Photometry of 2004 RZ164: a probable binary asteroid

¹ Astronomical Observatory, Adam Mickiewicz University, Słoneczna 36, 60-286 Poznań, Poland e-mail: tkastr@vesta.astro.amu.edu.pl
² Department of Physics, University of Rome Tor Vergata, via della Ricerca Scientifica 1, 00133 Rome, Italy
³ Modra Observatory, Department of Astronomy, Physics of the Earth, and Meteorology, FMPI, Comenius University, 842 48 Bratislava, Slovakia
⁴ Astronomical Institute AS CR, 251 65 Ondřejov, Czech Republic
⁵ Instituto Politecnico de Tomar, Area de Fisica, 2300-313 Tomar, Portugal
⁶ Institut de Mécanique Céleste, 77 Av. Denfert Rochereau, 75014 Paris, France

Received: 18 April 2006
Accepted: 27 September 2006

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 , 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 and the orbital period of the system is longer than .