Outburst characteristics of transient  low-mass X-ray binary 4U 1608-52

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.