(8306) Shoko
Abstract
P. Pravec, P. Kusnirak, K. Hornoch, and A. Galad, Ondrejov Observatory and European Southern Observatory, La Silla; Yu. N. Krugly and V. Chiorny, Kharkiv Observatory; R. Inasaridze, O. Kvaratskhelia, and V. Ayvazian, Abastumani Observatory; O. Parmonov, Maidanak Observatory; J. Pollock, Appalachian State University; S. Mottola, Calar Alto Observatory; J. Oey, Blue Mountains Observatory, Leura, NSW; D. Pray, Sugarloaf Mountain Observatory, South Deerfield, MA, U.S.A.; J. Zizka and J. Vrastil, Charles University, Prague; I. Molotov, Keldish Institute of Applied Mathematics, Moscow; and D. E. Reichart, K. M. Ivarsen, J. B. Haislip, and A. LaCluyze, Physics and Astronomy Department, University of North Carolina at Chapel Hill, report that photometric observations obtained during 2013 Sept. 7-Dec. 7 reveal that minor planet (8306) is a binary system with an orbital period of 36.20 +/- 0.04 hr. The primary shows a period of 3.3503 +/- 0.0002 hr, and it has a lightcurve amplitude of 0.11 mag at solar phases 3-13 deg, suggesting a nearly spheroidal shape. Mutual eclipse/occultation events that are up to 0.26 mag deep indicate a lower limit on the secondary-to-primary mean-diameter ratio of 0.40. The secondary shows a period equal to the orbital period, indicating synchronous rotation. Residuals of the fit show an additional brightness variation that may be due to rotation of a third body of the system. The mean absolute R magnitude of the system is H_R = 14.83 +/- 0.07, assuming G = 0.24 +/- 0.11. 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 (8306) was selected as a target when found that it appears paired with minor planet 2011 SR_158 using the method of Pravec and Vokrouhlicky (2009, Icarus 204, 580), modified with use of the mean elements from AstDyS-2 (see website URL http://hamilton.dm.unipi.it/astdys2/) and with backward integrations of their orbits using the method of Vokrouhlicky (2009, Ap.J. 706, L37). The integrations indicate that the pair separated from a single body between 300 and 650 kyr ago.
- Publication:
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International Astronomical Union Circular
- Pub Date:
- December 2013
- Bibcode:
- 2013IAUC.9268....1P