10.13.5 Quality assessment and validation
The cross-match between the rotational modulation variables detected in Gaia DR2 and in DR3 resulted in a sample of about 34 500 stars. About 100 000 bona fide rotational modulation variables listed in Gaia DR2 are not present in the DR3 catalogue. The main reason for this mismatch is that the chain of operators applied to the raw photometric time series (Section 10.2.3) removed a higher fraction of measurements than in Gaia DR2, at least for rotational modulation candidates. In fact, about 40 % of the missing variables did not pass the first selection criterion listed in Section 10.13.2. An extensive discussion on the differences between the Gaia DR2 and DR3 rotational modulation catalogue is presented in Distefano et al. (2023). In Figure 10.33, we show the comparison between the Gaia DR2 and DR3 best_rotation_period values for the cross-matched sources. For about 60 % of the sample, the difference between the Gaia DR2 and DR3 periods is less than 5 % and, for about 20 % of the sample, it is between 5 and 20 %. Period differences of up to 20 % are acceptable because they are at the level of those induced by the surface differential rotation, as discussed in Distefano et al. (2016).
The cross-match between the rotational modulation variables in Gaia DR3 and the ones identified in the Zwicky Transient Facility (ZTF) Catalogue of Periodic Variable Stars (Chen et al. 2020) resulted in a sample of about 5450 sources. Figure 10.34 shows the comparison between Gaia DR3 and ZTF rotation periods. For 55 % of these stars, the difference between the periods detected in both surveys is less than 5 %. For 18 % of the sample, the ZTF periods differ by less than 5 % from the loci marked with the blue, red, and black lines. The blue lines mark the loci corresponding to half and twice the Gaia DR3 periods. The red and black lines correspond to the loci of the aliased periods associated with the 1 and 2 d cadence of the ZTF time series, respectively. Overall, in 92 % of the cases, the Gaia DR3 periods differ by less than 20 % from the ZTF periods or the loci high-lighted in Figure 10.34.