[vsnet-grb-info 20725] GRB 180620B: VLT/X-shooter redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22823
SUBJECT: GRB 180620B: VLT/X-shooter redshift
DATE:    18/06/22 13:02:56 GMT
FROM:    Maryam Arabsalmani at CEA Paris-Saclay  <maryam.arabsalmani at cea.fr>

L. Izzo (HETH/IAA-CSIC), M. Arabsalmani (CEA Saclay), D. B. Malesani (DAWN/NBI and DARK/NBI), K. Wiersema (Warwick), G. Pugliese (API/U. Amsterdam), S. D. Vergani (GEPI/Obs. Paris), A. de Ugarte Postigo (HETH/IAA-CSIC and DARK/NBI), K. E. Heintz (Univ. Iceland and DAWN/NBI), D.A. Kann (HETH/IAA-CSIC), P. Schady (MPE), N.R. Tanvir (Leicester), J.P.U. Fynbo (DAWN/NBI), C. C. Thoene (HETH/IAA-CSIC), J. Bolmer (MPE Garching), report on behalf of the Stargate Consortium:

We observed the optical afterglow of GRB 180620B (Evans et al. GCN 22807; Schweyer & Schady GCN 22819) using the ESO Very Large Telescope (VLT) UT2 equipped with the X-shooter spectrograph. Spectroscopic observations started on 09:27 UT on 21 June 2018, i.e. 0.73 days after burst. In the resulting spectrum, we find a series of strong absorption lines that we identify as Fe II, Mg II, Mg I, Zn II, Cr II, Al II and Al III at a common redshift of 1.1175. At this redshift, we also detect emission lines of [O II], [Ne III] and Balmer lines. Both absorption and emission lines show velocity structure. The absorption profiles are broad and spread over more than 800 km/s in velocity space.

We are grateful to the visiting observers, Jean-Christophe Loison and Pedro Machado, for giving up some of their observing time. We thank the ESO staff, Marcela Espinoza and Alain Smette, for excellent support.