Electronic Telegram No. 5039
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
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(326732) 2003 HB_6
     P. Pravec, K. Hornoch, H. Kucakova, P. Kusnirak, and P. Fatka, Ondrejov
Observatory; E. Jehin and M. Ferrais, Liege University; M. Devogele, Arecibo
Observatory and University of Central Florida; T. Kareta, University of
Arizona; and N. Moskovitz, Lowell Observatory, report that photometric
observations taken with a 0.65-m telescope at Ondrejov Observatory and a
0.6-m telescope at the La Silla station of the European Southern Observatory
during Aug. 10-Sept. 15 reveal that the Amor-type minor planet (326732) is a
binary system with an orbital period of 22.92 +/- 0.05 hr.  The primary has a
period of 3.4630 +/- 0.0008 hr and a lightcurve amplitude of 0.08 magnitude at
solar phases 4-8 degrees, suggesting a nearly spheroidal shape.  Mutual
eclipse/occultation events that are 0.06 to 0.11 magnitude deep indicate a
secondary-to-primary mean-diameter ratio of 0.23 +/- 0.02.  The secondary
appears synchronous and has a light-curve amplitude (in the combined primary-
plus-secondary light curve) of 0.02 mag, suggesting a moderately elongated
shape with an equatorial-axis ratio of 1.4 +/- 0.2.  The system's mean
absolute magnitude is H = 17.42 +/- 0.04, assuming a phase-relation slope
parameter G = 0.24 +/- 0.11.  The color index in the Johnson-Cousins
photometric system is (V - R) = 0.429 +/- 0.010.  Spectroscopic observations
taken with the DeVeny spectrograph at the 4.3-m Lowell Discovery Telescope in
the wavelength range 0.38-1.0 micron suggest it to be of L-type in the
Bus-DeMeo taxonomic system, but other classifications are not excluded.  These
observations were taken in the framework of their NEOROCKS and MANOS projects.
Follow-up observations are encouraged.


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2021 September 18                (CBET 5039)              Daniel W. E. Green