Characterizing asteroid (152830) Dinkinesh in preparation for the encounter with the NASA Lucy mission: a photometric study

Main Belt asteroid (152830) Dinkinesh will be the first fly-by target of the Lucy mission on 2023 November 1, during its cruise to the Trojan clouds. We report our photometric time series observations of this target performed on 14 nights over nearly three months during the 2022-23 apparition with the 1.23-m telescope at Calar Alto, Spain, aimed at determining its rotation and photometric properties. We find that Dinkinesh is a slow rotator (P-syn = 52.67 +/- 0.04h) with a moderately large light-curve amplitude (A = 0.39 +/- 0.02), which implies an axial ratio a/b greater than or similar to 1.43. Its photometric parameters in the HG-system are H-R = 17.17 +/- 0.04 and G(R) = 0.378 +/- 0.035 with a colour index = 0.455 +/- 0.025. A fit to the IAU system results in = 17.17 +/- 0.14; G(1) = 0.37 +/- 0.17 and G(2) = 0.43 +/- 0.04. Assuming that Dinkinesh's albedo lies within +/- 2 sigma of the average value for small S-class asteroids, its spherical surface-equivalent diameter is between 0.66 and 1.36km.