TITLE:   GCN CIRCULAR
NUMBER:  22555
SUBJECT: GRB 180325A: VLT/X-shooter spectroscopic observations
DATE:    18/03/27 21:30:43 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <paolo.davanzo@brera.inaf.it>

P. D’Avanzo (INAF-OAB), J. Bolmer (ESO/MPE), V. D’Elia (ASI-SSDC), J. P. U. Fynbo (DAWN/NBI), K. E. Heintz (U. Iceland, DAWN/NBI), L. Izzo (HETH/IAA-CSIC), J. Japelj (API, U. Amsterdam), D. A. Kann  (HETH/IAA-CSIC), D. Malesani (DAWN/NBI and DARK/NBI), J. Selsing (DARK/NBI), N. R. Tanvir (Univ. Leicester), T. Zafar (AAO), S. Campana (INAF-OAB), A. de Ugarte Postigo (HETH/IAA-CSIC and DARK/NBI), J. Hjorth (DARK/NBI), L. Kaper (Univ. Amsterdam), A. Melandri (INAF-OAB), A. Smette (ESO), report on behalf of the Stargate Consortium:

We observed the optical afterglow of GRB 180325A (Troja et al. GCN 22532) with the ESO VLT/X-shooter spectrograph, covering the wavelength range 3000-25000 AA. Spectroscopy started at 03:20:45 UT on 2018-03-25 (i.e., ~1.5 hr after the GRB) and consisted of 8 exposures of 600 s.

The spectrum exhibits a red continuum with several absorption features, including Ly-alpha and different metal and fine-structure lines, together with [OII], [OIII] and Halpha emission lines, all at a common redshift of z=2.248. At the same redshift, we also note the presence of a clear continuum depression corresponding to the 2175 AA bump. Finally, the spectrum shows the presence of a strong double intervening system at z = 2.041/2.043. 

The above results are in agreement with the findings of Heintz et al. (GCN 22535). 


We acknowledge the excellent support from the ESO staff, particularly Luca Sbordone, Jose Velasquez and Zahed Wahhaj in obtaining these observations.