37th DPS Meeting, 4-9 September 2005
Session 14 Asteroid Discovery and Dynamics
Poster, Monday, September 5, 2005, 6:00-7:15pm, Music Foyer

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[14.07] The Orbit of 617 Patroclus Binary Trojan System from Keck LGS AO observations

F. Marchis (UC-Berkeley), D. Hestroffer, P. Descamps, J. Berthier (IMCCE), A. H. Bouchez (Caltech), R. D. Campbell, J. C. Y. Chin, M. A. van Dam, S. K. Hartman, E. M. Johansson, R. E. Lafon, D. Le Mignant (W.M. Keck Observatory), I. de Pater (UC-Berkeley), P.J. Stomski, D. M. Summers, P. L. Wizinovitch (W.M. Keck Observatory), M. H. Wong (UC-Berkeley)

We report the results from Laser Guide Star Adaptive Optics observations in 2004-2005 of 617 Patroclus using the NIRC2 camera at the W. M. Keck Observatory. An observing campaign which focuses on this only known binary Trojan asteroid, was initiated by our group. Both components of the system were detected at 5 different epochs between Nov. 2004 and May 2005 with an angular separation between 45 and 190 mas and a Dm ~0.17. The orbital parameters were estimated independently using two algorithms, a Monte-Carlo technique (Hestroffer and Vachier, IAU-ACM, 2005), and a visual binary method (Descamps, Cel. Mech., 2005): a= 685±40 km, e = 0.02±0.02, P = 4.287±0.002 or P= 2.391±0.003 corresponding to a total mass of 1.4 x 1018 or 4.3 x 1018 ±0.2 kg. Considering recent radiometric measurements by Fernandez et al., (AJ, 126, 2003), the radii of components would be R1= 60.9 km and R2=56.3 km (error~1.6 km and with \eta=0.94), leading to an averaged bulk density of 0.8 or 2.6 ±0.1 g/cm3. The factor of ~2 uncertainty in the period will be removed using additional observations from CADC archive (in progress).

In contrast to what was observed for a Kuiper-belt binary system (1998WW31 in Veillet et al., Nature, 2002), the low eccentricity is more common of main-belt binaries, indicating that dissipation effects must be considered.

This work was partly supported by the National Science Foundation Science and Technology Center for Adaptive Optics and a KPAC NASA grant.

If you would like more information about this abstract, please follow the link to http://astron.berkeley.edu/~fmarchis/Science/Asteroids. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: fmarchis@berkeley.edu

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.