Radiative loss functions considered in this work. Solid line: power-law segments function, equal to    T² (for log T < 4.95 K) and    T^-1 (for log T > 4.95 K); solid line plus star symbols: a peak mimicking the H Ly-α losses was added to the previous function; dashed line: from Cook et al. (1989), but with a T³ dependence below T = 10⁵ K; long-dashed line: from Colgan et al. (2008); dotted line: from Dere et al. (2009); dot-dashed line: from Dere et al. (2009) without the H contribution.