[AAVSO-HEN] GRB 090812: Liverpool Telescope afterglow confirmation

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  9770
SUBJECT: GRB 090812: Liverpool Telescope afterglow confirmation
DATE:    09/08/12 07:19:41 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi at fe.infn.it>

R.J. Smith (Liverpool JMU), A. Gomboc (U. Ljubljana), C. Guidorzi (U. 
Ferrara),
C.G. Mundell, I.A. Steele, A. Melandri, S. Kobayashi, C.J. Mottram, D.F. 
Bersier,
Z. Cano (Liverpool JMU) report on behalf of a large collaboration:

On 2009 August 12 at 06:03:54 UT the 2-m Liverpool Telescope automatically
began observing the Swift GRB 090812 (Stamatikos et al., GCN Circ. 9768)
using the r' and i' filters.

We clearly detected the fading optical afterglow reported by Swift-UVOT
and P60 (Cenko et al. GCN Circ. 9769) with the following values:

Mid Time   Delay from BAT   Total Exp  Filter     Mag
(UT)       trigger (s)      (s)
----------------------------------------------------------
06:03:59    111             10         r'    15.51 +- 0.04
06:06:26    258             10         r'    16.60 +- 0.10
----------------------------------------------------------

Magnitudes have been calibrated from nearby SDSS stars.