A Systematic Study of the TESS Photometry of the Magnetic O-type Stars

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Barron, James
astronomy , stellar magnetism , massive stars , TESS photometry , O-type stars
Large spectropolarimetric surveys have revealed that a relatively rare sub-population (<10%) of massive O-type stars possess detectable photospheric magnetic fields. There are many open questions surrounding the magnetic fields of O-type stars, including their origin, impact on stellar evolutionary paths and role in observed O star spectral and photometric variability. However, the small number of known magnetic O stars has significantly hindered our understanding of their global properties. Only eleven Galactic magnetic O stars have been confirmed, and another six magnetic candidates have been identified in the Magellanic Clouds. Recent high-precision photometry obtained by the Transiting Exoplanet Survey Satellite (TESS) is providing significant advancements to the fields of massive star magnetism and asteroseismology. Diverse variability has been seen in the TESS light curves of O-type stars, offering an unprecedented opportunity to study their physical properties. We have performed a systematic analysis of the TESS light curves of the known magnetic O stars and extra-galactic magnetic candidates to characterize their variability and search for signatures of rotational modulation due to co-rotating magnetospheres. We perform custom light curve extractions in order to investigate systematics related to the detrending process and search for contaminating signals from blended sources. We detect a variety of signals in the TESS light curves of the Galactic magnetic O stars, including rotational modulation, stochastic low-frequencies and possible coherent low-frequency pulsations. We detect rotational modulation in two of the extra-Galactic magnetic candidates. These results have important implications for understanding the origins of O star photometric variability and will help inform future searches for new magnetic O star candidates using TESS photometry.
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