Hsiang-Kuang Chang (National Tsing Hua University, Taiwan)

Search for small Trans-Neptunian Objects with serendipitous occultation in X-rays

Trans-Neptunian Objects (TNOs) of kilometer size or smaller are too dim to be obseved directly. Their
population properties such as the size distribution, however, carry important information of how our planetary
system was formed in the early history of the solar system. Optical and X-ray stellar occultation caused by
small TNOs has been being exploited as a way to detect their existence, although no definite results ahve
been obtained. In X-rays, Sco X-1 is the only source bright enough for this study with RXTE. Thanks to its
large effective area, LOFT will be able to perform a larger scale of serendipitous X-ray occultation search on
a dozen of background target sources, which are located at different ecliptic latitudes. These background
targets are all Z-sources, Atoll-sources, or black-hole-candidate X-ray binaries. Their long-term monitoring
observation with LOFT will not only yield results on the TNO size distribution down to decameter size, which
is not attainable by any other means known to date, but also fit LOFT's original scientific goals on physics of
extremely high density and extremely strong gravity very well.