{
  "bibcode": "2019GCN.25653....1L",
  "body": "A.J. Levan (Radboud), P.G. Jonker (SRON/Radboud), P. Rodriguez Gil, M.A.P.\nTorres (IAC/ULL), K. Maguire (TCD), M. Fraser (UCD), D. Mata (JBCA, University\nof Manchester) report on behalf of a larger collaboration:\n\nWe obtained 3x900 sec of spectroscopic observations of ZTF19abvizsw with the GTC on La Palma on 2\nSeptember 2019 over the time interval 20:37 - 22:05 UT  using the R1000R grating and the OSIRIS\ninstrument. The spectra cover the range 5100-10000 AA. A strong continuum is detected with\nprominent absorption lines which we identify as FeII (2344, 2374, 2383, 2586, 2600 AA) and MgII\n(2796, 2803 AA) and MgI (2852 AA) at a common redshift of z=1.258. This is in agreement with the\nresults of Burdge et al. (GCN 25639). Indeed the spectral features provide a good match to the\ncomposite spectra of GRB afterglows (Christensen et al. 2011).  This offers further support for\nthe identification of ZTF19abvizsw as an untriggered GRB (Perley et al. GCN 25643). Searches in\nexisting gamma-ray observations around the rise time would be strongly merited. \n\n\nWe thank the GTC staff and especially Peter Pessev for their assistance in\nacquiring these observations.\n\nAcknowledgements: PGJ acknowledges support from the European Research\nCouncil under ERC Consolidator Grant agreement no 647208.",
  "circularId": 25653,
  "createdOn": 1567597484000,
  "email": "p.jonker@sron.nl",
  "subject": "LIGO/Virgo S190901ap: GTC follow-up spectroscopic observations of ZTF19abvizsw",
  "submitter": "Peter Jonker at SRON/RU  <p.jonker@sron.nl>",
  "eventId": "LIGO/Virgo S190901ap"
}