Ground-based transit observations of the HAT-P-18, HAT-P-19, HAT-P-27/WASP-40 and WASP-21 systems

TL;DR

This study monitored four exoplanet systems over three years to detect transit timing variations, refining their orbital parameters and confirming previous measurements, but found no significant TTVs.

Contribution

The paper provides new transit observations and refined orbital parameters for four exoplanets, confirming previous findings and demonstrating the stability of their transit timings.

Findings

No significant TTVs detected in any system

Orbital parameters refined and confirmed

Transit timings consistent with previous studies

Abstract

As part of our ongoing effort to investigate transit timing variations (TTVs) of known exoplanets, we monitored transits of the four exoplanets HAT-P-18b, HAT-P-19b, HAT-P-27b/WASP-40b and WASP-21b. All of them are suspected to show TTVs due to the known properties of their host systems based on the respective discovery papers. During the past three years 46 transit observations were carried out, mostly using telescopes of the Young Exoplanet Transit Initiative. The analyses are used to refine the systems orbital parameters. In all cases we found no hints for significant TTVs, or changes in the system parameters inclination, fractional stellar radius and planet to star radius ratio. However, comparing our results with those available in the literature shows that we can confirm the already published values.