TITLE:   GCN CIRCULAR
NUMBER:  12346
SUBJECT: GRB 110915A: Deep Gemini-South i/z-band imaging
DATE:    11/09/16 04:40:32 GMT
FROM:    Daniel Perley at U.C. Berkeley  <dperley@astro.berkeley.edu>

D. A. Perley (Caltech), A. Cucchiara (UC Santa Cruz), and N. R. Tanvir
(Leicester) report on behalf of a larger collaboration:

We imaged the field of GRB 110915A (Holland et al., GCN 12335) with 
GMOS-S on Gemini-South starting at 00:36 UT on 2011-09-16.  We acquired 
6x240 seconds in i-band, and 7x240 seconds in z-band. Conditions were 
clear with generally good seeing (0.7").

We find no significant sources within the XRT error circle in either 
filter.  We calculate the following 3-sigma limits:

   i > 26.0 mag  (t_mid = 11.49 hr)
   z > 24.9 mag  (t_mid = 12.03 hr)

Given the bright X-ray afterglow and and other optical limits reported 
to date, these results indicate that GRB 110915A is a very dark burst, 
as also noted by Malesani et al (GCN 12343).  Infrared and radio 
follow-up is encouraged.