Bottom panel: timing residuals of all NICER IGR J17591−2342 pulse template arrival times (in phase units) with respect to the best phase-coherent model (=constant frequency; see Table 1 ) for segment-3, which covers MJD 58370–58383 (green band/data points). Deterministic (segment-1, covering MJD 58345–58364, blue band/data points) as well as more noisy/erratic segments (e.g. segment-2 from MJD 58364–58370 and segment-4 for data beyond MJD 58383) are shown too. In orange, yellow and red the two NuSTAR, Chandra and XMM-Newton ToO’s are indicated, respectively. Top panel: data points and dashed line show the shape of the NICER 1–10 keV daily averaged count rate.