CCD observations: rotational properties of 13 small asteroids

About 10 years ago our group in the Meudon Observatory started an observational program on small asteroids (diameter ⩽ 50 km) in order to enlarge the knowledge of this size range objects. The results of three observational runs are reported, carried out in January 1993, August 1993 and August 1994, with the 1.2 m telescope of the Haute-Provence Observatory and with the 2.0 m telescope of the Pic du Midi Observatory, both in France. Thirteen asteroids were observed; for 9 of them the rotational period was determined with different quality codes and the composite lightcurves obtained are presented. For four asteroids (3017 Petrovic (Psyn = 4.069±0.006 h), 4045 1953RG (Psyn = 9.764±0.003 h), 4483 Petofi (Psyn = 4.480±0.013 h) and 4628 Laplace (Psyn = 9.011±0.005 h)) an unambiguous period is determined. For three of them (4224 Susa (Psyn = 7.78±0.01 h), 4423 1949GH (Psyn = 10.51±0.01 h), and 5104 1986RU5 (Psyn = 6.14±0.01) a reasonably secure result is obtained. For two (3485 Barucci (Psyn = 14.65±0.06 h) and 3909 Gladys (Psyn = 6.83±0.01 h)) a tentative result is given. For the others (1783 Albitskij, 4164 Shilov, 4232 1977CD, and 4867 Polites) the single-night lightcurves are reported.