Electronic Telegram No. 4191
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)
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Prepared using the Tamkin Foundation Computer Network


(410777) 2009 FD
     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; M. W. Busch, SETI Institute; and P. A.
Taylor, J. E. Richardson, and E. G. Rivera-Valentin, Arecibo Observatory,
report that Goldstone (X-band, 8560-MHz, 3.5-cm) and Arecibo (S-Band,
2380-MHz, 12.6-cm) delay-Doppler radar images and echo power spectra obtained
between Oct. 25 and Nov. 4 reveal that the near-Earth minor planet (410777)
is a binary system.  In images with range resolutions of 7.5 m, the range
extents of the primary and secondary are about 60-90 m and about 30-60 m,
respectively.  For spherical objects, the visible extents are roughly their
radii, hence the diameters of the two components are roughly 120-180 m and
60-120 m.  The maximum range separation between the two components is about
250 m.  The circular polarization ratio (SC/OC) at S-band is roughly 0.18 +/-
0.05.  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      superseded by text appearing later in the printed IAU Circulars.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 November 19                 (CBET 4191)              Daniel W. E. Green