Fundamental parameters for 45 open clusters with Gaia DR2, an improved extinction correction and a metallicity gradient prior

Reliable fundamental parameters of open clusters (OCs) such as distance, age, and extinction are key to our understanding of Galactic structure and stellar evolution. In this work, we use Gaia Data Release 2 (DR2) to investigate 45 OCs listed in the New catalogue of optically visible open clusters and candidates (DAML) but with no previous astrometric membership estimation based on Gaia DR2. In the process of selecting targets for this study, we found that some clusters reported as new discoveries in recent papers based on Gaia DR2 were already known clusters listed in DAML. Cluster memberships were determined using a maximum likelihood method applied to Gaia DR2 astrometry. This has allowed us to estimate mean proper motions and mean parallaxes for all investigated clusters. Mean radial velocities were also determined for 12 clusters, 7 of which had no previous published values. We have improved our isochrone fitting code to account for interstellar extinction using an updated extinction polynomial for the Gaia DR2 photometric bandpasses and the Galactic abundance gradient as a prior for metallicity. The updated procedure was validated with a sample of clusters with high-quality [Fe/H] determinations. We then did a critical review of the literature and verified that our cluster parameter determinations represent a substantial improvement over previous values.