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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.) - PowerPoint PPT Presentation
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workshop 3ieme zone 11-12 janvier 2007
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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 TAOS2 - Roques et al. : ultra rapid camera on large telescopes
WHT-VLT3 - 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
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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
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A diffracting phenomenon
Roques and al., 2000
R=1 km @ 40 UA
workshop 3ieme zone 11-12 janvier 2007
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The Fresnel scale
F = √(.R/2)
: wavelengthR: distance of the kbo
• R = 3 AU, Fs = 0.245 km• R = 40 AU, Fs = 1.1 km• R = 105 AU, Fs = 55 km
The Fresnel scale is the scaling factor of the occultation
Roques et al., 2000
workshop 3ieme zone 11-12 janvier 2007
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Occultation profiles for different sized stars
workshop 3ieme zone 11-12 janvier 2007
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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
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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
workshop 3ieme zone 11-12 janvier 2007
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The large telescopes campaign
Roques et al.,AJ, august 2006, 132, 819
35 hours of data=> 3 detections
workshop 3ieme zone 11-12 janvier 2007
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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
workshop 3ieme zone 11-12 janvier 2007
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The UKST campaignUniversity of New South wales, Australia
UKST : - 70 hours of data - 100 stars- = 0.4-0.8m- Hundreds of events- No diffraction fringes
Georgevits, in press
workshop 3ieme zone 11-12 janvier 2007
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The UKST campaign
Georgevits, in press
workshop 3ieme zone 11-12 janvier 2007
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First comparison of the UKST and the WHT results
* : WHT data
: UKST data
0.2 0.3 0.70.5odk radius (Fs)
workshop 3ieme zone 11-12 janvier 2007
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COROT
Asteroseismology Field of Corot • High précision photometry • Several stars :
M 6 8 12 Sigma 4.10-4 10-3 6.10-3
60 meters objects detectable with stellar occultations i=0°
= 80° 10 days 4 detections 8 stars : 1 O5 - m=6 r = 60 m 2-30 objects 3 F5 - m=8 r = 250 m 2-12 objects 4 F5 - m=12 r = 100 m 2-12 objects
workshop 3ieme zone 11-12 janvier 2007
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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 disksize distribution of the objectsshape - binarity