TITLE:   GCN CIRCULAR
NUMBER:  12494
SUBJECT: GRB 111022B: 10.4m GTC z'-band observations
DATE:    11/10/25 10:15:40 GMT
FROM:    Javier Gorosabel at IAA-CSIC  <jgu@iaa.es>

J. Gorosabel (IAA-CSIC), A. Cabrera Lavers (GTC), R. Sanchez-Ramirez  
(IAA-CSIC), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), A.J. Levan (U.  
Warwick), C.C. Thoene (IAA-CSIC), N.R. Tanvir (U. Leicester), A.J.  
Castro-Tirado (IAA-CSIC), P. Kubanek (IAA-CSIC, U. Valencia), report  
on behalf of a larger collaboration:

We acquired z'-band images of the GRB 111022B field (Holland et al.,  
GCNC 12472; Beardmore et al., GCNC 12478) with the 10.4m GTC(+OSIRIS)  
telescope. The observations were carried out on Oct 24.1105--24.1453  
UT (33.4--34.3 hours post GRB) with a total exposure time of  
31x60s=1860s and a seeing of 1.0-1.5". A faint object is detected  
coincident with the near-IR and optical candidate (Levan et al.  GCNC  
12481; Moskvitin et al. GCNC 12491). This source has a very  
preliminary AB magnitude of  z'~25.5. In the XRT error circle  
(Beardmore et al., GCNC 12478) we note the presence of an additional  
object with a similar magnitude located 1.5" eastwards from the  
afterglow candidate.