10.3.4 Processing steps

The processing of classification included the following steps (see Rimoldini et al. 2023, for details):

1. 1.

   cross-match of Gaia sources with variable objects from the literature, as described in Gavras et al. (2023);

2. 2.

   ranking of literature catalogs according to their reliability, for each (sub)class;

3. 3.

   definitions of training sets:

   1. (a)

      selection of subsets of trustable representatives according to several diagnostics and maximising coverage across spacial, photometric, and astrometric parameters, for each (sub)class;

   2. (b)

      combination of the selected source subsets into different sets of classes and class groups (for training, validation, and test sets);

   3. (c)

      definition and selection of classification attributes;

4. 4.

   definitions of classifiers:

   1. (a)

      combination of (sub)classes according to physical and intrinsic classifier confusion for multi-class classifiers;

   2. (b)

      combination of all but one class for binary one-vs-rest classifiers;

   3. (c)

      tuning of classifier hyperparameters;

   4. (d)

      creation of multiple multi-class and one-vs-rest classifiers using the aforementioned Random Forest and XGBoost methods;

   5. (e)

      creation of meta-classifiers to combine multi-class classifiers that used different methods (improving the overall performance for all classes);

5. 5.

   verification and validation of results:

   1. (a)

      selection of results from up to 12 classifiers for each class or class group;

   2. (b)

      comparison with the literature;

   3. (c)

      generation of an overall classification score (best_class_score) for the verified classifications;

6. 6.

   selection of a single class for less than 1 % of the sources that were associated with multiple classes.

As in Gaia DR2, each classified source was associated with a single class and score. Classification results are available in the vari_classifier_result table and, as mentioned in Section 10.3.3, for the special case of galaxies, in the galaxy_candidates table.