{
  "bibcode": "2018GCN.22591....1S",
  "body": "J. Selsing (DARK/NBI), D. Malesani (DAWN/NBI and DARK/NBI), D.A. Kann \n(HETH/IAA-CSIC), N.R. Tanvir (Univ. Leicester) report on behalf of the \nStargate consortium:\n\nWe observed the optical counterpart of GRB 180404A (Gropp et al., GCN  \n22589) using the ESO Very Large Telescope (VLT) UT2 equipped with the \nX-shooter spectrograph. Observations were carried out in robotic \"rapid \nresponse mode\" (RRM), initiated automatically following the X-ray \nlocalization notice.\n\nIn the 15-s r-band acquisition image, taken on 2018 Apr 4.0423 UT (15.3  \nmin after the trigger), the afterglow is clearly detected, at \ncoordinates (J2000):\n\nRA = 05:34:11.67\nDec = -37:10:04.1\n\nWe measure a magnitude R = 18.64 +- 0.1 (Vega), calibrated against \nnearby USNO stars, where the error is dominated by the calibration scatter.\n\nSeveral spectra were acquired. We report here on the exposure with mid \nepoch Apr 4.0495 UT (that is, 25.6 min after the GRB), with 600 s \nexposure time, and covering the wavelength range 3000-25000 AA. The \nafterglow continuum trace is clearly detected. Superposed on it, several \nabsorption features are visible, which we identify as Al III, Fe II, Mg \nII, and Mg I, all at a common redshift redshift of z = 1.000.\n\nWe acknowledge excellent support from the observing staff at Paranal, in \nparticular Stephane Brillant, Luca Sbordone, Andrea Mehner, and Jose \nVelasquez.",
  "circularId": 22591,
  "createdOn": 1522811744000,
  "email": "malesani@dark-cosmology.dk",
  "subject": "GRB 180404A: VLT/X-shooter redshift",
  "submitter": "Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@dark-cosmology.dk>",
  "eventId": "GRB 180404A"
}