Electronic Telegram No. 52
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
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1990 OS
     S. J. Ostro, Jet Propulsion Laboratory; M. C. Nolan, National Astronomy
and Ionosphere Center; L. A. M. Benner and J. D. Giorgini, Jet Propulsion
Laboratory; J. L. Margot, University of California, Los Angeles; and C.
Magri, University of Maine, Farmington, report that Arecibo radar delay-Doppler
images (2380 MHz, 12.6 cm) obtained on Nov. 5 and 6 show that 1990 OS (cf.
IAUC 5064; MPC 49636) is a binary system.  Preliminary estimates of average
diameters, based on range extents at 15-m resolution, are 300 and 45 m.  The
components' delay-Doppler dispersions suggest spin periods of several hours.
The maximum range separation observed is more than 600 m.  The pattern of
motion suggests an orbital period between 18 and 24 hr.  Optical lightcurve
observations of this object would be valuable.


NOTE: These 'Central Bureau Electronic Telegrams' are intended to
      be preliminary announcements of items that later appear in the
      formal IAU Circulars.  Citations should normally be made to IAUCs
      rather than to CBETs.

                         (C) Copyright 2003 CBAT
2003 November 8                   (CBET 52)               Daniel W. E. Green