GRB 201104B: VLT/X-shooter redshift
Abstract
We observed the optical afterglow (Marshall et al., GCN 28827) of GRB 201104B (Sbarufatti et al., GCN 28825) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-21000 AA, and consist of 2 exposures of 1200 s each. The observation mid-time was 2020 Nov 5.0831 UT (8.431 hr after the GRB). In a 60 s image taken with the acquisition camera on Nov 5.0596 UT, we detect the optical afterglow, for which we measure a magnitude r = 21.01 +/- 0.02 mag (AB magnitude, calibrated against nearby stars from the Pan-STARRS catalog; Chambers et al. 2016, arXiv:1612.05560). We clearly detect continuum over the entire wavelength range. A trough is visible around 3590 AA, which we identify as due to H I. From detection of multiple absorption features, which we interpret as due to SiII, CI, CII, SiIV, CIV, FeII, AlII, AlIII, MgII, we infer a redshift z = 1.954. In particular, fine structure lines from Fe II* are visible, which confirm the association of the absorption system with the GRB. Emission lines are also detected, which we interpret as due to [O II], [O III], ad Halpha at the same redshift. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Florian Rodler.
- Publication:
-
GRB Coordinates Network
- Pub Date:
- November 2020
- Bibcode:
- 2020GCN.28840....1V