31st Annual Meeting of the DPS, October 1999
Session 24. Asteroids: Yarkovsky Effect and Collisions
Contributed Oral Parallel Session, Tuesday, October 12, 1999, 10:30am-12:00noon, Sala Plenaria

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[24.07] The Spin Vector Distribution of Main Belt Asteroids

A. Erikson (DLR, Berlin)

The large main belt asteroids have been formed during an accretion process where their original physical properties (e.g. spin state) depended on the medium they formed from and the details of the growth mechanism. In this context the spin vector of an asteroid is an important property since it is closely linked to the general evolution of the main belt.

New photometric observations have been acquired for 42 main belt asteroids in order to determine a substantial data set of reliable spin vectors. In combination with already existing lightcurves, the observational data yielded models of the spin vectors for 46 asteroids using standard computing procedures. Together with previously published models the new data set consists of spin vector parameters for 73 main belt asteroids. Compared to previous studies, this data set represents a doubling of asteroids with known spin vectors and is close of being complete for the largest objects (D>200 km). The spin vector distribution has following basic properties:

There exists a significant dominance of asteroids with a prograde sense of rotation and with their spin vectors concentrated towards the north ecliptic pole.

A comparison of the spin vector distribution between asteroids with different diameters reveals three specific zones. The large asteroids (D>200 km) for which the spin vectors are moderately anisotropic. An intermediate size range (D~70-150 km) including objects with the strongest spin vector concentration toward the north ecliptic pole and the smaller asteroids with a completely isotropic distribution.

There exists a strong correlation between the spin vector distribution and the orbital inclination of the studied asteroids.

Variations in the spin vector distribution are present between asteroids of different taxonomic types.

The above results will be interpreted in an evolutionary scenario for the main belt population.

The author(s) of this abstract have provided an email address for comments about the abstract: Anders.Erikson@dlr.de

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