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

TL;DR

This study used a novel high-speed photometry technique to search for occultations of bright stars by small Kuiper Belt Objects, setting new upper limits on their sky density without detecting any occultations.

Contribution

It introduces a new high-precision, high-speed photometry method using Megacam in shutterless mode for occultation surveys of the outer solar system.

Findings

No occultations detected in 220 star hours.

Set upper limits on KBO surface density for objects larger than 0.7 km and 1 km.

Achieved over 10% survey efficiency for KBOs ≥0.7 km.

Abstract

We conducted a search for occultations of bright stars by Kuiper Belt Objects (KBOs) to estimate the density of sub-km KBOs in the sky. We report here the first results of this occultation survey of the outer solar system conducted in June 2007 and June/July 2008 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. We present an analysis of 220 star hours at signal-to-noise ratio of 25 or greater. The survey efficiency is greater than 10% for occultations by KBOs of diameter d>=0.7 km, and we report no detections in our dataset. We set a new 95% confidence level upper limit for the surface density \Sigma_N(d) of KBOs larger than 1 km: \Sigma_N(d>=1 km) <= 2.0e8 deg^-2, and for KBOs larger than 0.7 km \Sigma_N(d>= 0.7 km) <= 4.8e8 deg^-2.