{
  "submittedHow": "web",
  "submitter": "Ines Francesca Giudice <ines.giudice@inaf.it>",
  "bibcode": "2025GCN.41289....1G",
  "body": "I. F. Giudice (INAF/OACn), M. Garnichey (LUX-Paris Obs.), A. L. Thakur (INAF-IAPS), A. Saccardi (CEA/Irfu), L. Izzo (INAF/OACn & DARK/NBI), A. Martin-Carrillo (UCD), M. De Pasquale (U.Messina), N. R. Tanvir (U. Leicester), S. D. Vergani (LUX-Paris Obs.), D. B. Malesani (DAWN/NBI and Radboud Univ.), report on behalf of the Stargate collaboration:\n\nWe observed the optical counterpart (Kingler et al., GCN 41268; van Dalen et al., GCN 41278) of GRB 250807B detected by Swift with ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-21000 A, and consist of 4 exposures of 600 s each. Observation started on 2025-08-08 at 08:42:42 UTC (17 hours after trigger).\n\nIn a preliminary reduction of the spectra, we identify several absorption features, which we interpret as Fe II, the Mg II doublet, and Mg I, from which we derive a redshift of z = 1.522. We notice the absence of emission or fine-structure lines. The presence of a continuum in the UVB arm supports the interpretation that this could be the GRB redshift.\n\nThe analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495).\n\nWe acknowledge excellent support from the ESO observing staff in Paranal.\n",
  "eventId": "GRB 250807B",
  "subject": "GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522",
  "format": "text/plain",
  "createdOn": 1754663418575,
  "circularId": 41289
}