Photometry and models of selected main belt asteroids. VIII. Low-pole asteroids

Context. The set of more than 100 asteroids, for which spin parameters have been modelled using an amplitude, magnitude or epoch methods, showed a pronounced gap in the distribution of the asteroid spin axes. These spin axes are rarely aligned with the ecliptic plane.
Aims: The number of asteroids with known spin parameters should be increased to allow for statistical investigations.
Methods: We gathered extensive photometric datasets on four selected main-belt asteroids to model their spin and shape parameters using the lightcurve inversion method. Our only criterion of selection was their observability for small telescopes.
Results: All four of the modelled asteroids happened to have rotational poles that lie close to the ecliptic plane (periods and J2000 north pole coordinates): (94) Aurora - P = 7.226191 h, λ_p1 = 58°, β_p1 = + 16°; λ_p2 = 242°, β_p2 = + 4°; (174) Phaedra - P = 5.750249 h, λ_p = 265°, β_p = + 5°; (679) Pax - P = 8.456016 h, λ_p1 = 42°, β_p1 = -5°; λ_p2 = 220°, β_p2 = + 32° (pole 2 preferred after comparison with AO-resolved observations); (714) Ulula - P = 6.998376 h, λ_p1 = 42°, β_p1 = -9°; λ_p2 = 227°, β_p2 = -14°.
Conclusions: This work suggests that asteroid spin axes do not avoid the ecliptic plane, contrary to what the classical modelling suggested.

Composite lightcurves (Figs. 1-26), and aspect data (Table 1) are only available in electronic form at http://www.aanda.orgPhotometric data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/529/A107