Comparative study of nearly-grazing and fully-grazing exoplanet system parameters derived with TESS and ground-based instruments

Grazing transiting systems are rare and difficult to parameterize due to their partial transit geometry. We investigated a sample of 43 nearly-grazing to fully-grazing transiting exoplanetary systems, using datasets provided by the Transiting Exoplanet Satellite Survey (TESS), aiming first to refine major system parameters. We focus on the two parameters, impact parameter b and planetary radius R-p, through a comparison of TESS light curves with ground-based light curves. We investigate if there is a potential systematic trend between ground-based and space-based investigations that would possibly lead to a redefinition of the grazing nature of those exoplanetary systems. Our results have shown that the b value is confirmed for most of the systems within 2 sigma, and refined significantly for Kilodegree Extremely Little Telescope (KELT)-8 b, while the uncertainty on b was improved for five systems with b > 0.8. The R-p measurements of four systems were successfully refined, while the uncertainty of R-p was improved for the majority of exoplanets with b > 0.9. Furthermore, a systematic trend is more pronounced for systems with b > 0.9, where there is a mean over-estimation on the ground-based derived R-p by 0.15R(J). We concluded eventually that from our sample only five systems are truly grazing, while four systems that were considered as grazing are not.