Photometry for highly saturated TESS stars

Abstract

Saturation in TESS complicates simple aperture photometry, as flux can be lost to bleeding outside the target pixels. Halo photometry can nevertheless reconstruct good light curves of these stars, as a weighted linear combination of pixel time series from the unsaturatedwings of the PSF.Wehaveappliedthistoextract light curves for 98 bright TESS stars: we detect variability in 77, including 15 red giants, 5 δ Scuti variables, 8 stochastic low-frequency variables, and 8 eclipsing binaries. For the very brightest stars, such as α Cen, Procyon, and Capella, the saturation is too severe even for halo photometry. We therefore also present preliminary work on forward modelling the TESS detector by simultaneously fitting the PSF, intra-pixel sensitivity, and flux. We aim to achieve high-precision photometry using this method to detect variability and rule out transiting exoplanets at the ppm level.