Absolute photometric calibration of the infrared camera (IRC) aboard AKARI

The absolute photometric calibration of imaging observations with the Infrared Camera (IRC) aboard the AKARI satellite was performed by monitoring the same stars regularly and by observing a set of standard stars. By our monitoring observations, we confirmed that all channels of the IRC were stable to within 4% and that their sensitivities were constant until the liquid helium was exhausted. Using the data of these repeated observations, we evaluated the intrinsic errors as a function of the brightnesses of objects and found that the errors increase rapidly toward fainter objects. We also checked the consistency between short and long exposure times, and confirmed that the data sampling had been executed as designed. Finally, by comparing the estimated in-band flux densities and the observed data values of standard stars, we obtained conversion factors to the absolute flux densities of all the band/exposure configurations. Their absolute uncertainties are estimated to be less than 6%.