7.4.1. *L* iso–*τ*lag Correlation

As established in Ref. [147], this correlation holds also for X-ray flares (in the rest frame energy band 0.3–10 keV) and proposed that their underlying mechanism is similar. However, this correlation is affected by evolution effects, as discussed in Ref. [130].

One of the latest proposed explanations of the *L*iso–*τ*lag correlation involves only kinematic effects [148], as the observed time-lag is *<sup>τ</sup>*lag <sup>∝</sup> <sup>D</sup>−<sup>1</sup> and the luminosity is *L*iso ∝ D, where D is the Doppler boost defined in Section 3.1.5.

As discussed in Ref. [149], this correlation was constructed from a small sample of heterogeneously collected GRBs and is severely affected by sample incompleteness.
