Photometric Studies of Asteroids.IV. The Light-Curves of Ceres, Hebe, Flora, and Kalliope.

The variation of the magnitudes of four asteroids-Ceres, Hebe, Flora, and Kalliope-has been investigated with the photoelectric photometers on the 82-inch reflector at the McDonald Observatory and on the I24nch refractor of the Yerkes Observatory. The magnitude of Flora was nearly constant at the epoch of observation; for the other three asteroids the light varied, and the period of variation was determined. Ceres showed a range of 0.04 mag., with a period of 9 7; Hebe a range of 0.16 mag. and a period of Kalliope a range of 0.14 mag. and a period of 8. The latter is the shortest period that has been definitely established for an asteroid. All three asteroids show two maxima and minima. Hebe is the only asteroid observed by us over a long enough interval to establish the phase factor; the value is 0.04S mag$degree.