GCN Circular 22000
D. Malesani (DARK/NBI), K. E. Heintz (Univ. Iceland and DARK/NBI), P. Calissendorff (Stockholm Univ), and I. R. Losada (NOT) report on behalf of a larger collaboration: We observed the optical counterpart (Thorstensen & Halpern, GCN 21987; Izzo & Malesani, GCN 21988; Guidorzi et al., GCN 21991) of the Fermi GRB 171010A (Poolakkil & Meegan, GCN 21992; Omodei et al., GCN 21985) with the Nordic Optical Telescope equipped with the StanCam imager. Observations were carried out in the Johnson-Cousins BVRI filters. The optical counterpart is well detected in our images. Using the Pan-STARRS catalog as reference, we measure a magnitude r = 19.18 +- 0.06 AB at an epoch Oct 12.03 UT (29.74 hr after the trigger). Comparing our measurement with the report by Thorstensen & Halpern (GCN 21987) we infer a decay index alpha = 1.4 assuming an unbroken power-law decay.