Combined light High-Resolution Cross-Correlation Spectroscopy (HRCCS) uses cross-correlation with a model planetary atmosphere to identify/isolate spectral features that show a Doppler shift consistent with the motion of a close-in exoplanet. This technique can be used to retrieve molecular abundances and pressure-temperature profiles for hot Jupiters, offering insight into planet formation and atmospheric chemistry. HRCCS is quite sensitive to instrumental systematics, in particular shifts in wavelength solution, blaze function variation, uncorrected tellurics, and fringing. We discuss the on-sky performance of Keck/KPIC for HRCCS, with a focus on the impact of these systematic effects and mitigation approaches.
Vortex fiber nulling (VFN) is a single-aperture interferometric technique for detecting and characterizing exoplanets separated from their host star by less than a diffracted beam width. VFN uses a vortex mask and single-mode fiber to selectively reject starlight while coupling off-axis planet light with a simple optical design that can be readily implemented on existing direct imaging instruments that can feed light to an optical fiber. With its axially symmetric coupling region peaking within the inner working angle of conventional coronagraphs, VFN is more efficient at detecting new companions at small separations than conventional direct imaging, thereby increasing the yield of on-going exoplanet search campaigns. We deployed a VFN mode operating in K band (2.0 to 2.5 μm) on the Keck Planet Imager and Characterizer (KPIC) instrument at the Keck II Telescope. We present the instrument design of this first on-sky demonstration of VFN and the results from on-sky commissioning, including planet and star throughput measurements and predicted flux-ratio detection limits for close-in companions. The instrument performance is shown to be sufficient for detecting a companion 103 times fainter than a fifth magnitude host star in 1 h at a separation of 50 mas (1.1 λ / D). This makes the instrument capable of efficiently detecting substellar companions around young stars. We also discuss several routes for improvement that will reduce the required integration time for a detection by a factor >3.
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.
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.
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