L. Izzo (HETH/IAA-CSIC), K. E. Heintz (Univ. Iceland and DAWN/NBI), D. Malesani (DAWN/NBI and DARK/NBI), B. Milvang-Jensen (DAWN/NBI), N.R. Tanvir (Univ. Leicester), D.A. Perley (LJMU), A. de Ugarte Postigo (HETH/IAA-CSIC and DARK/NBI), J.P.U. Fynbo (DAWN/NBI), D.A. Kann (HETH/IAA-CSIC) report on behalf of the Stargate Consortium:
We observed the optical afterglow of GRB 180329B (Racusin et al. GCN 22558, Perley et al. GCN 22562) with the ESO VLT/X-shooter spectrograph, covering the wavelength range 3000-21000 AA. Spectroscopy started at 00:10:12 UT on 2018-03-30 (~10 hours after the GRB trigger) and consisted of 2 exposures of 600 s.
Preliminary analysis of the spectrum reveals absorption lines of O I 1302, C IV 1548/50, Al II 1670, Fe II 2344, 2374, 2382, 2586, 2600, Mg II 2796/2803 and Mg I 2853 at a common redshift of z=1.998. This is consistent with a broad absorption seen in the UVB arm spectrum at ~3635 AA, due to a damped Lyman-alpha feature. We therefore propose this to be the redshift of the GRB.
We acknowledge the excellent support from the ESO staff, particularly Marcela Espinoza, Luca Sbordone, Eleonora Sani and Pascale Hibon in obtaining these observations.