Photometry and models of selected main belt asteroids. VII. 350 Ornamenta, 771 Libera, and 984 Gretia

International audience; We analyze photometric observations of the three main-belt asteroids 350 Ornamenta, 771 Libera, and 984 Gretia, conducted over a twelve-year interval. Our data and those of other authors allow us to determine pole and shape models using the lightcurve inversion technique. In all three cases, a single pole solution was obtained without any significant mirror solution: Ornamenta - P = 9.180 414 h, lambdap = 184°, betap = -29° Libera - P = 5.890 423 h, lambdap = 64°, betap = -78° Gretia - P = 5.778 025 h, lambdap = 245°, betap = +52°. This analysis and the development of asteroid models increase the set of asteroids with known spin and shape parameters, which consists of only around 100 objects.