Analyzing FFIs to Identify False Positives within TESS Candidates

After follow-up, many TESS Objects of Interest are found to be nearby eclipsing binaries. In this scenario, a pair of binary stars visually close to the target star produces photometric signals that are mistaken for those produced by a transiting planet. Identifying such false positives through follow-up observations allows future observing resources to be focused on the remaining active TOIs. Yet, on the other hand, data that reveals a false positive will likely never be published. As such, it is beneficial to rule out false positives, if possible, before follow-up observing resources have been spent on them. Despite TESS’s large pixel scale of 21”, it is possible to identify NEBs for which the target star and the binary are separated by more than ~20” using the TESS full-frame images. In this project, we used AstroImageJ to reduce FFIs and searched for NEBs in a sample of 34 TOIs. This sample contains targets whose QLP reports show hints of NEBs, which include centroid offsets and depth-aperture correlation, as well as secondary transits for candidates with nominally small planet radii. Among these candidates, 10 were found to be NEBs and are now retired. It is estimated that these results have saved ~30 hours of telescope time.