[vsnet-grb-info 24899] GRB 200205B: VLT/X-shooter redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26998
SUBJECT: GRB 200205B: VLT/X-shooter redshift
DATE:    20/02/06 03:17:38 GMT
FROM:    Daniele B Malesani at DTU Space  <malesani at space.dtu.dk>

J.-B. Vielfaure (GEPI - Paris Observatory), D. Xu (NAO/CAS), J. Palmerio 
(GEPI - Paris Observatory), D. B. Malesani (DTU Space), L. Izzo 
(DARK/NBI), D. A. Kann (HETH/IAA-CSIC), A. J. Levan (Radboud Univ.), G. 
Pugliese (Univ. Amsterdam), N. R. Tanvir (Univ. Leicester) report on 
behalf of the Stargate collabaration:

We observed the optical afterglow of GRB 200205B (Evans et al., GCN 
26993) using the ESO VLT UT2 (Kueyen) equipped with the X-shooter 
spectrograph. Our spectra cover the wavelength range 3000-25000 AA, and 
consist of 4 exposures by 600 s each. The observation mid time was 2020 
Feb 6.063 UT (6.16 hr after the GRB).

In a 30 s image taken with the acquisition camera on Feb 6.041 UT, we 
detect the optical afterglow, for which we measure a magnitude r = 20.34 
+- 0.03 AB (calibrated against nearby stars from the SkyMapper catalog; 
Wolf et al. 2018, PASA, 35, 010; https:doi.org/10.4225/41/593620ad5b574).

We clearly detect continuum over the wavelength range 3100-24000 AA. 
 From detection of multiple absorption features, which we interpret as 
due to C ii, Si iv, Si ii, C iv, Fe ii, Al ii, Mg ii, we infer a 
redshift z = 1.465.
Emission lines are also detected, which we interpret as due to the [O 
ii] and [O iii] doublets, Hbeta, and Halpha, all at the above quoted 
redshift.

We acknowledge excellent support from the ESO observing staff in 
Paranal, in particular J. Corral-Santana and J. Velasquez.