Simultaneous visible-near IR photometric study of Kuiper Belt Object surfaces with the ESO/Very Large Telescopes^*

¹ Observatoire de Paris-Meudon – LESIA, 5 Place Jules Janssen, 92195 Meudon cedex, France e-mail: Audrey.Delsanti@obspm.fr
² ESO/Chile – European Southern Observatory, Casilla 19001, Santiago 19, Chili e-mail: ohainaut@eso.org
³ Centre de Recherche Astronomique de Lyon, 9, Av. Charles André, 69561 St-Genis Laval, France e-mail: emilie@obs.univ-lyon1.fr
⁴ Institute for Astronomy, 2680 Woodlawn Drive, 96822 Honolulu, Hawaii, USA e-mail: meech@ifa.hawaii.edu
⁵ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany e-mail: hboehnha@mpia-hd.mpg.de
⁶ Universidad Catolica del Norte, Avenida Angamos 0610, Casilla 1280, Antofagasta, Chile e-mail: lbarrera@ucn.cl

Corresponding author: A. Delsanti, Audrey.Delsanti@obspm.fr

Received: 12 August 2003
Accepted: 9 December 2003

Abstract

We present simultaneous visible-near-IR (BVRIJHK) photometry of 8 Kuiper belt objects (KBOs) and 4 Centaurs. The observations were carried out using two 8m-units of the ESO/Very Large Telescope operated simultaneously on November 29 and 30, 2000. The KBOs displayed linear reflectivity spectra in the optical with a wide range of slopes from neutral (solar) to very red. In most cases, the reflectivity spectra are linear from B to J bands. We notice a change of regime in the spectra which flatten toward the H and K bandpasses. (33128) 1998 BU₄₈ even has a significantly negative value. Only (54598) 2000 QC₂₄₃ does not flatten in the infra-red. (24835) 1995 SM₅₅ has a noticeably blue spectrum in the near-IR which might be indicative of water ice absorption features. We also present an empirical model for KBO surface evolution, based on models from [CITE] and [CITE], in which surface colors evolve because of collisions. In the model presented here we propose that cometary activity can refresh the surface. This model predicts that (1) small (e.g. ≪80 km in radius) KBOs should have color variations with rotation, (2) the larger objects should display uniform colors, (3) there should be no color dependence with inclination for objects >100 km in radius, and (4) very distant KBOs are fully irradiated.