Electronic Telegram No. 4139
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
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e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
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Prepared using the Tamkin Foundation Computer Network


(348400) 2005 JF_21
     S. P. Naidu, L. A. M. Benner, M. Brozovic, J. D. Giorgini, J. S. Jao,
C. G. Lee, L. G. Snedeker, and K. J. Lawrence, Jet Propulsion Laboratory,
California Institute of Technology; and M. W. Busch, SETI Institute, report
that Goldstone radar (8560 MHz, 3.5 cm) delay-Doppler images and echo power
spectra obtained on Aug. 10 reveal that the near-earth minor planet (348400)
2005 JF_21 is a binary system.  In the images with range resolutions of 150 m,
the range extent of the primary is 0.3 km.  The secondary is unresolved in
range.  The two components are separated by about 5.4 km in range, and there
is no obvious change in the separation over about 2 hours.  The echo power
spectra show a second narrow spike that persists at similar frequencies
throughout observations lasting about 2.5 hours.  This spike is at a
frequency distinct from that of the satellite visible in the images and is
consistent with the presence of another satellite.  The images appear to show
a faint feature overlapping the primary in range at the same frequency as
the narrow spike but are too weak to confirm the presence of a second
satellite.  Lightcurve observations could reveal mutual events and are
highly desirable to understand this system.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2015 CBAT
2015 August 22                   (CBET 4139)              Daniel W. E. Green