Asteroid phase curve parameters from Gaia photometry

Asteroids have remained mostly the same for the past 4.5 billion years, and provide us information on the origin, evolution and current state of the Solar System. For the physical characterization of asteroids, one of the best data sources is photometry: the measurement of the disk-integrated brightness of the asteroid.  An asteroid's lightcurve (i.e. the dependency of the brightness as a function of time) is indicative of its surface scattering properties, as well as its shape and the state of spin. 

In this work, we apply novel Bayesian inverse methods (Muinonen et al., A&A 2020, in revision) to derive phase curve parameters from photometric lightcurve observations. Our aim is to validate and expand the existing analyses by applying the methods to of the order of tens to hundreds of asteroids using photometric data from the Gaia Data Release 2 (Gaia Collaboration, Spoto et al., A&A 616, A13, 2018) and ground-based photometry (Durech et al., A&A 513, A46, 2010) from Database of Asteroid Models from Inversion Techniques (DAMIT). We derive phase curve linear slopes by using four techniques:  1) convex inversion on all data, 2) convex inversion on all data with fixed rotation parameters from DAMIT, 3) ellipsoid inversion on Gaia DR2 data only, and 4) ellipsoid inversion on Gaia DR2 data only with fixed rotation parameters from DAMIT. Finally, we compare the obtained slope parameters with the presumed Bus-DeMeo (DeMeo et al., Icarus 202, 160, 2009) taxonomic classes of the asteroids, and study possible correlations with the geometric albedos. The Gaia photometry has milli-magnitude precision and is thus extremely valuable when used to carry out asteroid taxonomic classification.