UBV photometry of the minor planets 86 Semele, 521 Brixia, 53 Kalypso and 113 Amalthea

The asteroids were observed photometrically during the 1980 and 1981 oppositions, respectively. The V lightcurve of 86 Semele displays two asymmetric maxima and minima with a total amplitude DeltaV = 0.18 mag. Its synodic rotation period is P[SUB]s[/SUB] = 16h38m02" ± 16" and the color indices B-V = 0.690 ± 0.011 and U-B = 0.320 ± 0.015 mag. 521 Brixia is a slow rotator (P[SUB]s[/SUB] > 24h) showing light variations greater than DeltaV â 0.09 mag and with color indices B-V = 0.714 ± 0.008 and U-B = 0.337 ± 0.011 mag. 53 Kalypso rotates with a period P[SUB]s[/SUB] = 26h33m ± 4m with a total light amplitude DeltaV > 0.10 mag and color indices B-V = 0.692 ± 0.015 and U-B = 0.341 ± 0.022 mag. The lightcurve of 113 Amalthea shows large amplitude variations (DeltaV > 0.26 mag) with a broad minimum and the rotation period is greater than 12h with color indices B-V = 0.888 ± 0.012 and U-B = 0.487 ± 0.019 mag.