target for atmospheric characterization. Saturn-like exoplanets around M dwarfs likely form through core accretion, with increased disk opacity slowing gas accretion and limiting their mass. The host star’s supersolar metallicity supports core accretion, but uncertainties in M-dwarf metallicity estimates complicate definitive conclusions. Compared to other GEMS (Giant Exoplanets around M-dwarf Stars) orbiting metal-rich stars, TOI-5573 b aligns with the observed pattern that giant planets preferentially form around M-dwarfs with supersolar metallicity. Further high-resolution spectroscopic observations are needed to explore the role of stellar metallicity in shaping the formation and properties of giant exoplanets like TOI-5573 b. 

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3. TOI-1685 b Is a Hot Rocky Super-Earth: Updates to the Stellar and Planet Parameters of a Popular JWST Cycle 2 Target

   https://doi.org/10.3847/2041-8213/ad5b52  

   Burt, Jennifer A; Hooton, Matthew J; Mamajek, Eric E; Barragán, Oscar; Millholland, Sarah C; Fairnington, Tyler R; Fisher, Chloe; Halverson, Samuel P; Huang, Chelsea X; Brady, Madison; et al (August 2024, The Astrophysical Journal Letters)

   Abstract We present an updated characterization of the TOI-1685 planetary system, which consists of aP_b= 0.69 day ultra-short-period super-Earth planet orbiting a nearby (d= 37.6 pc) M2.5V star (TIC 28900646, 2MASS J04342248+4302148). This planet was previously featured in two contemporaneous discovery papers, but the best-fit planet mass, radius, and bulk density values were discrepant, allowing it to be interpreted either as a hot, bare rock or a 50% H₂O/50% MgSiO₃water world. TOI-1685 b will be observed in three independent JWST Cycle 2 programs, two of which assume the planet is a water world, while the third assumes that it is a hot rocky planet. Here we include a refined stellar classification with a focus on addressing the host star’s metallicity, an updated planet radius measurement that includes two sectors of TESS data and multicolor photometry from a variety of ground-based facilities, and a more accurate dynamical mass measurement from a combined CARMENES, InfraRed Doppler, and MAROON-X radial velocity data set. We find that the star is very metal-rich ([Fe/H] ≃ +0.3) and that the planet is systematically smaller, lower mass, and higher density than initially reported, with new best-fit parameters ofR_pl= 1.468 ${}_{-0.051}^{+0.050}$R_⊕andM_pl= ${3.03}_{-0.32}^{+0.33}$M_⊕. These results fall in between the previously derived values and suggest that TOI-1685 b is a hot rocky planet with an Earth-like density (ρ_pl= 5.3 ± 0.8 g cm⁻³, or 0.96ρ_⊕), high equilibrium temperature (T_eq= 1062 ± 27 K), and negligible volatiles, rather than a water world. 

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4. Identification of the Top TESS Objects of Interest for Atmospheric Characterization of Transiting Exoplanets with JWST

   https://doi.org/10.3847/1538-3881/ad3068  

   Hord, Benjamin J; Kempton, Eliza M-R; Evans-Soma, Thomas M; Latham, David W; Ciardi, David R; Dragomir, Diana; Colón, Knicole D; Ross, Gabrielle; Vanderburg, Andrew; de_Beurs, Zoe L; et al (April 2024, The Astronomical Journal)

   Abstract JWST has ushered in an era of unprecedented ability to characterize exoplanetary atmospheres. While there are over 5000 confirmed planets, more than 4000 Transiting Exoplanet Survey Satellite (TESS) planet candidates are still unconfirmed and many of the best planets for atmospheric characterization may remain to be identified. We present a sample of TESS planets and planet candidates that we identify as “best-in-class” for transmission and emission spectroscopy with JWST. These targets are sorted into bins across equilibrium temperatureT_eqand planetary radiusR_pand are ranked by a transmission and an emission spectroscopy metric (TSM and ESM, respectively) within each bin. We perform cuts for expected signal size and stellar brightness to remove suboptimal targets for JWST. Of the 194 targets in the resulting sample, 103 are unconfirmed TESS planet candidates, also known as TESS Objects of Interest (TOIs). We perform vetting and statistical validation analyses on these 103 targets to determine which are likely planets and which are likely false positives, incorporating ground-based follow-up from the TESS Follow-up Observation Program to aid the vetting and validation process. We statistically validate 18 TOIs, marginally validate 31 TOIs to varying levels of confidence, deem 29 TOIs likely false positives, and leave the dispositions for four TOIs as inconclusive. Twenty-one of the 103 TOIs were confirmed independently over the course of our analysis. We intend for this work to serve as a community resource and motivate formal confirmation and mass measurements of each validated planet. We encourage more detailed analysis of individual targets by the community. 

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5. Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley

   https://doi.org/10.1051/0004-6361/202348180  

   Bonfanti, A; Brady, M; Wilson, T G; Venturini, J; Egger, J A; Brandeker, A; Sousa, S G; Lendl, M; Simon, A E; Queloz, D; et al (February 2024, Astronomy & Astrophysics)

   Context. TOI-732 is an M dwarf hosting two transiting planets that are located on the two opposite sides of the radius valley. Inferring a reliable demographics for this type of systems is key to understanding their formation and evolution mechanisms. Aims. By doubling the number of available space-based observations and increasing the number of radial velocity (RV) measurements, we aim at refining the parameters of TOI-732 b and c. We also use the results to study the slope of the radius valley and the density valley for a well-characterised sample of M-dwarf exoplanets. Methods. We performed a global Markov chain Monte Carlo analysis by jointly modelling ground-based light curves and CHEOPS and TESS observations, along with RV time series both taken from the literature and obtained with the MAROON-X spectrograph. The slopes of the M-dwarf valleys were quantified via a support vector machine (SVM) procedure. Results. TOI-732b is an ultrashort-period planet (P= 0.76837931_-0.00000042^+0.0000039days) with a radiusR_b= 1.325_-0.058^+0.057R_⊕, a massM_b= 2.46 ± 0.19M_⊕, and thus a mean densityρ_b= 5.8_-0.8^+1.0g cm^-3, while the outer planet atP= 12.252284 ± 0.000013 days hasR_c= 2.39_-0.11^+0.10R_⊕,M_c= 8.04_-0.48^+0.50M_⊕, and thusρ_c= 3.24_-0.43^+0.55g cm^-3. Even with respect to the most recently reported values, this work yields uncertainties on the transit depths and on the RV semi-amplitudes that are smaller up to a factor of ~1.6 and ~2.4 for TOI-732 b and c, respectively. Our calculations for the interior structure and the location of the planets in the mass-radius diagram lead us to classify TOI-732 b as a super-Earth and TOI-732 c as a mini-Neptune. Following the SVM approach, we quantified d logR_p,valley/ d logP= -0.065_-0.013^+0.024, which is flatter than for Sun-like stars. In line with former analyses, we note that the radius valley for M-dwarf planets is more densely populated, and we further quantify the slope of the density valley as d log ρ^_valley/ d logP= -0.02_-0.04^+0.12. Conclusions. Compared to FGK stars, the weaker dependence of the position of the radius valley on the orbital period might indicate that the formation shapes the radius valley around M dwarfs more strongly than the evolution mechanisms. 

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