Electronic Telegram No. 4063
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


(357439) 2004 BL_86
      J. Pollock, Appalachian State University; P. Pravec, Ondrejov
Observatory; J. Oey, Blue Mountains Observatory, Leura, NSW; and D. E.
Reichart, J. B. Haislip and A. P. LaCluyze, University of North Carolina,
Chapel Hill, report that photometric observations obtained during 2015
Jan. 20-24 reveal that minor planet (357439) is a binary system with
an orbital period of 13.80 +/- 0.05 hr.  The primary shows a period of
2.6205 +/- 0.0003 hr, and it has a lightcurve amplitude of 0.17 mag at
solar phases 99-109 deg, suggesting a nearly spheroidal shape. Mutual
eclipse/occultation events that are 0.05- to 0.07-magnitude deep
indicate a secondary-to-primary mean-diameter ratio of 0.21 +/- 0.02.
     Minor planet 2004 BL_86 was discovered eleven years ago by the LINEAR
program (cf. MPEC 2004-B80) and was later numbered (357439).

     Lance A. M. Benner, on behalf of the radar team reports that Goldstone
delay-Doppler radar (8560-MHz, 3.5-cm, 3.75-m resolution) images obtained on
2015 Jan. 26 confirm that (357439) is a binary system.  Preliminary
estimates for diameters of the components are 300 m for the primary and
50-100 m for the secondary.
     Forty-four minor planets passing close to the earth have now been found
to have companions via radar (eight of those discovered first via optical
photometry), and at least two such minor planets have more than one companion.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2015 CBAT
2015 January 30                  (CBET 4063)              Daniel W. E. Green