TITLE: GCN CIRCULAR NUMBER: 9488 SUBJECT: GRB 090530: Further NOT optical observations DATE: 09/06/03 19:51:39 GMT FROM: Dong Xu at DARK,NBI D. Xu, G. Leloudas, D. Malesani, J. P. U. Fynbo, J. Hjorth (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 090530 (Cannizzo et al., GCN 9438) with the Nordic Optical Telescope equipped with ALFOSC. We obtained 3x600 s R-band frames staring on June 01, 22:04:19 UT, 66.7669 hr after the burst. The optical afterglow (Cannizzo et al., GCN 9438) is still detected in the stacked frame. The magnitude is R=22.6+/-0.2 against the same reference star in Malesani et al. (GCN 9452). Balman et al. (GCN 9487) found a 3sigma upper limit of R=21.1+/-0.5 mag at 15.2 hr after the burst. Our first observation shows R=21.6 mag at 17.8 hr after the burst. Rossi et al. (GCN 9458) found R=22.2+/-0.2 mag at 21.3 hr after the burst, and a break in the light curve at around 22 ksec post-burst with slopes of 0.5+-0.1 (pre-break) and 1.8+-0.4 (post-break), using previous obs (Flewelling et al., GCN 9439; Schady et al., GCN 9450; Nissinen & Hentunen, GCN 9442). Our new observation indicates that the optical decay is becoming much slower. The slower optical decay may be due to the presence of a fairly bright host galaxy. Further optical observations are encouraged.