Polarimetric rotational curve of M-type asteroid (16) Psyche

We present the polarimetric measurements of the asteroid (16) Psyche for its whole rotational phase. Observations were conducted in the facilities of the OAN-SPM with a double beam polarizer (POLIMA 2) coupled to the 84 cm telescope in September 2019. Polarimetric lightcurves are valuable because they might provide useful information about the geometric albedo and surface properties of atmosphereless bodies.

The upcoming NASA mission to visit Psyche will verify most of the ground-based observations, however, there is a lack of polarimetric lightcurves, which could be useful for a more precise determination of the surface properties.

Polarimetry relies on relative flux variation of orthogonal polarization states to determine Stokes parameters. The aim, in this work, is to measure the amount of linearly polarized light reflected by the asteroid (16) Psyche.

The polarimetric lightcurve was obtained for a rotation period, and an amplitude of 0.14 ± 0.03% was measured for a phase angle of ∼ 17 °. From a comparison between the polarization curve with the corresponding photometric lightcurve, we found that the latter is possibly affected by both albedo and shape.

Our results show evidence of albedo variegation, which is in agreement with the albedo map of (16) Psyche obtained with different observational techniques.