[vsnet-grb-info 13376] GRB 130527A: NOT optical counterpart

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14710
SUBJECT: GRB 130527A: NOT optical counterpart
DATE:    13/05/28 16:42:36 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani at dark-cosmology.dk>

Z. Cano (U. Iceland), D. Malesani (DARK), N. R. Tanvir (U. Leicester), 
D. Xu (DARK/NBI), T. Kangas (U. Turku), and J. Kajava (NOT) report on 
behalf of a larger collaboration:

On 2013 May 28, beginning at 03:55 UT, we observed the field of GRB 
130527A (Gompertz et al., GCN 14703) with the Nordic Optical Telescope 
(NOT) equipped with the ALFOSC instrument using the z filter, for a 
total exposure time of 40 minutes. Observations were carried out at 
moderate airmass, with the bright Moon only 18 deg away, at a mean epoch 
of May 28.179 UT (13.94 hr after the GRB).

Inside the refined XRT error circle (Evans et al., GCN 14705; see also 
http://www.swift.ac.uk/xrt_positions/) we do not detect any bright 
source, but there is a faint, apparently extended object with magnitude 
z = 21.4 +- 0.2. The limiting magnitude for an isolated object in our 
coadded image is z = 22.1. Calibration has been derived using two stars 
in the USNO B1 catalog (0652-0853265 and 0652-0853288), and converting 
their R2 and I magnitudes into z using the transformation equations from 
Jordi et al. (2006, A&A, 460, 339). The source could be the GRB host.

A snapshot showing our coadded image can be found at the URL 
http://www.astro.ku.dk/~malesani/GRB/130527A/GRB130527A_finder_NOT.jpg