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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. 

TOI-2015 is a known exoplanetary system around an M4 dwarf star, consisting of a transiting sub-Neptune planet in a 3.35-day orbital period, TOI-2015 b, accompanied by a non-transiting companion, TOI-2015 c. High-precision radial-velocity measurements were taken with the MAROON-X spectrograph, and high-precision photometric data were collected, primarily using the SPECULOOS, MUSCAT, TRAPPIST and LCOGT networks. We collected 63 transit light curves and 49 different transit epochs for TOI-2015 b. We recharacterized the target star by combining optical spectra obtained by the MAROON-X, Shane/KAST and IRTF/SpeX spectrographs, Bayesian model averaging (BMA) and spectral energy distribution (SED) analysis. The TOI-2015 host star is aK= 10.3 mag M4-type dwarf with a subsolar metallicity of [Fe/H] = −0.31 ± 0.16, and an effective temperature ofT_eff≈ 3200 K. Our photodynamical analysis of the system strongly favors the 5:3 mean-motion resonance and in this scenario the planet b (TOI-2015 b) has an orbital period ofP_b= 3.34 days, a mass ofM_p= 9.02_-0.36^+0.32M_⊕, and a radius ofR_p= 3.309_-0.011^+0.013R_⊕, resulting in a density ofρ_p= 0.25 ± 0.01ρ_⊕= 1.40 ± 0.06 g cm⁻³; this is indicative of a Neptune-like composition. Its transits exhibit large (> 1 hr) timing variations characteristic of an outer perturber in the system. We performed a global analysis of the high-resolution radial-velocity measurements, the photometric data, and the TTVs, and inferred that TOI-2015 hosts a second planet, TOI-2015 c, in a non-transiting configuration. Our analysis places it near a 5:3 resonance with an orbital period ofP_c= 5.583 days and a mass ofM_p= 8.91_-0.40^+0.38M_⊕. The dynamical configuration of TOI-2015 b and TOI-2015 c can be used to constrain the system’s planetary formation and migration history. Based on the mass-radius composition models, TOI-2015 b is a water-rich or rocky planet with a hydrogen-helium envelope. Moreover, TOI-2015 b has a high transmission-spectroscopic metric (TSM=149), making it a favorable target for future transmission spectroscopic observations with theJWSTto constrain the atmospheric composition of the planet. Such observations would also help to break the degeneracies in theoretical models of the planet’s interior structure.