Electronic Telegram No. 5667
Central Bureau for Astronomical Telegrams
Mailing address:  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


(6311) PORUBCAN
     R. Durkee, Shed of Science South Observatory, Pontotoc, TX, U.S.A.; P.
Pravec, Ondrejov Observatory; N. Ruocco, Osservatorio Astronomico Nastro
Verde, Sorrento, Italy; M. Husarik and G. Cervak, Skalnate Pleso Observatory;
D. Pray, Sugarloaf Mountain Observatory, South Deerfield, MA, U.S.A.; and P.
Bacci and M. Maestripieri, Astronomical Observatory, San Marcello Pistoiese,
Italy, report that photometric observations taken with a 0.50-m telescope at
the Shed of Science South Observatory, a 0.35-m telescope at the Osservatorio
Astronomico Nastro Verde, 0.61-m and 1.3-m telescopes at the Skalnate Pleso
Observatory, a 0.63-m telescope at the Sugarloaf Mountain Observatory, and a
0.60-m telescope at the San Marcello Pistoiese Observatory during 2025 Dec.
10-2026 Feb. 10 reveal that minor planet (6311) is a binary system with an
orbital period of 21.11 +/- 0.01 hr.  The primary shows a period of 4.0960 +/-
0.0002 hr and has a lightcurve amplitude of 0.08 magnitude at solar phases
7-20 degrees, suggesting a nearly spheroidal shape.  Mutual eclipse/
occultation events that are 0.06 magnitude deep indicate a lower limit on the
secondary-to-primary mean-diameter ratio of 0.24.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2026 CBAT
2026 February 24                 (CBET 5667)              Daniel W. E. Green