A study of asteroid polelatitude distribution based on an extended set of shape models derived by the lightcurve inversion method
Abstract
Context. In the past decade, more than one hundred asteroid models were derived using the lightcurve inversion method. Measured by the number of derived models, lightcurve inversion has become the leading method for asteroid shape determination.
Aims: Tens of thousands of sparseintime lightcurves from astrometric projects are publicly available. We investigate these data and use them in the lightcurve inversion method to derive new asteroid models. By having a greater number of models with known physical properties, we can gain a better insight into the nature of individual objects and into the whole asteroid population.
Methods: We use sparse photometry from selected observatories from the AstDyS database (Asteroids  Dynamic Site), either alone or in combination with dense lightcurves, to determine new asteroid models by the lightcurve inversion method. We investigate various correlations between several asteroid parameters and characteristics such as the rotational state and diameter or family membership. We focus on the distribution of ecliptic latitudes of pole directions. We create a synthetic uniform distribution of latitudes, compute the method bias, and compare the results with the distribution of known models. We also construct a model for the longterm evolution of spins.
Results: We present 80 new asteroid models derived from combined data sets where sparse photometry is taken from the AstDyS database and dense lightcurves are from the Uppsala Asteroid Photometric Catalogue (UAPC) and from several individual observers. For 18 asteroids, we present updated shape solutions based on new photometric data. For another 30 asteroids we present their partial models, i.e., an accurate period value and an estimate of the ecliptic latitude of the pole. The addition of new models increases the total number of models derived by the lightcurve inversion method to ~200. We also present a simple statistical analysis of physical properties of asteroids where we look for possible correlations between various physical parameters with an emphasis on the spin vector. We present the observed and debiased distributions of ecliptic latitudes with respect to different size ranges of asteroids as well as a simple theoretical model of the latitude distribution and then compare its predictions with the observed distributions. From this analysis we find that the latitude distribution of small asteroids (D < 30 km) is clustered towards ecliptic poles and can be explained by the YORP thermal effect while the latitude distribution of larger asteroids (D > 60 km) exhibits an evident excess of prograde rotators, probably of primordial origin.
Tables 36 are available in electronic form at http://www.aanda.org
 Publication:

Astronomy and Astrophysics
 Pub Date:
 June 2011
 DOI:
 10.1051/00046361/201116738
 arXiv:
 arXiv:1104.4114
 Bibcode:
 2011A&A...530A.134H
 Keywords:

 minor planets;
 asteroids: general;
 thechniques: photometric;
 methods: numerical;
 methods: statistical;
 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 16 pages, 12 figures, 6 tables, accepted for publication in Astronomy &