A Search for Occultations of Bright Stars by Small Kuiper Belt Objects Using Megacam on the MMT

We conducted a search for occultations of bright stars by Kuiper Belt Objects (KBOs) to estimate the density of subkilometer KBOs in the sky. We report here the first results of this occultation survey of the outer solar system conducted in 2007 June and 2008 June/July at the MMT Observatory using Megacam, the large MMT optical imager. We used Megacam in a novel shutterless continuous-readout mode to achieve high-precision photometry at 200 Hz, which with point-spread function convolution results in an effective sampling of ∼30 Hz. We present an analysis of 220 star hours of data at a signal-to-noise ratio of 25 or greater, taken from images of fields within 3° of the ecliptic plane. The survey efficiency is greater than 10% for occultations by KBOs of diameter d ⩾ 0.7 km, and we report no detections in our data set. We set a new 95% confidence level upper limit for the surface density Σ N ( d ) of KBOs larger than 1 km: Σ N ( d ⩾ 1 km) ⩽ 2.0 × 10 8 deg −2 , and for KBOs larger than 0.7 km Σ N ( d ⩾ 0.7 km) ⩽ 4.8 × 10 8 deg −2 .