Electronic Telegram No. 5412
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
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2021 CJ_16
     P. Pravec, P. Kusnirak, K. Hornoch, H. Kucakova, and P. Fatka, Ondrejov
Observatory, report that photometric observations taken with a 1.54-m
telescope at the La Silla station of the European Southern Observatory during
2024 Apr. 9-May 12 reveal that the Amor-type minor planet 2021 CJ_16 is a
binary system with an orbital period of 16.28 +/- 0.02 hr.  Mutual eclipse/
occultation events that are 0.56 to 0.70 magnitude deep indicate a lower limit
on the secondary-to-primary mean-diameter ratio of 0.82.  There is apparent a
rotational lightcurve at orbital phases outside the mutual events with a
period equal to the orbital period and an amplitude of 0.22 magnitude at solar
phases 7-35 degrees, suggesting that one or both components of the binary
system are synchronous and moderately elongated.  The system's mean absolute
magnitude is H = 20.20 +/- 0.04 with a phase-relation slope parameter G = 0.29
+/- 0.03.  The color index in the Johnson-Cousins photometric system is
(V - R) = +0.41 +/- 0.02.  Follow-up observations (e.g., photometric or
spectroscopic) taken during the rest of the current observable apparition of
the minor planet are encouraged so as to improve the characterization of the
binary system.


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                         (C) Copyright 2024 CBAT
2024 July 10                     (CBET 5412)              Daniel W. E. Green