Transit photometry of K2-139. The top panel shows the combined K2 and CHEOPS light curve, phase folded and with all the systematics and the red-noise wavelets subtracted. The original data points are plotted as small gray points, and the larger red circles are the same data binned in phase, with a bin width corresponding to 10 minutes. Below are the residuals to our best-fitting model. The lower panel shows the individual K2 and CHEOPS light curves, labeled with the corresponding instrument name and the UT date of midtransit, and vertically offset for clarity. In all cases, our best-fitting model is shown as a solid green line.