Multi-Colour Photometric Observations of Transiting Exoplanets to Verify Binary Star Systems

Abstract

Within this paper, we report the observation of transiting exoplanets, K2-29b, TrES-3b, WASP-36b, and HAT-P54b, with a focused comparison of the well defined binary system K2-29b to the proposed binary WASP-36b. Performing multicolour photometry, debayering images to three distinct colour channels, a comparison of the detrended light curves of each target is used to define parameters to identify the presence of any discrepancy between the observation, defined system models or past observations. The exoplanet system K2-29b, observed in separate red and blue filters, produced minimal deviation from expected RP /R∗ values with RP /R∗ = 0.1404 +0.0040/-0.0042 and  RP /R∗ = 0.1468 +0.0082/-0.0088 respectively. In contrast to this, we observe a significant deviation in the blue debayered value of RP /R∗ for WASP-36b, with the expected radius ratio defined to be ±RP /R∗ = 0.1368±0.0006. Initial airmass detrending model fitting for the blue debayered channel produced a value of RP /R∗ = 0.1162+0.0098/ -0.0102, with RP /R∗ Drift = 3.01σ, this later being reduced through a quadratic detrending scheme to RP /R∗ Drift = 2.11σ. Despite this model being an improved representation, this measure of RP /R∗ drift is significantly beyond the tolerance of ±1σ and as such motivates further study as this effect has been denoted in concordant research to suggest presence of a secondary star in this system.