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Radar and photometric observations and shape modeling of contact binary near-Earth Asteroid (8567) 1996 HW1 |
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| Authors: | Christopher Magri Ellen S Howell Patrick A Taylor Michael Mueller Lance AM Benner Steven J Ostro Michael D Hicks James M Somers Vladimir V Kouprianov Igor E Molotov Jean-Luc Margot Vojislava Protitch-Benishek David Higgins Donald P Pray |
| Institution: | a University of Maine at Farmington, 173 High Street - Preble Hall, Farmington, ME 04938, USA b Arecibo Observatory, HC3 Box 53995, Arecibo, PR 00612, USA c University of Central Florida, Dept. of Physics, 4000 Central Florida Blvd., Orlando, FL 32828, USA d Université de Nice Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, BP 4229, 06304 Nice Cedex 4, France e JHU/Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099, USA f Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA g Department of Aerospace Engineering Sciences, University of Colorado at Boulder, 429 UCB, Boulder, CO 80309-0429, USA h Moorpark College, 7075 Campus Rd, Moorpark, CA 93021, USA i Crimean Astrophysical Observatory, Simeiz Department, Crimea 98680, Ukraine j Pulkovo Observatory of the Russian Academy of Sciences, Pulkovskoje Ave. 65-1, 196140 St. Petersburg, Russia k Institute of Astronomy of Kharkiv National University, Sumska Str. 35, Kharkiv 61022, Ukraine l Keldysh Institute of Applied Mathematics, RAS, Miusskaya Sq. 4, Moscow 125047, Russia m Department of Earth and Space Sciences, University of California, Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095, USA n Belgrade Astronomical Observatory, Volgina 7, 11060 Belgrade 38, Serbia o Modra Observatory, Department of Astronomy, Physics of the Earth, and Meteorology, FMFI UK, Bratislava SK-84248, Slovakia p Astronomical Institute, Academy of Sciences of the Czech Republic, Fri?ova 1, CZ-25165 Ond?ejov, Czech Republic q Hunters Hill Observatory, 7 Malawan Street, Canberra, Australia r Carbuncle Hill Observatory, P.O. Box 946, Coventry, RI 02816, USA |
| Abstract: | We observed near-Earth Asteroid (8567) 1996 HW1 at the Arecibo Observatory on six dates in September 2008, obtaining radar images and spectra. By combining these data with an extensive set of new lightcurves taken during 2008-2009 and with previously published lightcurves from 2005, we were able to reconstruct the object’s shape and spin state. 1996 HW1 is an elongated, bifurcated object with maximum diameters of 3.8 × 1.6 × 1.5 km and a contact-binary shape. It is the most bifurcated near-Earth asteroid yet studied and one of the most elongated as well. The sidereal rotation period is 8.76243 ± 0.00004 h and the pole direction is within 5° of ecliptic longitude and latitude (281°, −31°). Radar astrometry has reduced the orbital element uncertainties by 27% relative to the a priori orbit solution that was based on a half-century of optical data. Simple dynamical arguments are used to demonstrate that this asteroid could have originated as a binary system that tidally decayed and merged. |
| Keywords: | Asteroids Photometry Radar observations |
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