The encircled energy function of the IXPE determined from data of the crab pulsar

The Imaging X-ray Polarimetry Explorer (IXPE) is the unprecedented satellite capable of obtaining the x-ray polarization map. To obtain the accurate polarization map for extended sources, the measurements of the Encircled Energy Function (EEF) in flight is necessary. Though it has been often carried out using point-like source, the background may affect the accurate measurements. So, we have investigated the EEF using the data of the Crab pulsar with the nebula, because the background can be accurately removed by subtracting the off-pulse component from the on-pulse component. With the method, we succeeded in obtaining the energy dependence of the EEF.