[vsnet-grb-info 15236] GRB 140705A / SGR 1935+2154: Optical observations from 10.4m GTC

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16528
SUBJECT: GRB 140705A / SGR 1935+2154: Optical observations from 10.4m GTC
DATE:    14/07/06 03:47:32 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte at iaa.es>

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), J. Gorosabel (IAA-CSIC/UPV-EHU), P. Rodriguez-Gil (IAC) and S. Campana (INAF-OAB) report on behalf of a larger collaboration:

We have observed the field of GRB 140705A / SGR 1935+2154 (Stamatikos et al. GCN 16520, Lien et al. GCN 16522) using OSIRIS on the 10.4m GTC telescope. Observations started at 00:57 UT of the 6 July 2014 (15.42 hrs after the burst onset) and consisted of 10x120s in i-band and 20x60s in z-band. Within the enhanced XRT error box (Osborne et al. GCN 16521, updated to R.A.: 293.73169, Dec.: +21.89668, +/-1.5") we detect two sources. The first of them, which we name S1, has an approximate magnitude of i(AB)~24 whereas S2 has i(AB)~25.5. Photometry is based on USNO-B1.0, and is still very preliminary. The coordinates of these sources are (J2000+/-0.5"): 

S1: 19:34:55.56, +21:53:48.2
S2: 19:34:55.68, +21:53:47.9

We have used UKIDSS nIR images for comparison, as there were not deep enough images available in the optical (there is no SDSS coverage in this field). S1 is clearly detected in J, H and K-band images of UKIDSS. S2, could be marginally detected in J-band. At this point we cannot claim variability of any of these sources and thus their relation with GRB 140705A / SGR 1935+2154 cannot be stated.

We acknowledge excellent support from the GTC staff, in particular Riccardo Scarpa.