A SEARCH FOR SUB-km KUIPER BELT OBJECTS WITH THE METHOD OF SERENDIPITOUS STELLAR OCCULTATIONS

The results of a search for sub-km Kuiper Belt Objects (KBOs) with the method of serendipitous stellar occultations are reported. Photometric time series were obtained on the 1.8 m telescope at the Dominion Astrophysical Observatory (DAO) in Victoria, British Columbia, and were analyzed for the presence of occultation events. Observations were performed at 40 Hz and included a total of 5.0 star-hours for target stars in the ecliptic open cluster M35 (β = 0.9°), and 2.1 star-hours for control stars in the off-ecliptic open cluster M34 (β = 25.7°). To evaluate the recovery fraction of the analysis method, and thereby determine the limiting detectable size, artificial occultation events were added to simulated time series (1/f scintillation-like power spectra), and to the real data. No viable candidate occultation events were detected. This limits the cumulative surface density of KBOs to 3.5 × 1010 deg−2 (95% confidence) for KBOs brighter than mR = 35.3 (larger than ∼860 m in diameter, assuming a geometric albedo of 0.04 and a distance of 40 AU). An evaluation of trans-Neptunian object (TNO) occultations reported in the literature suggests that they are unlikely to be genuine, and an overall 95% confidence upper limit on the surface density of 2.8 × 109 deg−2 is obtained for KBOs brighter than mR = 35 (larger than ∼1 km in diameter, assuming a geometric albedo of 0.04 and a distance of 40 AU) when all existing surveys are combined.