Electronic Telegram No. 2698 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; 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 (3951) ZICHICHI P. Antonini, Bedoin, France; R. Behrend, Geneva Observatory; F. Colas and J. Lecacheux, Paris Observatory; R. Goncalves, Linhaceira, Portugal; D. Starkey, Auburn, IN, U.S.A.; F. Manzini, Sozzago, Italy; V. Reddy, University of North Dakota; H. and H. Hamanowa, Motomiya, Fukushima, Japan; and R. Naves, Barcelona, Spain, report that photometric observations obtained during 2006 Nov. 29 to 2007 Feb. 11 revealed that minor planet (3951) had a rotation lightcurve with a period of 3.3944 hr and amplitude of 0.32 mag, to which there were superimposed attenuations with depths of about 0.1 mag resembling mutual events in a binary system -- but a unique solution for their period was not obtained, so the binary nature of the asteroid was not unambiguously established. M. Husarik, Z. Kanuchova, Z. Krisandova, and M. Pikler, Skalnate Pleso Observatory; P. Pravec and P. Kusnirak, Ondrejov Observatory; J. Pollock, Appalachian State University; R. Durkee, Shed of Science Observatory, Minneapolis, MN, U.S.A.; J. Vilagi, S. Gajdos, A. Galad, and P. Veres, Modra Observatory; and D. E. Reichart, K. M. Ivarsen, J. B. Haislip, and A. LaCluyze, Physics and Astronomy Department, University of North Carolina at Chapel Hill, report that photometric observations obtained during 2011 Jan. 26 to Apr. 3 confirmed that minor planet (3951) is a binary system and estimated an orbital period of 27.59 +/- 0.01 hr. The primary shows a period of 3.39423 +/- 0.00007 hr, and it has a lightcurve amplitude of 0.26 mag. Mutual eclipse/occultation events that are 0.12- and 0.23-mag deep indicate a lower limit on the secondary-to-primary mean-diameter ratio of 0.33. F. Marchis, J. E. Enriquez, and M. Allain, Carl Sagan Center at the SETI Institute; and J. P. Emery, University of Tennessee at Knoxville, report on integrated spectroscopic observations of the binary system (3951) recorded from 2011 Apr. 1.276 to 1.353 UT with Infrared Telescope Facility's SPEX instrument. A solar analogue (SAO 97748) was observed before and after the target to compute a final reflectance spectrum from 0.67 to 2.55 microns. Following the Bus-DeMeo taxonomy, the near-infrared spectrum is typical of S-type minor planets, characterized by moderate 1- and 2-micron absorption band features. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2011 CBAT 2011 April 14 (CBET 2698) Daniel W. E. Green