Photometry of 2004 RZ164: A probable binary asteroid

Abstract

Aims. 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 0m.15, 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 h.5559 ± 0h.0001 and the orbital period of the system is longer than 10h.8. © ESO 2007.