We present a detailed analysis of the long-term X-ray light curve of 4U 1608–52, focusing on fast-rising exponential-decay (FRED) outbursts, low-intensity states, and quiescent intervals. By calibrating the onset times of the outbursts, we identify three distinct classes for the FRED-type events: (i) the long-high outbursts, exceeding ~50 d in duration with peak count rates above ~40 cnt s-1; (ii) the short-medium outbursts, with durations of ~20 d and peak count rates of ~30-50 cnt s-1; and (iii) the short-low outbursts, also lasting ~20 d but reaching only ~20-30 cnt s-1 at peak. Furthermore, we examine the relation between preoutburst duration and the peak and integrated count rates of the upcoming outburst. We show that outbursts following longer quiescent periods tend to be more energetic.
Can Güngör (2026) studied this question.