V. Alí-Lagoa^1,2, L. Lionni³, M. Delbo⁴, B. Gundlach⁵, J. Blum⁵ and J. Licandro^1,2

¹Instituto de Astrofísica de Canarias (IAC), c/ Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
²Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
³University Paris VII – Diderot, 5 rue Thomas Mann, 75013 Paris, France
⁴UNS-CNRS-Observatoire de la Côte d’Azur, BP 4229, 06304 Nice Cedex 4, France
⁵Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany

Aims. We derive the thermal inertia of 2008 EV₅, the baseline target for the Marco Polo-R mission proposal, and infer information about the size of the particles on its surface.
Methods. Values of thermal inertia were obtained by fitting an asteroid thermophysical model to NASA’s Wide-field Infrared Survey Explorer (WISE) infrared data. Grain size was derived from the constrained thermal inertia and a model of heat conductivity that accounts for different values of the packing fraction (a measure of the degree of compaction of the regolith particles).
Results. We obtain an effective diameter D = 370 ± 6   m, geometric visible albedo p_V = 0.13 ± 0.05 (assuming H = 20.0 ± 0.4), and thermal inertia Γ = 450 ± 60 J m^-2 s^−1/2 K^-1 at the 1σ level of significance for its retrograde spin-pole solution. The regolith particles radius is r = 6.6^+1.3_-1.3 mm for low degrees of compaction and r = 12.5^+2.7_-2.6 mm for the highest packing densities.

Reference
Alí-Lagoa V, Lionni L, Delbo M, Gundlach B, Blum J and Licandro J (2014) Thermophysical properties of near-Earth asteroid (341843) 2008 EV₅ from WISE data. Astronomy & Astrophysics 561:A45.
[doi:10.1051/0004-6361/201322215]
Reproduced with permission © ESO

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