31st Annual Meeting of the DPS, October 1999
Session 26. Edgeworth-Kuiper Belt II
Contributed Oral Parallel Session, Tuesday, October 12, 1999, 10:30-11:20am, Sala Pietro d'Abano

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[26.05] Detection of the Kuiper Belt by Stellar Occulatiion: I

F. Roques, M. Moncuquet (DESPA, Observatoire de Paris, France)

The existence of a residual protoplanetary disk beyond the Neptune orbit had been speculated by Kuiper and the recent discovery of hundreds of objects above 30 AU confirms the reality of the Kuiper hypothesis. The Kuiper Disk could include a huge number of kilometer sized objects. The knowledge of this small Kuiper Belt Objects (KBOs) population is a key problem because it could contain most of the Kuiper disk mass. Stellar occultations are known to be a powerful tool to explore the Outer Solar System and they led to the discovery of the Uranus and Neptune rings systems.

We explore the possibility to detect KBOs by statistical (i.e. unpredictable) occultations: In a companion paper, we show that such occultations are diffraction phenomenon and that it is possible to exploite this phenomenon to optimize the detection of KBOs with high precision photometric observations, and we focus here on the expected conditions of such observations.

We estimate the occultation rate of a star by KBOs with the hypothesis that the size distribution in the Belt continues from the observed objects until the sub-kilometers ones. The occultation rate depends on: \\ - the direction of observation which governs the velocity of the KBO in the sky plane. \\ - the star itself, because the size of the KBOs detectable by occultation is of the order of the size of the star. A O5 star of mV=11 has a projected radius of 0.2 km. For the same magnitude, a M5 star has a projected radius of 10 km. \\ - the photometric precision of the observation.

The occultation rate per night for one star goes from 10-6 to several tens depending on the star and on the photometric precision of the observation. As the occultation by a KBO lasts a fraction of second, high speed photometric observation is necessary with a frequency of 1 Hz to 20 Hz. We present also possible methods to discriminate occultations by KBO from occultations by asteroids and comets.

The author(s) of this abstract have provided an email address for comments about the abstract: roques@obspm.fr

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