Electronic Telegram No. 5189 Central Bureau for Astronomical Telegrams Mailing address: Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network (4901) O BRIAIN V. Benishek, Belgrade Astronomical Observatory; P. Pravec, Ondrejov Observatory; B. Warner, Center for Solar System Studies, Lander, CA, USA; and J. Oey, Blue Mountains Observatory, Leura, NSW, Australia, report that photometric observations taken with a 0.35-m telescope at the Sopot Observatory in Serbia, a 0.30-m telescope at the Center for Solar System Studies, and a 0.35-m telescope at the Blue Mountains Observatory during July 14-Sept. 19 reveal that minor planet (4901) is a binary system with an orbital period of 47.6 +/- 0.1 hr. The primary shows a period of 2.6498 +/- 0.0001 hr and has a lightcurve amplitude of 0.11 mag at solar phases 5-10 degrees, suggesting a nearly spheroidal shape. Mutual eclipse/occultation events that are 0.08 magnitude deep indicate a lower limit on the secondary-to-primary mean-diameter ratio of 0.28. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2022 CBAT 2022 November 7 (CBET 5189) Daniel W. E. Green