Turkish Journal of Physics, cilt.50, sa.1, ss.59-68, 2026 (ESCI, Scopus, TRDizin)
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.