Electronic Telegram No. 4088
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


(26416) 1999 XM84
      P. Pravec, P. Kusnirak, K. Hornoch, and A. Galad, Ondrejov Observatory
and European Southern Observatory, La Silla; and J. Zizka, Charles University,
Prague, report that photometric observations obtained during Mar. 16-29
confirm the suggestion by Polishook (2014, Minor Planet Bull. 41, 49) that
minor planet (26416) is a binary system.  It has an orbital period of 20.76
+/- 0.01 hr.  The primary shows a period of 2.9660 +/- 0.0001 hr, and it has
a lightcurve amplitude of 0.10 mag at solar phases 9-15 deg, suggesting a
nearly spheroidal shape.  Mutual eclipse/occultation events that are 0.08 mag
deep indicate a lower limit on the secondary-to-primary mean-diameter ratio
of 0.27.  The mean absolute magnitude of the system is H = 14.57 +/- 0.05,
and the phase slope parameter is G = 0.19 +/- 0.05.  These observations were
run as a part of their photometric project "NEOSource" within its task to
study binary and multiple systems among minor-planet pairs [i.e., pairs of
minor planets that are in highly similar heliocentric orbits (see Vokrouhlicky
and Nesvorny 2008, A.J. 136, 280; Pravec et al. 2010, Nature 466, 1085)].
Minor planet (26416) was selected as a target, as it was found to appear
paired with minor planet (214954) 2007 WO58 (Pravec and Vokrouhlicky 2009,
Icarus 204, 580).  Backward integrations of their orbits indicate that the
pair components separated between 190 and 530 kyr ago.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2015 CBAT
2015 April 2                     (CBET 4088)              Daniel W. E. Green