Properties of the icy surface of the TNO 136108 (2003 EL{61})

Frédéric Merlin (1, 2) , Aurélie Guilbert (1, 2) , Christophe Dumas (3) , Maria Antonella Barucci (1, 2) , Catherine de Bergh (1, 2) , Pierre Vernazza (1, 2)

1 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
2 Pôle Planétologie du LESIA
3 European Southern Observatory

Context: Spectroscopic observations of numerous trans-Neptunian objects (TNOs), considered to be among the most pristine objects of the solar system, have revealed the presence of several kinds of surface ices. The high-sensitivity spectra that can be measured for the brightest objects also provide constraints on the physical properties of the surface (e.g. ice phase, temperature).
Aims: We observed one of the largest and brightest TNOs, 136108 (2003 EL{61}), to determine its surface composition properties and to constrain its surface properties.
Methods: We obtained new visible spectra with EMMI on the ESO-NTT and near-infrared spectra with the new 3D spectrograph SINFONI at the ESO-VLT. Our analysis consists of radiative transfer modelling to constrain composition and surface properties and to identify the precise minimum of the 1.65 micron band to constrain the surface temperature.
Results: The observations reveal a surface essentially composed of water ice. An absorption feature at 1.65 micron clearly indicates the presence of ice in the crystalline phase. Spectral modelling suggests that a small fraction of the surface ice is in the amorphous state. We also derive the temperature of the crystalline ice at the surface.

Domaines: Astrophysique [astro-ph]; Planète et Univers [physics]

Frédéric Merlin, Aurélie Guilbert, Christophe Dumas, Maria Antonella Barucci, Catherine de Bergh, et al.. Properties of the icy surface of the TNO 136108 (2003 EL{61}). Astronomy and Astrophysics - A&A, 2007, 466, pp.1185-1188. ⟨10.1051/0004-6361:20066866⟩. ⟨hal-03797059⟩