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

Abstract

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$$ b $$ and planetary radius Rp$$ {R}_{\mathrm{p}} $$, 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$$ b $$ value is confirmed for most of the systems within 2σ$$ 2\sigma $$, and refined significantly for Kilodegree Extremely Little Telescope (KELT)‐8 b, while the uncertainty on b$$ b $$ was improved for five systems with b>0.8$$ b>0.8 $$. The Rp$$ {R}_{\mathrm{p}} $$ measurements of four systems were successfully refined, while the uncertainty of Rp$$ {R}_{\mathrm{p}} $$ was improved for the majority of exoplanets with b>0.9$$ b>0.9 $$. Furthermore, a systematic trend is more pronounced for systems with b>0.9$$ b>0.9 $$, where there is a mean overestimation on the ground‐based derived Rp$$ {R}_{\mathrm{p}} $$ by 0.15RJ$$ 0.15{R}_{\mathrm{J}} $$. We concluded eventually that from our sample only five systems are truly grazing, while four systems that were considered as grazing are not.