The IMACS Occultation Survey: I. Pilot Study

We report the results of a pilot study, searching for occultations ofbackground stars by small (sub-km) Kuiper belt objects (KBOs). Ourstudy is ground-based, using the Inamori Magellan Areal Camera andSpectrograph (IMACS) instrument on the 6.5m Magellan Baade telescope,at Las Campanas Observatory in Chile. We implemented a novelshutterless continuous readout mode on the IMACS instrument, withcustom-made aperture masks, permitting simultaneous high-speed (36 Hz)photometry for numerous stars, while minimizing the effects of stellarcrowding and sky background. Observing in the southern hemisphereallows us to target the intersection of the ecliptic and galacticplanes, where hundreds of stars can be monitored with a single fieldof view. We observed for a total of ~28 hours spread over eightnights, obtaining ~11,000 star-hours of light curves with per-pointSNR > 10. This represents an order of magnitude increase in star-hourscompared to the previous best ground-based survey by Bianco etal. (2009). Our results allow us to place strong constraints on the surfacedensity of sub-km objects in the Kuiper-Belt, as well as to complement theHST FGS results of Schlichting et al. (2009, 2012).