Target classification with SPEEM. Left: QSO-Star separation based on the J-PLUS colors u−J0410 and J0378−g for a sample of 6794 stars. A threshold line at u−J0410 = 0.5 can be used to separate QSOs (pink filled circles) and stars (color-coded according to the spectral type). Right: distribution of classes (stellar spectral types and QSO) assigned by SEGUE for the studied sample.