Electronic Telegram No. 1339 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT@CFA.HARVARD.EDU (science) URL http://www.cfa.harvard.edu/iau/cbat.html (5481) KIUCHI P. Kusnirak and P. Pravec, Ondrejov Observatory; J. Oey, Leura, N.S.W., Australia; R. Stephens, Goat Mountain Astronomical Research Station, Yucca Valley, CA, U.S.A.; M. Husarik, Skalnate Pleso Observatory; and J. Ries, McDonald Observatory, report that photometric observations obtained during Mar. 13 to Apr. 6 reveal that minor planet (5481) is a binary system with an orbital period of 20.90 +/- 0.01 hr. The primary shows a period of 3.6196 +/- 0.0002 hr, and it has a lightcurve amplitude of 0.10 mag, suggesting a nearly spheroidal shape. Mutual eclipse/occultation events indicate a secondary-to-primary mean-diameter ratio of 0.33 +/- 0.02. The mean absolute R magnitude is H = 12.98 +/- 0.1, assuming G = 0.15 +/- 0.2. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2008 CBAT 2008 April 15 (CBET 1339) Daniel W. E. Green