Analysing the database for stars in open clusters I. General methods and description of the data

TL;DR

This paper provides a comprehensive overview and statistical analysis of the WEBDA database, detailing data types, accuracy, and methods for deriving astrophysical parameters of open clusters, laying groundwork for future studies.

Contribution

It introduces a detailed methodology for analyzing diverse data sets in WEBDA and assesses their accuracy, facilitating future astrophysical parameter determination.

Findings

Over 97% of data exhibit sufficient accuracy for analysis

Compiled a list of deviating measurements for community use

Described data weighting and averaging methods

Abstract

We present an overview and statistical analysis of the data included in WEBDA. This database includes valuable information such as coordinates, rectangular positions, proper motions, photometric as well as spectroscopic data, radial and rotational velocities for objects of open clusters in our Milky Way. It also contains miscellaneous types of data like membership probabilities, orbital elements of spectroscopic binaries and periods of variability for different kinds of variable stars. Our final goal is to derive astrophysical parameters (reddening, distance and age) of open clusters based on the major photometric system which will be presented in a follow-up paper. For this purpose we have chosen the Johnson UBV, Cousins VRI and Stroemgren uvbybeta photometric systems for a statistical analysis of published data sets included in WEBDA. Our final list contains photographic, photoelectric and CCD data for 469820 objects in 573 open clusters. We have checked the internal (data sets within one photometric system and the same detector technique) and external (different detector technique) accuracy and conclude that more than 97% of all investigated data exhibit a sufficient accuracy for our analysis. The way of weighting and averaging the data is described. In addition, we have compiled a list of deviating measurements which is available to the community through WEBDA.