Multiwavelength calibration of the Pierre Auger Observatory fluorescence detectors and its effect on reconstructed parameters

The fluorescence detector of the Pierre Auger Observatory is sensitive to primary particle composition of cosmic rays through the measurement of the depth of shower maximum, X$_{max}$. X$_{max}$ as a function of energy, or the elongation rate, depends on the primary particle composition, and any uncertainty in the X$_{max}$ measurement could lead to a bias in the interpretation of the elongation rate. One uncertainty may arise from how the detector efficiency is calibrated as a function of wavelength. The calibration of the Pierre Auger Observatory fluorescence detector is performed using a uniform 2.5m diameter light source that allows for an end-to-end measurement of all detector components. The multiwavelength calibration utilizes the 2.5m diameter light source where the output of a xenon flasher is fed into a monochromator and the monochromator selects single wavelengths across the nitrogen fluorescence spectrum to measure the efficiency of the detector. A recent change in fluorescence detector efficiency altered the energy scale of the Pierre Auger Observatory by 4\%. Presented here is the effect on X$_{max}$ due to the above change in efficiency and preliminary results from a more detailed multiwavelength calibration and its effects on energy reconstruction and X$_{max}$.