[vsnet-grb-info 7118] GRB 081222: Faulkes Telescope South observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8699
SUBJECT: GRB 081222: Faulkes Telescope South observations
DATE:    08/12/22 13:51:17 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi at fe.infn.it>

A. Melandri (Liverpool JMU), C. Guidorzi (U. Ferrara), D. Carter 
(Liverpool JMU)
report on behalf of a larger collaboration:

On 2008 December 22 (10:17:46 UT) we began observing the field of GRB 081222
(Grupe et al. GCN Circ. 8691) with the Faulkes Telescope South.
Observations consisted of two sequences of 6x300s exposures acquired
using the SDSS-i and SDSS-r filters, respectively.

We clearly detect the optical afterglow reported by REM (Covino et al.
GCN Circ. 8692) and GROND (Updike et al. GCN Circ. 8693), with the following
magnitudes:

Telescope   Filter  T_mid[hr]   Exposure[s]      Mag
--------------------------------------------------------------
FTS          SDSS-i    5.47        2x300        20.45 +/- 0.25
FTS          SDSS-r    6.01        2x300        21.34 +/- 0.30
--------------------------------------------------------------

The calibration was performed using the R2 and I magnitudes of several
USNOB-1 catalogue field objects. Uncertainties include the different
zero points of the USNOB-1 stars. Compared with the value reported by GROND
(Updike et al. GCN Circ. 8693), we estimate a power-law index between the
two epochs of about 1.1 .