Electronic Telegram No. 4347
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
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(163693) ATIRA
     E. G. Rivera-Valentin, P. A. Taylor, A. Virkki, and B. Aponte-Hernandez,
Arecibo Observatory, Universities Space Research Association, report that
Arecibo (2380 MHz, 12.6 cm) delay-Doppler radar images obtained on 2017 Jan.
20 and 23 reveal that the near-earth minor planet (163693) is a binary system.
Visible range extents of the components in images with a resolution of 150
m/pixel suggest a primary up to 4.8 +/- 0.5 km in diameter and a secondary
1.0 +/- 0.3 km in diameter.  The primary is possibly elongated and very
angular in shape.  On Jan. 20, the system was observed near maximum
separation in delay (range), suggesting a mutual-orbit scale of at least 5.7
km.  On Jan. 23, the system was observed near maximum separation in Doppler
frequency, suggesting an orbital period of roughly 16 hours.  A preliminary
circular orbit fit finds a (projected) semimajor axis of 6 km and a period
of 15.5 hours.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2017 CBAT
2017 January 28                  (CBET 4347)              Daniel W. E. Green