Binary asteroid discovery IAU announcement


V. Benishek, Belgrade Astronomical Observatory; P. Pravec, H. Kucakova,
and K. Hornoch, Ondrejov Observatory; V. Chiorny, Kharkiv Observatory; F.
Pilcher, Organ Mesa Observatory, Las Cruces, NM, U.S.A.; A. Aznar, Astronomia
Para Todos Observatories Group, Spain; and V. Casanova, Observatorio de Sierra
Nevada, Instituto de Astrofisica de Andalucia, Consejo Superior de
Investigaciones Cientificas, report that photometric observations taken with a
0.35-m telescope at the Sopot Observatory in Serbia, a 0.65-m telescope at the
Ondrejov Observatory, a 0.70-m telescope at the Chuguev station of the Kharkiv
Observatory in Ukraine, a 0.35-m telescope at the Organ Mesa Observatory, and
a 0.90-m telescope at Sierra Nevada Observatory during Sept. 18-Oct. 15 reveal
that minor planet (2178) is a binary system with an orbital period of 18.504
± 0.006 hr. The primary shows a period of 3.0183 ± 0.0002 hr and has a
light-curve amplitude of 0.31 mag at solar phases 8-11 degrees. Mutual
eclipse/occultation events that are 0.07 to 0.15 magnitude deep indicate a
secondary-to-primary mean-diameter ratio of 0.26 ± 0.02. The secondary
appears synchronous and has a light-curve amplitude (in the combined primary
plus secondary light curve) of 0.02 mag, suggesting a moderately elongated
shape with the equatorial axis ratio of 1.3 ± 0.1.