Folded transit photometry

Transit photometry is perhaps the most successful method for detecting exoplanets to date. However, a substantial amount of signal processing is needed since the dip in the signal detected, an indication that there is a planet in transit, is minuscule compared to the overall background signal due mainly to its host star. In this paper, we put forth a doable and straightforward method to enhance the signal and reduce noise. We discuss how to achieve higher planetary signals by subtracting equal halves of the host star - a folded detection. This results in a light curve with a double peak-to-peak signal, 2R_p^2/R_s^2, compared to the usual transit. We derive an expression of the light curve and investigate the effect of two common noises: the white Gaussian background noise and the noise due to the occurrences of sunspots. We show that in both simulation and analytical expression, the folded transit reduces the effective noise by a factor of 1/sqrt(2). This reduction and the doubling of the signal enables (1) less number of transit measurements to get a definitive transiting planet signal and (2) detection of smaller planetary radii with the usual transit with the same number of transit data. Furthermore, we show that in the presence of multiple sunspots, the estimation of planetary parameters is more accurate. While our calculations may be very simple, it covers the basic concept of planetary transits.