[vsnet-grb-info 8428] GRB 090926B: optical object in error circle

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9944
SUBJECT: GRB 090926B: optical object in error circle
DATE:    09/09/27 07:45:32 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani at astro.ku.dk>

Daniele Malesani, Johan P. U. Fynbo (DARK/NBI) and V. D'Elia (ASDC and 
INAF/OAR) report on behalf of a larger collaboration:

We observed the field of GRB 090926B (Grupe et al., GCN 9935; Morii et 
al., GCN 9943) with the VLT UT1 equipped with FORS2. Seeing was 
0.8-0.9". Preliminary inspection of the image reveals a faint, slightly 
extended source at a position consistent with the revised XRT error 
circle (Grupe et al., GCN 9940; http://www.swift.ac.uk/xrt_positions). 
Its coordinates are (0.5" error):

RA(J2000) = 03:05:13.94
Dec(J2000) = -39:00:22.2

and its magnitude (based on archival zeropoints) is R ~ 23 on 2009 Sep 
27.246 UT (7.97 hr after the GRB). Inspection of the NOT images (Xu et 
al., GCN 9941) reveals a faint nebulosity, with a luminosity level 
consistent with the VLT measurement.

Presently, it is not clear whether this source is related to the GRB or 
not. It may be the host galaxy, or the blend of two faint, adjacent 
objects. Further observations are planned to evaluate its variability.

We gladly acknowledge excellent support from the ESO observing staff 
during a busy night, in particular Yuri Beletsky, and Stephane Brillant.