Millisecond dips in the 2007-2009 RXTE/PCA lightcurve of Sco X-1 and one possible occultation event

Serendipitous stellar occultation search is so far the only way to detect the existence of very small, very dim, remote objects in the solar system. To date, however, there are only very few reported detections for trans-Neptunian objects (TNOs) in optical bands. In the X-ray band, with the RXTE/PCA data of Sco X-1 taken from June 2007 to October 2009, we found one possible X-ray occultation event. We discuss the veracity and properties of this event, and suggest upper limits to the size distribution of TNOs at hectometer size and of Main-Belt Asteroids (MBAs) at decameter size.