With the TESS satellite observing most of the WASP planets as it surveys the sky, one can use the space-based data quality to look for “transit timing variations” in the WASP planet transits. Such TTVs — slight changes in the time of recurrence of a transit — can be caused by the gravitational perturbation of other planets in the system, and thus can reveal the presence of extra planets even when they themselves do not transit.
A new paper by Kyle Pearson, of the University of Arizona, reports evidence for TTVs in the TESS light-curves of WASP-18 and WASP-126.
Here is the TESS light-curve of WASP-18, showing the transits of the known planet WASP-18b:
And here are possible changes in the transit times, varying systematically with a 2.1-day period (red line):
Here now is the TESS light-curve of WASP-126, showing transits of WASP-126b:
And here are possible TTVs varying systematically with a period of 7.7 days (red line):
The evidence is not yet sufficiently water-tight to be sure of the existence of the extra planets, without adding in further data, but this study points to lots of similar work using TESS data as it continues its multi-year survey.