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Serendipitous stellar occultations and the structure of the Kuiper Belt

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.)

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Serendipitous stellar occultations and the structure of the Kuiper Belt

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  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 : RXTE 58 detections - Georgevits (in press) : 100 hot stars : UKST hundreds detections - Roques et al. (AJ, 2006) : 2 very hot stars :WHT+VLT 3 detections 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 workshop 3ieme zone 11-12 janvier 2007

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

  4. The Fresnel scale The Fresnel scale is the scaling factor of the occultation F = √(.R/2) • : wavelength R: distance of the kbo • R = 3 AU, Fs = 0.245 km • R = 40 AU, Fs = 1.1 km • R = 105 AU, Fs = 55 km Roques et al., 2000 workshop 3ieme zone 11-12 janvier 2007

  5. Occultation profiles for different sized stars 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 KBO one meter telescope • 0.01 => 120 meters KBO four meters telescope • 0.001 => 40 meters KBO space workshop 3ieme zone 11-12 janvier 2007

  7. The large telescope campaign 2004-2005 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). William Herschel Telescope, Canary Islands (4 meters) - 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 workshop 3ieme zone 11-12 janvier 2007

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

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

  10. The UKST campaignUniversity 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 workshop 3ieme zone 11-12 janvier 2007

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

  12. First comparison of the UKST and the WHT results * : WHT data  : UKST data 0.2 0.3 0.5 0.7 odk radius (Fs) workshop 3ieme zone 11-12 janvier 2007

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

  14. Serendipitous stellar occultations and the structure of the Kuiper Belt First indications about the Kuiper Belt Structure : • A large population of small kbo : 1010 - 1011 odk/d2 • 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 workshop 3ieme zone 11-12 janvier 2007

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