(4528) Berg

V. Benishek, Belgrade Astronomical Observatory; P. Pravec, Ondrejov Observatory; G. Scarfi, Iota Scorpii Observatory, La Spezia, Italy; A. Coffano, W. Marinello, G. Pizzetti, and A. Soffiantini, Osservatorio Serafino Zani, Lumezzane, Italy; A. Marchini and R. Papini, Dipartimento di Scienze Fisiche, Della Terra e Dell'Ambiente, University of Siena; P. Bacci, M. Maestripieri, R. Bacci, and L. Franco, Astronomical Observatory, San Marcello Pistoiese, Italy; R. Durkee, Shed of Science South Observatory, Pontotoc, TX, U.S.A.; R. Goncalves, Linhaceira, Tomar, Portugal; N. Montigiani and M. Mannucci, Osservatorio Astronomico Margherita Hack, Firenze, Italy; G. Baj, M57 Observatory, Saltrio, Italy; and N. Ruocco, Osservatorio Astronomico Nastro Verde, Sorrento, Italy, report that photometric observations taken with a 0.35-m telescope at the Sopot Observatory in Serbia, a 0.40-m telescope at the Iota Scorpii Observatory, a 0.40-m telescope at the Lumezzane Observatory, a 0.30-m telescope at the Astronomical Observatory of the University of Siena, a 0.60-m telescope at the San Marcello Pistoiese Observatory, a 0.50-m telescope at the Shed of Science South Observatory, a 0.35-m telescope at the Linhaceira Observatory, a 0.25-m telescope at the Osservatorio Astronomico Margherita Hack, a 0.35-m telescope at the M57 Observatory, and a 0.35-m telescope at the Osservatorio Astronomico Nastro Verde during Feb. 2-May 7 reveal that minor planet (4528) is a binary system with an orbital period of 35.02 +/- 0.02 hr. The primary shows a period of 3.5627 +/- 0.0001 hr and has a lightcurve amplitude of 0.23 magnitude at solar phases 1-4 degrees. Mutual eclipse/occultation events that are 0.06 to 0.12 magnitude deep indicate a lower limit on the secondary-to-primary mean-diameter ratio of 0.3.