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.
Highlights
The transiting exoplanet GJ 1214 b was discovered in 2009 by the MEarth project1 (Charbonneau et al 2008)
Combining these data with observations from other authors, we investigate the ephemeris for possible signs of transit timing variations (TTVs) using a Bayesian approach
Additional planets can be revealed via their gravitational effects on the transiting planet. This would result in telltale systematic deviations in the mid-transit times from a linear ephemeris, a phenomenon known as transit timing variation (TTV) (Agol et al 2005; Holman & Murray 2005)
Summary
The transiting exoplanet GJ 1214 b was discovered in 2009 by the MEarth project (Charbonneau et al 2008). This planet transits a nearby M dwarf (Charbonneau et al 2009), with a mass 0.15 M and the planet is generally classified as a superEarth with a mass and radius (Mp = 6.37 M⊕ and Rp = 2.74 R⊕ according to Kundurthy et al (2011), in this study we find Mp = 6.26 M⊕ and Rp = 2.85 R⊕) between that of Earth and Neptune, a type of planet that has no solar system analogue. Additional planets can be revealed via their gravitational effects on the transiting planet This would result in telltale systematic deviations in the mid-transit times from a linear ephemeris, a phenomenon known as transit timing variation (TTV) (Agol et al 2005; Holman & Murray 2005).
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