TITLE:   GCN CIRCULAR
NUMBER:  15426
SUBJECT: GRB 131031A: 1.23m CAHA afterglow candidate
DATE:    13/11/01 08:48:12 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

J. Gorosabel (IAA-CSIC,UPV/EHU), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), 
V. Terron (IAA-CSIC) report on behalf of a larger collaboration:

Further analysis of the observations of the field of GRB 131031A (Cummings 
GCN 15421) obtained with the 1.23m CAHA in I-band, 10.2 hr after the burst 
(Terron et al. GCN 15422), reveals a source consistent with the XRT afterglow 
candidate at the following coordinates (J2000+/-0.5"):

R.A.: 01:58:26.46
Dec: -01:34:48.1

This source is not present in the archival SDSS images and has a magnitude of 
i(AB)=21.63+/-0.25 as compared with SDSS field stars. Thus, we propose it as 
the optical afterglow of GRB 131031A. Further observations will be needed to 
check for variability.