TESS photometry of the Of?p stars HD 148937 and LMC 164-2

Recent spectropolarimetric surveys have identified a subpopulation of O stars (<10%) that possess strong (0.1-20 kG), typically dipolar magnetic fields. These fields channel the stellar wind, which results in a dense magnetosphere that co-rotates with the star. As a result, magnetic O stars show spectral and photometric variability that is modulated by rotation. With new observations provided by the Transiting Exoplanet Survey Satellite (TESS), we can now study magnetic O-star variability at the sub-mmag level. In addition, the large sky coverage provided by TESS offers the potential to identify new candidate magnetic O stars for follow-up spectropolarimetric observations. Careful analysis of known magnetic O star TESS photometry is essential to understanding how to identify rotational modulation in the larger TESS O star sample. Here we discuss the TESS photometry of HD 148937, one of the few magnetic O stars with a reported rotational period (Prot=7.03 d) short enough to be detected in a single sector (~27 d). Additionally, we show analysis of the TESS photometry of the short period magnetic candidate Of?p stars in the Magellanic Clouds, which have been observed over many sectors. We discuss issues related to detrending and contamination in the TESS pipeline processed light curves and the subsequent impact on our efforts to identify new candidate magnetic O stars.