EROS-2 light curves (top and middle) of two variable stars crossmatched with the OGLE RRLs. Top: raw light curves, middle: phase-folded light curves, left: one RRL variable included in the training set, and right: another RRL variable excluded from the training set. The x-axis of raw light curves is in the unit of Heliocentric Julian Date (HJD) – 2 450 000. We use this unit as the unit of x-axis for a raw light curve throughout this paper. Periods shown in the top panels are derived using the Lomb-Scargle algorithm (Lomb 1976). In the bottom two panels, we show the phase-folded OGLE light curves of the same RRLs. The periods of these light curves are taken from Soszyński et al. (2009b). Although the OGLE RRL in the bottom-right panel shows clear periodic signals, the crossmatched EROS-2 counterpart’s light curve (top right and middle right) does not show any variability, which is associated with blending with a nearby star. See text for details.