Multi-epoch X-ray time series of RBS 1332. The soft X-rays show a significant variability compatible with flux changes observed above 2 keV. The ratios between hard and soft X-rays also exhibit changes on ks timescales, especially in observations 2 and 5, see the Sect. 2 for model details. Black, red, green, blue, magenta, and cyan colours refer to obs. 1, 2, 3, 4, and 5, respectively. This colour code is adopted throughout the whole paper.