Asteroid shapes and thermal properties from combined optical and mid-infrared photometry inversion
1 Astronomical Institute, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
2 Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, 06304 Nice, France
3 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, Postfach 1312, 85741 Garching, Germany
Received: 24 March 2017
Accepted: 1 June 2017
Context. Optical light-curves can be used to reconstruct the shape and spin of asteroids. Because the albedo is unknown, these models are scale free. When thermal infrared data are available, they can be used to scale the shape models and derive the thermophysical properties of the surface by applying a thermophysical model.
Aims. We introduce a new method for simultaneously inverting optical and thermal infrared data that allows the size of an asteroid to be derived along with its shape and spin state.
Methods. The method optimizes all relevant parameters (shape and size, spin state, light-scattering properties, thermal inertia, and surface roughness) by gradient-based optimization. The thermal emission is computed by solving the 1D heat diffusion equation. Calibrated optical photometry and thermal fluxes at different wavelengths are needed as input data.
Results. We demonstrate the reliability and test the accuracy of the method on selected targets with different amounts and quality of data. Our results in general agree with those obtained by independent methods.
Conclusions. Combining optical and thermal data into one inversion method opens a new possibility for processing photometry from large optical sky surveys with the data from WISE. It also provides more realistic error estimates of thermophysical parameters.
Key words: minor planets, asteroids: general / radiation mechanisms: thermal / techniques: photometric
© ESO, 2017