[AAVSO-HEN] GRB090814A: NOT optical follow-ups

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TITLE:   GCN CIRCULAR
NUMBER:  9809
SUBJECT: GRB090814A: NOT optical follow-ups
DATE:    09/08/14 23:02:39 GMT
FROM:    Dong Xu at DARK,NBI  <dong at astro.ku.dk>

D. Xu, J.P.U. Fynbo (DARK/NBI), P. Jakobsson (Univ. Iceland), Tiina 
Liimets (NOT) report on behalf of a larger collaboration:

We observed the field of GRB 090814A (Ukwatta et al. GCN 9793; Updike et 
al., GCN 9794) with the Nordic Optical Telescope equipped with ALFOSC. 
We obtained 3x600 s R-band frames staring on August 14th,  21:15:11 UT, 
20.38 hr after the burst.

The optical afterglow is clearly detected in each frame. The magnitude 
is R~22.4 calibrated against the reference star, #1156-0231252 with 
R2=19.25,  of the USNO B1 catalog.

Compared with the previous measurement of R~21.5 around 70 mins after 
the burst (Jakobsson et al., GCN 9797), the afterglow is decaying quite 
shallowly, with a power-law slope of ~0.3, being consistent with the 
X-ray decaying law during the same period (Page & Ukwatta, GCN 9801).