TITLE:   GCN CIRCULAR
NUMBER:  7813
SUBJECT: GRB 080603B : Liverpool Telescope Observations
DATE:    08/06/04 17:13:50 GMT
FROM:    Andrea Melandri at Liverpool John Moores U  <axm@astro.livjm.ac.uk>

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


On 2008 Jun 03 at 21:32:57UT we observed the Swift GRB 080603B
(trigger=313087, Mangano et al., GCN 7794) with the Liverpool Telescope
using SDSS-I, SDDS-R and Bessell-B filters.

The OT reported by Rujopakarn et al. (GCN 7792), Mangano et al. (GCN
7794), Klotz et al. (GCN 7795, 7799), Castro-Tirado et al. (GCN 7796)
and Zhuchkov et al.(GCN 7803) is well detected in all our single 300s
exposures.

We calibrated the afterglow magnitude using B, R and I magnitudes of few
USNO B1 stars in the field of view.

Our observations started soon after the plateau phase reported by Klotz et
al. (GCN 7795) and Castro-Tirado et al. (GCN 7796) but our I-band and
R-band images were acquired before and after the optical break reported by
Zhuchkov et al.(GCN 7803).

We found alpha_I= 0.55 +/- 0.03 before the optical break and
alpha_R= 1.03 +/- 0.02 after the break, confirming the values found by
Zhuchkov et al.(GCN 7803).