CCD photometry and new models of 5 minor planets

We present new R filtered CCD observations of 5 faint and moderately faint asteroids carried out between October, 1998 and January, 1999. The achieved accuracy is between 0.01–0.03 mag, depending mainly on the target brightness. The obtained sinodic periods and amplitudes: 683 Lanzia – 4. h6±0. 2, 0.13 mag; 725 Amanda – > 3. 0, ≥0.40 mag; 852 Wladilena – 4. h62±0. 01, 0.32 mag (December, 1998) and 0.27 mag (January, 1999); 1627 Ivar – 4. 80 ± 0. 01, 0.77 mag (December, 1998) and 0.92 mag (January, 1999). The Near Earth Object 1998 PG unambiguously showed doubly-periodic lightcurve, suggesting the possibility of a relatively fast precession (P1=1. 3, P2=5. 3). Collecting all data from the literature, we determined new models for 3 minor planets. The resulting spin vectors and triaxial ellipsoids have been calculated by an amplitude-method. Sidereal periods and senses of rotation were calculated for two asteroids (683 and 1627) by a modified epoch-method. The results are: 683 – λp = 15/195 ± 25◦, βp = 52 ± 15◦, a/b = 1.15 ± 0.05, b/c = 1.05 ± 0.05, Psid=0. d1964156±0. 0000001, retrograde; 852 – λp = 30/210±20◦, βp = 30±10◦, a/b = 2.3±0.3, b/c = 1.2± 0.2; 1627 – λp = 145/325± 8◦, βp = 34± 6◦, a/b = 2.0± 0.1, b/c = 1.09± 0.05, Psid=0. d1999154±0. 0000003, retrograde. The obtained shape of 1627 is in good agreement with radar images by Ostro et al. (1990).