CHIMERA Occultation Constraints on the Abundance of Kilometer-scale Kuiper Belt Objects

Abstract

Occultations provide indirect sensitivity to the number density of small Kuiper Belt objects (KBOs) too faint to directly detect telescopically. We present results from the Caltech HI-speed Multicolor camERA (CHIMERA) survey with the Palomar Hale Telescope, which monitored stars over the central $5^{\prime} \times 5^{\prime} $ of the M22 globular cluster along the ecliptic plane for serendipitous occultations by kilometer-scale KBOs over 63 hr across 24 nights at a 33 Hz frame rate simultaneously in $i^{\prime} $ and $g^{\prime} $ . We adapted dense-field photometry and occultation template fitting techniques to this data set, finding a 95% confidence upper limit on the occultation rate, corresponding to an ecliptic sky density of ≲10 ^7 deg ^−2 of >1 km diameter classical KBOs. We discuss a few of the occultation-like light curve signatures at the edge of the sensitivity limit responsible for setting the upper bounds, and their likely nonviability as true occultations.

Keywords

• Kuiper Belt
• Multi-color photometry
• Stellar occultation