The GAPS programme at TNG: LXXIV. A reanalysis of the planetary systems TOI-1272 and TOI-1694 with HARPS-N and retraction of the planetary interpretation of TOI-1272 c

Context. Hot Neptunes are close-in exoplanets that occupy a sparsely populated region of parameter space known as the hot Neptune desert. Their presence in this extreme environment is puzzling as it implies a complex history involving intense stellar radiation, atmospheric loss, and unique migration patterns that differ from more conventional Neptunes at larger orbital periods. Aims. We are running an observational programme aimed at enlarging the number of close-in Neptune-sized planets, with well-measured physical and orbital parameters. It contributes to the compilation of a statistically significant sample that will aid in clarifying the formation and migration pathways characterising this class of exoplanets. Methods. We used currently available TESS photometry, along with new (HARPS-N) and archival (HIRES) high-precision radialvelocity measurements, to review the main properties of the planetary systems TOI-1272 and TOI-1694 by means of joint-fit analyses. In the case of TOI-1272, this included Gaussian-process regressions for carefully modelling stellar activity. Results. Our final estimates of the parameters of the two systems are consistent with previous measurements but have smaller uncertainties. We identified the radial-velocity variation of TOI-1272 found in the HIRES data as stellar activity, rather than planetary in nature and, therefore, we rejected the non-transiting planet TOI-1272 c. This opens up the possibility that TOI-1272 b's eccentricity is the result of high-eccentricity migration. The larger store of data at our disposal also allowed us to point out that both TOI-1694 b and TOI-1694 c move on slightly eccentric orbits. The current orbital architecture of TOI-1694 suggests a history of migration driven by both disc and dynamical interactions.