TITLE:   GCN CIRCULAR
NUMBER:  5827
SUBJECT: GRB 061121: Faulkes Telescope North Optical Observation
DATE:    06/11/21 16:38:21 GMT
FROM:    Andrea Melandri at Liverpool John Moores U  <axm@astro.livjm.ac.uk>

A. Melandri (Liverpool JMU), C. Guidorzi (Univ Bicocca & INAF-OAB),
C.G. Mundell, I.A. Steele, R.J. Smith, A. Monfardini, D. Carter, 
S. Kobayashi, D. Bersier, M. Bode (Liverpool JMU), A. Gomboc 
(University of Ljubljana),  P. O'Brien, E. Rol, N. Bannister (Leicester) 
report:


The 2-m Faulkes North Telescope (Hawaii) automatically reacted to the 
Swift burst GRB061121 (trigger=239899, Page et al. GCN 5823). 

Observations started about 4.4 min after the trigger time. We confirm
the detection of the optical counterpart at the position

RA(J2000)  =  09:48:54.58
Dec(J2000) = -13:11:42.8

0.6" uncertainty, coincident with the UVOT and ROTSE counterpart 
(Yost et al. GCN 5824).

The automatic pipeline LT-TRAP identified a fading afterglow in BVRi' 
filters, and we estimate an initial magnitude R = 16.7 +/- 0.3 
(wrt USNOB) at t=4.4min.

The temporal decay index between 4 and 20 minutes after the burst
is alpha = 1.0 +/- 0.1.

Further observations and analysis are ongoing.

[GCN OPS NOTE(21nov06): Per author's reuqest, the error value on alpha
was changed from 1.0 +/- 1.0" to "1.0 +/- 0.1".]