TITLE:   GCN CIRCULAR
NUMBER:  6018
SUBJECT: GRB 050904: Second Epoch of HST/NICMOS Observations
DATE:    07/01/17 19:41:48 GMT
FROM:    Edo Berger at Carnegie Obs  <eberger@ociw.edu>

E. Berger (Carnegie Observatories) reports on behalf of a large 
collaboration:

"We re-observed the position of GRB 050904 (z=6.295) with NICMOS on the 
Hubble Space Telescope on 2006 July 22 UT.  A total of 6 orbits (15360 
sec) were obtained with the F160W (H-band) filter.  Previous observations 
of the burst with NICMOS on 2005 Sep 27 UT revealed a source with 
F160W(AB)=26.1+/-0.2 mag (Berger et al. astro-ph/0603689), which was 
interpreted as a combination of afterglow and host galaxy light.  The new 
observations reveal no source at the position of the burst to a 3-sigma 
limit of F160W(AB)=27.2 mag.  This result indicates that the host galaxy 
is fainter than about 0.05 microJy, and that the light contribution from 
the afterglow to the source detected in the Sep 2005 observations was
>60%, confirming the proposed jet break at t~3 days (Tagliaferri et al. 
2005; Haislip et al. 2006).

A complete analysis of the new NICMOS observations, and their implications 
for the afterglow and host galaxy properties, will be made available in a 
revised version of astro-ph/0603689."