EDP Sciences
Free access
Volume 483, Number 2, May IV 2008
Page(s) L17 - L20
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200809474
Published online 08 April 2008

A&A 483, L17-L20 (2008)
DOI: 10.1051/0004-6361:200809474


Physical and dynamical properties of (12929) 1999 TZ1 suggest that it is a Trojan

A. Moullet1, E. Lellouch1, A. Doressoundiram1, J. L. Ortiz2, R. Duffard2, A. Morbidelli3, P. Vernazza1, and R. Moreno1

1  LESIA-Observatoire de Paris, 5 place J. Janssen, 92195 Meudon, France
    e-mail: arielle.moullet@obspm.fr
2  CSIC-Instituto de Astrofisíca de Andalusía, Granada, Spain
3  Observatoire de la Côte d'Azur, Nice, France

(Received 28 January 2008 / Accepted 27 March 2008)

Context. Small body (12929) 1999 TZ1 is listed by the Minor Planet Center (MPC) as a Centaur. However, its location close to the Lagrangian point L5 of Jupiter is typical of a Trojan object with large inclination.
Aims. The aim of this work is to provide a global physical and dynamical characterization of this object and to reassess its classification.
Methods. We obtained multi-wavelength observations with IRTF (Hawaii), OSN and IRAM-30 m (Spain), and performed a dynamical simulation of the evolution of its orbital parameters.
Results. Visible photometry monitoring shows a rotation curve with a period (if considered double-peaked) of 10.4 $\pm$ 0.1 h and an absolute R magnitude HR = 9.792 $\pm$ 0.025. Near-IR spectroscopy indicates a featureless reflectance spectra, with a low spectral slope of 7.2 $\pm$ 0.11%/100 nm. Thermal observations at 250 GHz provide a 4.5$\sigma$ detection with a flux of 1.22 $\pm$ 0.27 mJy. The combination of the visible and millimeter datasets, assuming a standard thermal model, leads to a geometric albedo pv = $0.053^{{\rm +0.015}}_{{-0.010}}$ and a mean diameter of 51.5 $\pm$ 5 km.
Conclusions. The low albedo and spectral slope measured are typical of Jupiter's Trojans, but cannot exclude a Centaur nature. However, the dynamical lifetime of the object was estimated to be longer than 1 Gy, which is unlikely for a Centaur and suggests that (12929) 1999 TZ1 is a Trojan asteroid.

Key words: minor planets, asteroids -- radio continuum: solar system -- infrared: solar system -- celestial mechanics

© ESO 2008