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 of bright stars, reducing the residual systematics caused by fringing by a factor of 2. Next, we wedge two of the transmissive optics internal to KPIC to eliminate two sources of fringing and confirm the third source as the entrance window to the spectrograph. Finally, we apply our previous model of the Fabry-Pérot cavity to new data taken with the wedged optics to reduce the amplitude of the residuals by a factor of 10.
KPIC (Keck Planet Imager and Characterizer) is a series of upgrades to Keck II adaptive optics and the NIR-SPEC spectrograph enabling K-band diffraction-limited high-resolution spectroscopy. KPIC’s single-mode fibers provide a substantial reduction in sky background as well as an extremely stable line-spread function. In this paper we present the on-sky performance of KPIC phase I and lessons learned from calibration and operation of the system, including procedures for maximizing throughput and assessments of long-term line-spread and calibration stability. During phase I, KPIC successfully detected 23 exoplanets and brown dwarfs, with separations from 200 to 3600 mas and K-band magnitudes up to 17.
The Keck Planet Imager and Characterizer (KPIC) is a series of upgrades for the Keck II Adaptive Optics system and the NIRSPEC spectrograph to enable diffraction-limited, high-resolution (R>30,000) spectroscopy in the K and L bands. KPIC’s use of single-mode fibers provides a substantial reduction in sky background as well as an extremely stable line-spread function. In this paper we present the results of extensive system-level laboratory testing and characterization of Phase II of the instrument and each of its modes. We also show early on-sky results from the first few months of commissioning with these upgrades along with the next steps for the instrument.
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