The Transiting System GJ1214: High-Precision Defocused Transit Observations and a Search for Evidence of Transit Timing Variation

TL;DR

This study presents high-precision defocused transit observations of GJ1214b, analyzes transit timing variations using Bayesian methods, and finds no significant evidence of TTVs, refining the system's orbital parameters.

Contribution

It provides the first high-precision photometry using defocusing techniques and applies Bayesian analysis to search for TTVs in GJ1214b's transits.

Findings

Transit times measured with 10s uncertainty.

Orbital period uncertainty reduced by a factor of two.

No significant evidence of transit timing variations.

Abstract

Aims: We present 11 high-precision photometric transit observations of the transiting super-Earth planet GJ1214b. Combining these data with observations from other authors, we investigate the ephemeris for possible signs of transit timing variations (TTVs) using a Bayesian approach. Methods: The observations were obtained using telescope-defocusing techniques, and achieve a high precision with random errors in the photometry as low as 1mmag per point. To investigate the possibility of TTVs in the light curve, we calculate the overall probability of a TTV signal using Bayesian methods. Results: The observations are used to determine the photometric parameters and the physical properties of the GJ1214 system. Our results are in good agreement with published values. Individual times of mid-transit are measured with uncertainties as low as 10s, allowing us to reduce the uncertainty in the orbital period by a factor of two. Conclusions: A Bayesian analysis reveals that it is highly improbable that the observed transit times is explained by TTV, when compared with the simpler alternative of a linear ephemeris.