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)
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".]