Electronic Telegram No. 5626
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
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Prepared using the Tamkin Foundation Computer Network


(458122) 2010 EW_45
     L. A. M. Benner, M. Brozovic, S. P. Naidu, and J. D. Giorgini, Jet
Propulsion Laboratory, California Institute of Technology; and M. W. Busch,
SETI Institute, report that Goldstone (8560 MHz, 3.5 cm) radar observations
obtained during 2024 Dec. 17-23 reveal that minor planet (458122) is a binary
system.  Delay-Doppler images at 150-meter resolution show two objects whose
positions change in time delay and Doppler frequency with a maximum separation
of at least 600 meters.   A preliminary estimate for the diameter of the
primary is about 450-600 meters.  The secondary was not resolved.  Goldstone
observations place an upper bound on the orbital period of < 16 hours and
suggest that the primary's rotation period is less than three hours.
      P. Pravec, K. Hornoch, P. Kusnirak, P. Fatka, and H. Kucakova, Ondrejov
Observatory, report that photometric observations taken with a 1.54-m
telescope at the La Silla station of the European Southern Observatory during
2025 Jan. 2-8 reveal that the Apollo-type minor planet (458122) is a binary
system with an orbital period of 12.71 +/- 0.04 hr.  The primary has a period
of 2.4889 +/- 0.0006 hr and a lightcurve amplitude of 0.09 magnitude at solar
phases 24-26 degrees, suggesting a nearly spheroidal shape.  Mutual eclipse/
occultation events that are 0.12 magnitude deep indicate a secondary-to-
primary mean-diameter ratio of 0.34 +/- 0.02.  The secondary appears
synchronous and has a light-curve amplitude (in the combined primary-plus-
secondary light curve) of 0.05 mag, suggesting a moderately elongated shape
with an equatorial-axis ratio of 1.35 +/- 0.12.  The system's mean absolute
magnitude is H = 17.72 +/- 0.29, assuming a phase-relation slope parameter G
= 0.20 +/- 0.20.  The color index in the Johnson-Cousins photometric system is
(V - R) = +0.427 +/- 0.010.  These observations were taken in the framework of
their NEOSource project, supported by the "Praemium Academiae" award from the
Academy of Sciences of the Czech Republic.


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                         (C) Copyright 2025 CBAT
2025 October 27                  (CBET 5626)              Daniel W. E. Green