2008A&A...483L..17M

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. The aim of this work is to provide a global physical and dynamical characterization of this object and to reassess its classification. 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. Visible photometry monitoring shows a rotation curve with a period (if considered double-peaked) of 10.4±0.1h and an absolute R magnitude H_R=9.792±0.025. Near-IR spectroscopy indicates a featureless reflectance spectra, with a low spectral slope of 7.2±0.11%/100nm. Thermal observations at 250GHz provide a 4.5σ detection with a flux of 1.22±0.27mJy. The combination of the visible and millimeter datasets, assuming a standard thermal model, leads to a geometric albedo p_v=0.053^+0.015_–0.010 and a mean diameter of 51.5±5km. 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.