X-ray temperature versus luminosity. Left panel: temperature versus X-ray luminosity for the XMM-Newton subsample used in this work (black solid line) in comparison with the literature. The terms BC and NC indicate bias-corrected and non-corrected relations, respectively, while TL and CEL are total and core-excised L_X, respectively. The abbreviations TT and CET are for total and core-excised kT, respectively. The type of the sample used and the regression method are also indicated (see Sect. 4.5 for more details). Grey and black points are high and low concentration groups, respectively, defined at c₂₀₀ = 2. The shaded region is the 1-σ uncertainty. Right panel: comparison of the slope of the kT–L_X relation with the literature. Slope labels are the same as relation labels from the left panel. Only band-limited L_0.1–2.4 relations are considered.