Roques by wanghonghx

VIEWS: 5 PAGES: 19

									                                     Campaign of research of
                                     small Kuiper Belt objects
                                      by stellar occultations
     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




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


KBO Workshop, DPS 2003
                    The shadow of the Kuiper Belt Objects



                                                               Circular 1km KBO




                                                                 Elliptical 1km KBO




                                                        Roques and Moncuquet, 2000

KBO Workshop, DPS 2003
                         Occultation profiles for
                             different stars




                                      QuickTime™ et un décomp resseur
                                     Anima tion sont re quis pour visu aliser
                                                  cette ima ge.




KBO Workshop, DPS 2003
                         Amplitude variation of the stellar flux
                           R* < Fresnel scale = √ (D/2)




                                                                   Roques and Moncuquet, 2000




KBO Workshop, DPS 2003
                         Amplitude variation of the stellar fux
                                 R* > Fresnel scale




                                                                  Roques and Moncuquet, 2000




KBO Workshop, DPS 2003
                           The detection of diffracting occultations
                                            needs
                            High speed photometric observations



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

         •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




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

           •Method :     cumulative observations
                         homogeneous data processing=>4- events
                         comparison with estimations


                         •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)



KBO Workshop, DPS 2003
                                Observations PIC 2000
                                      T2m data




               Stellar flux




                     (5 mn)



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

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 observations
                                                      and
                                            •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=4

                                                   q=3




                                                             log(depth)

KBO Workshop, DPS 2003
                             COROT
                                             Astéroseismology Field of Corot

                                     High précision photometry
                                     dt = 1 second:

                                       M          6               8         12
                                    Sigm a        4.10-4          10-3      6.10-3

                                                    60 meters objects are détectable
                                    i=0°
                                     = 80°
                                    10 days
                                    4- détections => 6 to 50 KBO
                                    8 stars : 1 O5 - m=6 r = 60 m           2-30 objects
     Launch : 2005                            3 F5 - m=8 r = 250 m          2-12 objects
                                              4 F5 - m=12 r = 100 m         2-12 objects




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


KBO Workshop, DPS 2003
                                       Prospective
                                      -chromaticity-


                                                                          = 0.4m




                                                                          = 1.2m




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

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


KBO Workshop, DPS 2003
                                   Prospective :
                             8 meters telescope - space


                                                            Fast phtometry
                                                            20-100 Hz
                                                            needed!




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


                  Information on the size and distance of the KBO

KBO Workshop, DPS 2003
                                 Prospective
                         Distants 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


KBO Workshop, DPS 2003

								
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