Katelyn Horstman (Caltech)

The Keck Planet Imager and Characterizer (KPIC) is a fiber injection unit that feeds a high-resolution spectrograph (1.9-2.5 microns, R~35,000) at the W.M. Keck Observatory. KPIC aims to spectrally characterize brown dwarfs and exoplanets through measurements of planetary radial velocities, spins, and atmospheric composition. One target accessible with KPIC is GQ Lup B, a substellar companion with a detected circumplanetary disk, or CPD. Observations of the CPD suggest the presence of a cavity, possibly formed by an exo-satellite. Using high resolution, K-band spectra from KPIC, this study reports the first dedicated exomoon radial velocity searches around the directly imaged substellar companion GQ Lup B. Over 10 epochs, we find a median RV error of 1 km/s, most likely limited by systematic fringing, or oscillations in the spectrum’s continuum as a function of wavelength due to transmissive optics in KPIC. With this RV precision, KPIC is sensitive to exomoons 2.8% the mass of GQ Lup B at a separation of 65 Jupiter radii, or the extent of the cavity measured in the CPD detected around GQ Lup B. Given previous KPIC companion sensitivities, the analysis of an additional survey focused on identifying spectroscopic brown dwarf binaries within 1 AU of their host stars is underway. By measuring companion RVs of 11 targets at least once a year for three years, this survey aims to better understand the occurrence rate and separation of these binaries as a function of mass ratio and distance to the host star. I present preliminary radial velocities for several targets between 2020 to 2025, leveraging previous KPIC observations.