GCN Circular 31800
A. de Ugarte Postigo (Artemis/OCA), B. Schneider (CEA Paris-Saclay), D. B. Malesani (Radboud Univ. and DAWN/NBI), D. A. Kann (IAA-CSIC) report on behalf of the Stargate collaboration: We observed the location of the ultra-long GRB 211024B (Gropp et al. GCN 30980, Zhu et al. GCN 30984) using the X-shooter spectrograph mounted on the UT3 of ESO���s Very Large Telescope. The observation was performed on 27 March 2022 (153 days after the GRB) and consisted of 4x1200 s in the UVB and VIS arms and 8x600 s in the NIR arm. We used the JH-slit that blocks part of the K-band and in return increases the efficiency of the J and H bands, resulting in a wavelength coverage between 3000 to 21000 AA. In a preliminary reduction we detect two weak emission lines that we identify as [OII]3727 and [OIII] 5008, as well as a marginal detection of [OII]4960 at a common redshift of z=1.1137+/-0.0002. The other line of the OII doublet, [OII]3729 is affected by a sky line and is consequently not detected. H-alpha falls within a telluric absorption and H-beta in a spectral region of low sensitivity, both resulting in non detections. Given the spatial coincidence of these emissions with the afterglow, we identify the underlying object as the host galaxy and propose this as the redshift of the GRB. We acknowledge expert support from the ESO staff in Paranal, in particular Cedric Ledoux and Michael Abdul-Masih.