Title
Photometric observations and modeling of asteroid 1620 Geographos
Date Issued
01 January 1996
Access level
metadata only access
Resource Type
journal article
Author(s)
Magnusson P.
Dahlgren M.
Barucci M.A.
Jorda L.
Binzel R.P.
Slivan S.M.
Blanco C.
Riccioli D.
Buratti B.J.
Berthier J.
De Angelis G.
Di Martino M.
Dotto E.
Drummond J.D.
Fink U.
Hicks M.
Grundy W.
Wisniewski W.
Gaftonyuk N.M.
Geyer E.H.
Bauer T.
Hoffmann M.
Ivanova V.
Komitov B.
Donchev Z.
Denchev P.
Krugly Y.N.
Velichko F.P.
Chiorny V.G.
Lupishko D.F.
Shevchenko V.G.
Kwiatkowski T.
Kryszczynska A.
Lahulla J.F.
Licandro J.
Mendez O.
Mottola S.
Erikson A.
Ostro S.J.
Pravec P.
Pych W.
Tholen D.J.
Whiteley R.
Wild W.J.
Wolf M.
Šarounovà L.
Bureau des Longitudes
Publisher(s)
Academic Press Inc.
Abstract
Photometric observations of 1620 Geographos in 1993 and 1994 are presented and, in combination with previously published data, are used to derive models of Geographos. We estimate that the sidereal period of rotation is 0.21763860 ± 0.00000003 days (5h13m23.975s ± 0.003s). The sense of rotation is retrograde. The ecliptic coordinates of the spin angular velocity vector are estimated to λp = 56° ± 6° and βp = -47° ± 4° (equinox J2000.0). The lightcurve amplitudes are well-explained by an ellipsoidal model with axis ratios a/b = 2.58 ± 0.16 and b/c = 1.00 ± 0.15. Models that have one or both ends more sharply pointed than the ellipsoid improve the fit to the observations. There are no significant indications of albedo variegation, but non-geometric scattering effects are tentatively suggested based on significant rotational color variation. © 1996 Academic Press, Inc.
Start page
227
End page
244
Volume
123
Issue
1
Language
English
OCDE Knowledge area
AstronomÃa
Scopus EID
2-s2.0-16144366535
Source
Icarus
ISSN of the container
00191035
Source funding
National Aeronautics and Space Administration
Sponsor(s)
Detailed reviews by Drs. B. Zellner and D. Simonelli improved the manuscript in many ways. We are grateful to P. Kubìcˇek and M. Varady for assistance during observations at Ondrejov Observatory and to E. Roettger and J. Mosher (JPL) for help with observations and reductions. De Angelis is personally indebted to Jose Alonso, Gaetano Andreoni, Emilio Barrios, Edgardo Figueroa Giovannetti, Augusto Macchino, Jose Mendez, Angel Otarola, Enrique Schmidt, Arturo Torrejon, and Saul Vidal, and grateful to all the ESO La Silla Staff for the nice, continuous, and generous support given during his observation run. Ivanova and Komitov are grateful to Dr. Jockers from Max-Planck Institute for Aeronomy for the opportunity to use their focal reducer and CCD camera in November and December 1993 and to Dr. N. Kiselev for his help in the December 1993 observations. The observations were supported by the Bulgarian National Scientific Foundation grant under Contract F-90/1991 with the Bulgarian Ministry of Education and Science. The Kharkiv group thanks R. A. Mohamed for help during the two observation runs in September 1995. The Kharkiv team was partially supported by the Russian Fund of Fundamental Exploration and the ISF Grant U9F 000. Krugly acknowledges the support from the American Astronomical Society. Magnusson was supported by the Swedish National Space Board (‘‘Rymdstyrelsen’’) and by the Swedish Natural Science Research Council (‘‘NFR’’). Kwiatkowski and Pych were supported by the Polish Grant KBN 2 P304 017 06. Fink was supported by a Humboldt fellowship. Fink, Grundy, and Hicks were supported by NASA Grant NAGW 1549. Pravec and Wolf were supported in part by a grant within the ESO C&EE Programme No. A-02-069. Part of this research was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). Part of the data were taken at the 61’’ Catalina Site telescope of the University of Arizona Observatories with the CCD system of Dr. Uwe Fink. We thank the German–Spanish Astronomical Center, operated by the Max-Planck Institut für Astronomie (Heidelberg) jointly with the Spanish National Commission for Astronomy. The Uruguayan group was partly supported from Proyecto CONICYT-BID #45, Area FÃsica. The Jacobus Kepteyn Telescope is operated on the island of La Palma by the Royal Greenwich Observatory in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de AstrofÃsica de Canarias. T. MichaÅ‚owski offered valuable advice on the manuscript.
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