Photometry of 2004 RZ164: a probable binary asteroid

International audienceAims:We observed a near-Earth asteroid 2004 RZ164 to study its rotational properties. The object was chosen because of its small diameter of about 700 m, which is close to the 150 m threshold, separating monolithic and rubble-pile asteroids. Methods: With small telescopes at five observatories, equipped with CCD cameras, we obtained seven lightcurves, which were taken through the clear, R, and I filters. Results: Despite significant changes in the observing geometries (and large phase angles during observations), the peak-to-peak amplitudes of the lightcurves never exceeded 0.15 m, suggesting the almost spheroidal shape of this asteroid. There is a signature of a probable occultation/eclipse event in one of the lightcurves, which suggests 2004 RZ164 is a binary asteroid. Its primary component spins with a period of P=2.5559 h ± 0.0001 h and the orbital period of the system is longer than 10.8 h