The IMACS Occultation Survey: I. Pilot Study

Friday, 19 December 2014
Matthew Jon Holman1, Matthew John Payne1, Charles Alcock2, Hilke Schlichting3, David Osip4, Federica Bianco5, Brian McLeod1, Ruth Murray-Clay1, Paul Nulsen2, Pavlos Protopapas6, Ian Thompson4, Greg Burley7 and Christoph Birk4, (1)Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, United States, (2)Smithsonian Astrophysical Observatory, Cambridge, MA, United States, (3)Massachusetts Institute of Technology, Earth, Atmospheric, and Planetary Sciences, Cambridge, MA, United States, (4)Carnegie Inst Washington, Las Campanas Observatory, Washington, DC, United States, (5)New York University, Center for Cosmology and Particle Physics, New York, NY, United States, (6)Harvard University, School of Engineering and Applied Sciences, Cambridge, MA, United States, (7)NRC Canada, Herzberg Astrophysics, Victoria, BC, Canada
We report the results of a pilot study, searching for occultations of
background stars by small (sub-km) Kuiper belt objects (KBOs). Our
study is ground-based, using the Inamori Magellan Areal Camera and
Spectrograph (IMACS) instrument on the 6.5m Magellan Baade telescope,
at Las Campanas Observatory in Chile. We implemented a novel
shutterless continuous readout mode on the IMACS instrument, with
custom-made aperture masks, permitting simultaneous high-speed (36 Hz)
photometry for numerous stars, while minimizing the effects of stellar
crowding and sky background. Observing in the southern hemisphere
allows us to target the intersection of the ecliptic and galactic
planes, where hundreds of stars can be monitored with a single field
of view. We observed for a total of ~28 hours spread over eight
nights, obtaining ~11,000 star-hours of light curves with per-point
SNR > 10. This represents an order of magnitude increase in star-hours
compared to the previous best ground-based survey by Bianco et
al. (2009). Our results allow us to place strong constraints on the surface
density of sub-km objects in the Kuiper-Belt, as well as to complement the
HST FGS results of Schlichting et al. (2009, 2012).