Development of flat fielding method in MIR for accurate photometry with TAO/MIMIZUKU

‘Field Stacker’ is a unique system mounted on MIMIZUKU, a mid-infrared instrument for the TAO 6.5-m telescope. This system obtains a pair of distant targets simultaneously and aims at performing relative photometry with an accuracy of a few percent. A key to achieve the accurate relative photometry is precise flat fielding. We have developed a new method for the flat fielding using time variation of the sky background. We analyzed the data obtained in an engineering observation at the Subaru in 2018. The error of the flat fielding and the total error propagated from the flat fielding are estimated to be 0.2–0.3% and 0.5%, respectively.