{
  "bibcode": "2021GCN.29717....1D",
  "body": "A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. A. Kann \n(HETH/IAA-CSIC), D. B. Malesani (DTU Space), N. R. Tanvir (Univ. \nLeicester), C. Thoene, M. Blazek, J. F. Agui Fernandez (all \nHETH/IAA-CSIC), and S. Geier (GTC, IAC) report:\n\nWe observed the afterglow (Malesani et al., GCN #29703, Pozanenko et \nal., GCN #29708) of the short/hard GRB 210323A (Swift detection: Gropp \net al., GCN #29699, Fermi GBM detection: Hamburg & Meegan, GCN #29709; \nKonus-Wind detection: Frederiks et al., GCN #29713) with OSIRIS at the \n10.4m GTC telescope at Roque de los Muchachos Observatory, in La Palma \n(Spain). The observation started at 05:31 UT (0.3118 days after the \nburst), and consisted of 3 x 600s with grism R1000B, covering the \nspectral range from 3700 to 7800 AA. Observations were taken at high \nairmass, near dawn.\n\nThe 60 s acquisition image, with a seeing of 1\".3, shows the afterglow \nat a magnitude of r' = 23.03 +/- 0.15 mag, using a nearby Pan-STARRS \nfield star as photometric reference. This is in agreement with the NOT \nmeasurement.\n\nSpectral continuum is faintly detected above 5000 AA, and shows no clear \nevidence for any absorption or emission lines. We therefore place a weak \nupper limit of z < 3.1 on the redshift of GRB 210323A. There may be \nevidence for a low-significance emission line at 5110 AA, which is \nslightly offset from the continuum trace in the 2D spectrum. It is found \nusing multiple reductions and analyses. Interpreting this line as [OII], \nthe corresponding redshift would be z = 0.37. However, we do not find \nany evidence for other emission lines, such as Hbeta and [OIII], at the \ncorresponding redshift, placing its reality in doubt.\n\nFurther observations will be required to verify the reality of this \nfeature and to attempt a redshift determination through host galaxy \nspectroscopy.",
  "circularId": 29717,
  "createdOn": 1616615357000,
  "email": "kann@iaa.es",
  "subject": "Short GRB 210323A: GTC Observations",
  "submitter": "Alexander Kann at IAA-CSIC  <kann@iaa.es>",
  "eventId": "GRB 210323A"
}