Physical and dynamical characterization of (5201) Ferraz-Mello, a possible extinct Jupiter family comet ^*

¹ Observatório Nacional (COAA), rua Gal. José Cristino 77, São Cristóvão, CEP20921-400 Rio de Janeiro RJ, Brazil e-mail: carvano@on.br
² IAG, Universidade de São Paulo, rua do Matão 1226 CEP 05508-900 São Paulo SP, Brazil

Received: 20 March 2008
Accepted: 13 June 2008

Abstract

Context. The subject of asteroids in cometary orbits (ACOs) has been of growing interest lately. These objects have the orbital characteristics typical of comets, but are asteroidal in appearance, i.e., show no signs of a coma at any part of their orbits. At least a fraction of these objects are thought to be comets that have either exhausted all their volatile content or developed a refractory crust that prevents sublimation. In particular, the asteroid (5201) Ferraz-Mello has, since its discovery, been suspected to be an extinct Jupiter family comet due to the peculiar nature of its orbit.

Aims. The aim of this work is to put constraints on the possible origin of (5201) Ferraz-Mello by means of spectroscopic characterization and a study of the dynamics of this asteroid

Methods. We used the SOAR Optical Imager (SOI) to obtain observations of (5201) Ferraz-Mello using four SDSS filters. These observations were compared to asteroids listed in the Sloan Moving objects catalog and also to photometry of cometary nuclei, Centaurs, and TNOs. The orbital evolution of (5201) Ferraz-Mello and of a sample of asteroids and comets that are close to that object in the plane were simulated using a pure N-body code for 4 000 years forward and 4 000 years backward in time.

Results. The reflectance spectrum obtained from its colors in the SDSS system is unusual, with a steep spectral gradient that is comparable to TNOs and Centaurs, but with an increase in the reflectance in the g band that is not common in those populations. A similar behavior is seen in cometary nuclei that were observed in the presence of a faint dust coma. The dynamical results confirm the very chaotic evolution found previously and its dynamical similarity to the chaotic evolution of some comets. The asteroid is situated in the very stochastic layer at the border of the 2/1 resonance, and it has a very short Lyapunov time (30–40) years. Together, the spectral characteristcs and the dynamical evolution suggest that (5201) Ferraz-Mello is a dormant or extinct comet.