Hartoog, O. E.O. E.HartoogMalesani, D.D.MalesaniFynbo, J. P. U.J. P. U.FynboD'Elia, ValerioValerioD'Elia2020-09-172020-09-172014-09-01https://hdl.handle.net/20.500.13025/3933eprint arXiv 1409.4804The reionisation of the universe is thought to have ended around z~6, as inferred from spectroscopy of distant bright background sources such as quasars (QSO) and gamma-ray burst (GRB) afterglows. Furthermore, spectroscopy of a GRB afterglow provides insight in its host galaxy, which is often too dim and distant to study otherwise. We present the high S/N VLT/X-shooter spectrum of GRB130606A at z=5.913. We aim to measure the degree of ionisation of the IGM between 5.02<z<5.84, and to study the chemical abundance pattern and dust content of its host galaxy. We measure the flux decrement due to IGM absorption at Ly$alpha$, $beta$ and $gamma$ wavelength regions. The hydrogen and metal absorption lines formed in the host galaxy are fitted with Voigt profiles to obtain column densities. Our measurements of the Ly$alpha$-forest optical depth are consistent with previous measurements of QSOs, but have smaller uncertainty than these. The Ly$alpha$ red-damping-wing analysis yields a neutral fraction $x_{HI}<0.03$ (3$sigma$). We obtain column density measurements of several elements. The ionisation corrections due to the GRB is estimated to be negligible (<0.03 dex), but larger corrections may apply due to pre-existing radiation field (up to 0.3 dex based on sub-DLA studies). Our measurements confirm that the Universe is already predominantly ionised over the redshift range probed in this work, but was slightly more neutral at z>5.6. GRBs are useful probes of the IGM ionisation state of the early Universe, but because of internal scatter we need a larger statistical sample to draw robust conclusions. The high [Si/Fe] in the host can be due to dust depletion, alpha-element enhancement or a combination. The very high value of [Al/Fe]=2.40+/-0.78 might be connected to the stellar population history. We estimate the host metallicity to be -1.5<[M/H]<-1.2 (3%-6% of solar). [truncated]Astrophysics - Astrophysics of GalaxiesAstrophysics - Cosmology and Nongalactic Astrophysicshttp://adsabs.harvard.edu/abs/2014arXiv1409.4804H2014arXiv1409.4804H