Abstract
Trans-Neptunian objects (TNOs) are the witnesses of the formation of the planets during the dynamical and collisional period of our solar system. The population characteristics of sub-kilometer TNOs may carry some impor- tant clues for the origin of the planets. However, the knowledge of them is far from enough, particularly for those smaller ones, due to very few detections. Nowadays only TNOs larger than about 25 km can be directly observed. For the TNOs not able to be directly observed, searching for serendipitous stellar occultation events is a possible method. Several serendipitous searches were proceeded, but so far there are only two possible detections from archival data of Hubble Space Telescope by Schlichting et al. in 2009 and 2012. My thesis work is going to search for more sub-kilometer sized TNOs by applying the serendipitous occultation method. The search is divided into two major parts: in X-rays and in Optical bands. The X-rays observations are all from the RXTE (Rossi X-rays Timing Explorer) satellite, and the Optical observations are from COROT (Convection Rotation and Planetary Transits) satellite and MIOSOTYS (Multi-object Instrument for Occultation in the SO- lar system and TransitorY Systems) instrument mounted on two ground-based telescopes in France and Spain. From 334-ks RXTE/PCA, no definite TNO occultation events were found. The only suspicious non-instrumental flux-drop event was not considered to be resulted from the small TNO occultation after analyzing it with the fittings of the diffraction patterns. Then we investigate the detection efficiency dependence on the TNO size to better define the sensible size range of our approach, and suggested upper limits to the TNO size distribution in the size range from 30 to 300 m. A list of X-ray sources suitable for future larger facilities to ob- serve is proposed. The total observation time employed in our COROT work is about 144408.34 star-hours with SNR larger than 1000 computed on 30-second intervals. 13 Possible Occultation Events (POEs) were found from the deviation method. These detections gives a density in the ecliptic sky plane of TNOs larger than 400-meter radius of N(R > 400m) = 1.4^{+4.2}_{-0.7} 10^7 deg^-2. The fit of the density of TNOs with the believed break r_break = 45 km provides a power-law size distribution index q larger than 3.5. This value is consistent with the detection of 2 potential events from HST/FGS observations that found q = 3.8 +- 0.2. However, fitting the 13 POEs with the HST/FGS result alone gives a power-law size distribution index of q = 4.5 +- 0.2 in the size range between 0.2 to 2.0 km. This value is then compared with evolution models of the Kuiper Belt and the results from the recent surveys of Jupiter Family Comets (JFCs). The MIOSOTYS instrument has been mounted as a visitor instrument on the 1.93-m telescope at Observatoire de Haute-Provence (OHP) in France since February 2010, and on the 1.23-m telescope at Calar Alto Observatory (CAHA) in Spain since November 2012. By July 2014, MIOSOTYS project has successfully carried out 19 observational runs. The total exposure time before screening is about 3.5 x 10^7 sec, which is about 9840 star hours, from 85 nights. For MIOSOTYS, we have developed an optimized observing strategy to search for TNOs. We have also developed in this project a new search algorithm of events by the method of fluctuations.