GCN Circular 9482

D. Xu, G. Leloudas, D. Malesani, J. P. U. Fynbo, J. Maund (DARK/NBI), P. 
Jakobsson (Univ. Iceland), and T. Liimets (NOT & Tartu Obs.) report on 
behalf of a larger collaboration:

We continued to observe the field of GRB 090529 (Sakamoto et al., GCN 
9430
Not found
 
 
) with the Nordic Optical Telescope equipped with ALFOSC.  We 
obtained 3x600 s R-band frames staring on June 01, 21:26:31 UT and 
ending on June 01, 22:00:52 UT. The mid-exposure time is 3.31 days after 
the burst.

The optical afterglow (Xin et al., GCN 9431
Not found
 
 
; Schady et al., GCN 9435
Not found
 
 
) is 
still detected in the stacked frame. Using the same reference star as in 
  Kann et al. (GCN 9436
Not found
 
 
) and in Leloudas et al. (GCN 9453
Not found
 
 
), we obtain 
R=22.8+/-0.1 for the afterglow.

Measurements by Kann et al. (0.3 day after the burst) and Leloudas et 
al. (1.29 days after the burst) indicate an optical power-law decay 
index of alpha1=0.72. Our new observation indicates that the optical 
decay became even slower, with an index of alpha2=0.3 between our two 
obs epochs. In contrast, during the whole period of 0.3 - 3.31 days the 
X-ray afterglow decays with the index of ~1.0 (ref, Evans et al. 2009). 
The slow optical decay may be also due to the presence of a fairly 
bright host galaxy.

Further optical observations are encouraged.