KBO Workshop, DPS 2003

Campaign of research of Campaign of research of small Kuiper Belt objects small Kuiper Belt objects

by stellar occultationsby stellar occultations

• - Stellar occultations are diffracting phenomena• - A powerful tool to accede to invisible small KBO• - First results of the Pic du Midi campaign• - Prospective projects

Roques, F., (1), Doressoundiram A. (1), Moncuquet M. (1), Chevreton M. (1), Colas, F. (2), Lecacheux, J.(1), Auvergne, M.(1)GP Tozzi (3), O. Hainault (4)

(1) LESIA, Observatoire de Paris, 92195 Meudon (France)(2) IMCCE, Observatoire de Paris, 92195 Meudon (France)(3) Oss. Astrofisico di Arcetri, Firenze (Italy)(4) European Southern Observatory

KBO Workshop, DPS 2003

The shadow of the Kuiper Belt Objects

Roques and Moncuquet, 2000

Circular 1km KBO

Elliptical 1km KBO

KBO Workshop, DPS 2003

Occultation profiles for different stars

QuickTime™ et un décompresseurAnimation sont requis pour visualiser

cette image.

KBO Workshop, DPS 2003

Amplitude variation of the stellar fluxR* < Fresnel scale = √ (D/2)

Roques and Moncuquet, 2000

KBO Workshop, DPS 2003

Amplitude variation of the stellar fuxR* > Fresnel scale

Roques and Moncuquet, 2000

KBO Workshop, DPS 2003

The detection of diffracting occultationsneeds

High speed photometric observations

•The noise (scintillation) limits the possibility to detect an occultation event•The simulations => depth of the occultation profiles•A 4 deep event is detectable

• => detectable KBO•0.01 => 120 meters KBO•0.001 => 40 meters KBO

The velocity of the KBO in the sky plane toward the opposition : 25 km/sec=> Fast photometry (20 hz) is necessary

KBO Workshop, DPS 2003

Occultations rates

TAOS

T4M

T8M

space

KBO Workshop, DPS 2003

Telescopes sizes and constraint on q

•The noise is due to scintillation: = S0 .d-2/3.X3/2.e-h/H0.(2 )-1/2

T2M : =0.02

T4M : =0.01

T8M : =0.001

KBO Workshop, DPS 2003

Observations PIC 2000-2003

•2 telescopes: T-2m and T-1m•Multi-objects photometers:

- a target star- a comparison star- sky

•Ecliptic latitude = 0.2 °- r* =50m•20 Hz•09/2000(7 nights) +03/2003 (7 nights)

•Method : cumulative observations homogeneous data processing=>4- eventscomparison with estimations

KBO Workshop, DPS 2003

Observations PIC 2000T2m data

•15 hours of data with better than 0.02 (T-2m) and = 0.027 (T-1m)

Stellar flux

(5 mn)

KBO Workshop, DPS 2003

Observations PIC 2003

•12 hours of data with better than 0.02 (T-2m)

KBO Workshop, DPS 2003

Observations PIC 2000-2003

•27 hours of observationsand

•4- level of detection=>

•Estimation of occultation rate : 0.4 (q = 3) 2 (q = 4) 4 (q = 4.5)

0 detection

KBO Workshop, DPS 2003

Observations PIC 2000-2003

A potential event (3-) compatible with a 150 meter KBO

q = 3

q = 4

log(depth)

log(

rate

)

KBO Workshop, DPS 2003

COROT

Astéroseismology Field of Corot

• High précision photometry• dt = 1 second:

M 6 8 12Sigma 4.10-4 10-3 6.10-3

60 meters objects are détectablei=0°Ω = 80°10 days4-σ détections => 6 to 50 KBO8 stars : 1 O5 - m=6 r = 60 m 2-30 objects

3 F5 - m=8 r = 250 m 2-12 objects4 F5 - m=12 r = 100 m 2-12 objects

Launch : 2005

EDDINGTON (one month) : hundreds of KBO, 15 m - 5 km

KBO Workshop, DPS 2003

Prospective-chromaticity-

= 0.01 (4.m telescope) - r = 100 m

= 0.4m

= 1.2m

Information on the Fresnal scale, then, on the distance of the KBO

KBO Workshop, DPS 2003

Prospective : 8 meters telescope - space

= 0.001 (8-m telescope) - r = 40m

Information on the size and distance of the KBO

Fast phtometry 20-100 Hzneeded!

KBO Workshop, DPS 2003

ProspectiveDistants objects : Oort cloud

A 4 km Oort cloud object at 10 4 AU

KBO Workshop, DPS 2003

Future projects

•Campaign on the TBL telescopes

•Larges telescopes => pb : fast photometry

•Technical data : guiding cameras ESO-VLT

•Space : Corot, Eddington, dedicated instrument

KBO Workshop, DPS 2003

Conclusions

• Stellar occultations give a zoom on planétésimals :kilometer and sub-kilometer Kuiper Belt objects

• Diffracting occultations are accessible from ground-based telescopes

• Campaign on Pic du Midi 2000-2003 :• zero 4 event on 27 h => first constraint on q • one potentiel event (150 meters KBO)

• Large Telescopes + fast photometry (20 hz) =>???

•Space : high precision photometry missions (Corot - Eddington)

Dedicated instrument/mission