1. workshop 3ieme zone 11-12 janvier 2007 1 Serendipitous stellar occultations and the structure of the Kuiper Belt F. Roques, A. Doressoundiram (Observatoire de Paris) G. Georgevits (UKST, Australia) V. Dhillon (Sheffield U., UK) 1976 : An idea (Bailey) 2000 : A theory (Roques et al.) 2000-2006 :Various observational approaches : 1 - King et al. : american-taiwan project with four automatic small telescopes TAOS 2 - Roques et al. : ultra rapid camera on large telescopes WHT-VLT 3 - Alcock et al. : american project of spatial mission Whipple 2006 : Three simultaneous detections : - Chang et al.(Nature 2006) : Scorpius X1 : RXTE58 detections - Georgevits (in press) : 100 hot stars: UKSThundreds detections - Roques et al. (AJ, 2006) : 2 very hot stars :WHT+VLT 3 detections

2. workshop 3ieme zone 11-12 janvier 2007 2 Serendipitous stellar occultations : What ? detection of the shadow of kbo to scan invisible small and far populations Why ? :  the perturbation of under-kilometer kbo on occulted star flux can be detectable How ? fast photometry (>40 hz) Where ? : target stars with small angular size

3. workshop 3ieme zone 11-12 janvier 2007 3 A diffracting phenomenon Roques and al., 2000 R=1 km @ 40 UA

4. workshop 3ieme zone 11-12 janvier 2007 4 The Fresnel scale F = √(.R/2) : wavelength R: distance of the kbo R = 3 AU, Fs = 0.245 km R = 40 AU, Fs = 1.1 km R = 10 5 AU, Fs = 55 km The Fresnel scale is the scaling factor of the occultation Roques et al., 2000

5. workshop 3ieme zone 11-12 janvier 2007 5 Occultation profiles for different sized stars

6. workshop 3ieme zone 11-12 janvier 2007 6 High speed photometric observations The noise limits the possibility to detect an occultation event  => detectable KBO 0.1 => 430 meters KBOone meter telescope 0.01=> 120 meters KBOfour meters telescope 0.001=> 40 meters KBOspace

7. workshop 3ieme zone 11-12 janvier 2007 7 The distance of the kbo Roques et al., 1987, AJ, 93-6, 1549

8. workshop 3ieme zone 11-12 janvier 2007 8 The large telescope campaign 2004-2005 William Herschel Telescope, Canary Islands (4 meters) ULTRACAM is an ultra-fast, triple-beam CCD camera which has been designed “to study one of the few remaining unexplored regions of observational parameter space - high temporal resolution” (V. Dhillon). - 3 successive fields of 2 stars (O stars) par night - 3 wavelengths (u’: 0.36  m, g’:0.48  m and i’:0.77  m) - 44 Hz

9. workshop 3ieme zone 11-12 janvier 2007 9 The large telescopes campaign Roques et al.,AJ, august 2006, 132, 819 35 hours of data => 3 detections

10. workshop 3ieme zone 11-12 janvier 2007 10 The large telescopes campaign : distance between 100 UA and 200 UA (da = 1 UA) radius between 0 and 400 m (d  = 20 m) 0.028 one solution : - 320  20 meters radius - 140  1 AU distance

11. workshop 3ieme zone 11-12 janvier 2007 11 The UKST campaign University of New South wales, Australia UKST : - 70 hours of data - 100 stars - = 0.4-0.8  m - Hundreds of events - No diffraction fringes Georgevits, in press

12. workshop 3ieme zone 11-12 janvier 2007 12 The UKST campaign Georgevits, in press

13. workshop 3ieme zone 11-12 janvier 2007 13 First comparison of the UKST and the WHT results * : WHT data  : UKST data 0.2 0.3 0.70.5 odk radius (Fs)

14. workshop 3ieme zone 11-12 janvier 2007 14 COROT

15. workshop 3ieme zone 11-12 janvier 2007 15 Serendipitous stellar occultations and the structure of the Kuiper Belt First indications about the Kuiper Belt Structure : A large population of small kbo : 10 10 - 10 11 odk/d 2 Extended cold disk beyond 50-200 AU Cumulative size distribution index : q = 1.3 ? Future : spatial structure of the disk size distribution of the objects shape - binarity