D. Riccioli

Rotational periods of asteroids II

Abstract In the framework of the photoelectric asteroid observational program undertaken at Catania University to collect lightcurves apt to apply the pole computational methods, the V-band lightcurves and the values of the synodic rotational period and of the average B–V colour index of 5 Astrea, 6 Hebe, 12 Victoria, 13 Egeria, 26 Proserpina, 34 Circe, 63 Ausonia, 66 Maja, 102 Miriam, 140 Siwa, 176 Iduna, 181 Eucaris, 241 Germania, 250 Bettina, 258 Tyche, 313 Chaldea, 335 Roberta, 352 Gisela, 419 Aurelia, 471 Papagena, 537 Pauly, 639 Latona and 984 Gretia are presented.

New rotational periods of 18 asteroids

Abstract The results of photoelectric observations of 18 main-belt asteroids are discussed. The V-band lightcurves, the B–V colors, and the values of the synodic rotational period are presented. There exists no previous determination of the period for 13 of them.

Pole and shape determinaton of asteroids. II

Abstract To update the research work on asteroids to obtain their rotation axis orientation and axes ratios, we went on implementing the collection of lightcurves. By means of new observations carried out and new lightcurves published, we were able to apply the computation methods of the rotation parameters to 18 minor planets. The found values of the pole coordinates and of the axes ratios are reported. For 14 objects, this is the first determination of these elements which are necessary to study the collisional evolution of the asteroids.

Physical studies of asteroids XXX: the asteroid 153 Hilda

The asteroid 153 Hilda was studied by photometric, spectroscopic and polarimetric observations during the apparition in 1992. The rotation period was determined to 5.11 hours with a lightcurve amplitude of 0.05 magnitudes. From our spectrum we find 153 Hilda to be of taxonomic type P. The polarization value of -0.23 at a phase angle of 3.2 degrees seems normal for a P-type asteroid. Long term integrations of the orbit shows that it is stable over time intervals of several million years.

Earth-bound observations of asteroid 19 Fortuna as support to HST imaging: lightcurves, pole direction and shape

Abstract To support the 19 Fortuna imaging work performed by the Hubble Space Telescope, this asteroid was photoelectrically observed in September 1993 at Mt. John, Lake Tekapo and Serra la Nave observatories, covering a complete rotational cycle. These observations and the unpublished ones, collected in November 1986 at Torino Observatory, allowed us to compute the value of the synodic rotational period, which results in accordance with that already known. The spin axis direction and the shape of 19 Fortuna were determined by applying the amplitude-magnitude method (Zappala et al. , in Asteroids, Comets, Meteors (edited by C.-I. Lagerkvist and H. Rickman), pp. 73–76. Uppsala Univeritet, Reprocentralen, HSC, Uppsala, 1983) to our data and to those reported in the literature. The values of the pole coordinates are in agreement with the previous determinations, while the ratio between the semi-axes a and b is larger than about 0.1.

LIGHTCURVES, POLE DIRECTION AND SHAPE OF ASTEROIDS 121 HERMIONE, 150 NUWA,236 HONORIA, 287 NEPHTHYS AND 377 CAMPANIA

Abstract Rotational periods, V lightcurves, B-V color indexes, rotation axis direction and shape of five asteroids are presented. The B and V photoelectric observations were carried out at Serra la Nave stellar station of Catania Astrophysical Observatory during March and August 1992 and May, July and September 1993. The synodic rotational periods determined are: 121 Hermione (P = 9h.238±0h.010), 150 Nuwa (P = 8h.140±0h.005), 236 Honoria (P = 12h.333±0h.006), 287 Nephthys (P = 7h.580±0h.004), 377 Campania (P = 8h.48±0h.01). No variation of the (B-V) color with the rotation appears for the asteroids observed. The determination of the pole direction and shape is performed by applying the Amplitude-Magnitude method (Zappala et al., Asteroids, Comets, Meteors, pp. 73–76. Uppsala Universitet, Reprocentralen, HSC, Uppsala, 1983) to the data collected by us and to those reported in the literature.

Mutual events between Jupiter's satellites observed in Catania during the PHEMU97 campaign

Abstract As a contribution to the PHEMU97 International Campaign, photoelectric observations of 80 phenomena between Jupiters satellites were made at M.G. Fracastoro station. After the reduction, 28 lightcurves were analysed to provide elements useful to determine accurate photometric position. In the framework of their publication in the PHEMU97 catalogue a preliminary study on the agreement between the predicted and observed characteristics of the lightcurves is presented.