Fringing analysis and forward modeling of Keck Planet Imager and Characterizer (KPIC) spectra

The Keck Planet Imager and Characterizer (KPIC) combines high contrast imaging with high resolution spectroscopy (R∼35,000 in K band) to study directly imaged exoplanets and brown dwarfs in unprecedented detail.KPIC aims to spectrally characterize substellar companions through measurements of planetary radial velocities, spins, and atmospheric composition.Currently, the dominant source of systematic noise for KPIC is fringing, or oscillations in the spectrum as a function of wavelength.The fringing signal can dominate residuals by up to 10% of the continuum for high S/N exposures, preventing accurate wavelength calibration, retrieval of atmospheric parameters, and detection of planets with flux ratios less than 1% of the host star.To combat contamination from fringing, we first identify its three unique sources and adopt a physically informed model of Fabry-Pérot cavities to apply to post-processed data.We find this strategy can effectively model the fringing in observations