A. Cellino, S. Bagnulo, R. Gil-Hutton, P. Tanga, M. Cañada-Assandri, & E.F. Tedesco

On the calibration of the relation between geometric albedo and polarimetric properties for the asteroids

Figure 1. Examples of phase - polarization curves obtained for four large main belt asteroids belonging to different taxonomic classes: top left: the dwarf planet (1) Ceres (G-class); top right: (4) Vesta (V -class); Bottom left: (6) Hebe (S-class); bottom right: (21) Lutetia (for a long time considered to belong to the old M class, now included in the X complex). Open symbols refer to data available in the literature. Full symbols in the plots iden- tify observations obtained at the CASLEO observatory. Most of them have been published only recently (Gil Hutton et al. 2014). The best-fit lines correspond to the exponential-linear relation discussed in Sect. 5.

Abstract

We present a new extensive analysis of the old problem of finding a satisfactory calibra- tion of the relation between the geometric albedo and some measurable polarization properties of the asteroids. To achieve our goals, we use all polarimetric data at our disposal. For the purposes of calibration, we use a limited sample of objects for which we can be confident to know the albedo with good accuracy, according to previous investigations of other authors. We find a new set of updated calibration coefficients for the classical slope - albedo relation, but we generalize our analysis and we consider also alternative possibilities, including the use of other polarimetric parameters, one being proposed here for the first time, and the possibility to exclude from best-fit analyzes the asteroids having low albedos. We also consider a possible parabolic fit of the whole set of data

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Last Revised: 2015 June 1st