7.4.4 Processing steps

The processing includes the following steps common to both RR Lyrae and Cepheid stars (see Fig. 1 in Clementini et al. 2018):

  1. 1.

    Derivation of period and harmonics (amplitudes and phases) by non-linear Fourier analysis,

  2. 2.

    Measurement of light curve parameters (mean magnitudes, amplitudes, epochs of maximum light, etc.),

  3. 3.

    Consistency check of the periods derived from the 3 bands (G, GBP, GRP),

  4. 4.

    Search for secondary periodicities.

The following additional steps are then applied to sources confirmed as RR Lyrae stars (see Fig. 2 in Clementini et al. 2018):

  1. 1.

    RR Lyrae Double-mode search,

  2. 2.

    Non-linear double-mode modelling,

  3. 3.

    Amplitude ratios,

  4. 4.

    Mode identification,

  5. 5.

    RR Lyrae Classification and validation,

  6. 6.

    Stellar parameters derivation: metallicity,

  7. 7.

    Stellar parameters derivation: absorption in the G-band for RRab stars.

and the following additional steps applied to sources confirmed as Cepheid variables (see Fig. 3 in Clementini et al. 2018):

  1. 1.

    Cepheid Multimode search,

  2. 2.

    Cepheid Type identification,

  3. 3.

    Type II Cepheid Subclassification,

  4. 4.

    δ Cepheid Mode identification,

  5. 5.

    ACEP Mode identification,

  6. 6.

    Cepheid Classification and validation,

  7. 7.

    Stellar parameters derivation: metallicity for δ Cepheid variables with period shorter than about 6 days.