Erratum: Hanbury Brown–Twiss Interferometry at a Free-Electron Laser [Phys. Rev. Lett. 111, 034802 (2013)]

Figure 3

(a) Contrast (points) ${\zeta }_2(D_{\omega })=g^{(2)}(0)-1$ as a function the coherence time ${\tau }_c$. The error bars are the same as in Figs. 2(c) and 2(d). Theoretical fit (solid line) corresponds to a pulse duration of $T=31\pm 13\mathrm{fs}$.