TITLE: GCN CIRCULAR NUMBER: 9687 SUBJECT: GRB 090715B: further NOT optical observations DATE: 09/07/18 15:31:46 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst D. Malesani (DARK/NBI), G. C. Cox (NOT), C. Mackay, D. King, T. Staley (IoA Cambridge), and P. Jakobsson (Univ. Iceland) report on behalf of a larger collaboration: We observed again the field of GRB 090715B (Vetere et al., GCN 9668) using the NOT telescope equipped with the StanCam instrument. The optical afterglow (Vetere et al., GCN 9668; Smith et al., GCN 9670) is well detected in the V and R filters, and is still bright. Using the same reference star as in GCN 9671, we measure R ~ 21.3 on mean time July 17.94 UT (2.06 days after the GRB). Assuming an unbroken power-law fading (Fnu propto t^-alpha), the corresponding decay index is alpha ~ 0.44, which is unusually flat at such late epoch (although not unprecedented). Our measurement is also consistent within the uncertainties with the broken power-law fit reported by Guidorzi et al. (GCN 9677). DM thanks Carole G. Mundell and Cristiano Guidorzi for discussion.