On the parameter refinement of inflated exoplanets with large radius uncertainty based on TESS observations

Abstract

We revisited 10 known exoplanetary systems using publicly available data provided by the transiting exoplanet survey satellite (TESS). The sample presented in this work consists of short period transiting exoplanets, with inflated radii and large reported uncertainty on their planetary radii. The precise determination of these values is crucial in order to develop accurate evolutionary models and understand the inflation mechanisms of these systems. Aiming to evaluate the planetary radius measurement, we made use of the planet-to-star radii ratio, a quantity that can be measured during a transit event. We fit the obtained transit light curves of each target with a detrending model and a transit model. Furthermore, we used emcee, which is based on a Markov chain Monte Carlo approach, to assess the best fit posterior distributions of each system parameter of interest. We refined the planetary radius of WASP-140 b by approximately 12%, and we derived a better precision on its reported asymmetric radius uncertainty by approximately 86 and 67%. We also refined the orbital parameters of WASP-120 b by 2𝜎. Moreover, using the high-cadence TESS datasets, we were able to solve a discrepancy in the literature, regarding the planetary radius of the exoplanet WASP-93 b. For all the other exoplanets in our sample, even though there is a tentative trend that planetary radii of (near-) grazing systems have been slightly overestimated in the literature, the planetary radius estimation and the orbital parameters were confirmed with independent observations from space, showing that TESS and ground-based observations are overall in good agreement.

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

“…The measurements derived based on TESS results from the literature and our own work are represented by circles in corresponding colors exceeds unity for these two exoplanets. The exoplanets WASP-174 b, WASP-168 b, and WASP-177 b of Group D, are confirmed as grazing systems, while, on the other hand, WASP-140 b, and WASP-93 b(Alexoudi, 2022), and WASP-183 b and WASP-34 b (this work), are no longer considered, according to this criterion, as grazing systems.…”

“…The parameter refinement/confirmation for $$$ {R}_{\mathrm{p}} $$$, $$$ {R}_{\mathrm{p}}/{R}_{\mathrm{s}} $$$ and $$$ b $$$ measured for a rich sample of nearly‐grazing to fully‐grazing transiting exoplanetary systems is presented in the following Table 1. These references contain studies of ground‐based and TESS observations, along with our, recently published work on the subject (Alexoudi, 2022).…”

“…However, there are two exceptions, that is, the exoplanets WASP‐120 b and KELT‐8 b. The $$$ b $$$ measurement of WASP‐120 b, reported in Alexoudi (2022), has a difference of $$$ 2.6\sigma $$$ with the previous ground‐based investigation, while in our current work, KELT‐8 b is found to differ by approximately $$$ 4\sigma $$$ from the ground‐based investigation of Fulton et al (2015). For KELT‐8 b, we observed a large crowding metric provided by the header at TESS's target pixel file (TPF) of this specific observation, which shows that approximately 33% of the received light was contaminated by other sources in the field‐of‐view (FOV) and it had to be corrected.…”

“…We proceeded with the data analysis as presented previously in Alexoudi (2022). Here is a brief description of the process.…”

“…Moreover, we investigate the hypothesis that ground-based observations are biased due to the grazing nature of those systems and always yield overestimated planetary radii. A trend of this scenario was observed in a small group of inflated giants with large b (b > 0.6) in Alexoudi (2022), while in the current work, we investigate a collection of well-known nearly-grazing to fully-grazing systems within a range of 0.6 < b < 1.0, observed with ground-based instruments and TESS. Our work, in combination with recently published studies involving TESS data, compares directly to these ground-based investigations and provides a confirmation or a refinement of their two aforementioned parameters and a redefinition of the grazing nature of those systems.…”