GCN Circular 22535
K. E. Heintz (Univ. Iceland and DAWN/NBI), J. P. U. Fynbo (DAWN/NBI), D. Malesani (DAWN/NBI and DARK/NBI), report on behalf of a larger collaboration: We observed the optical counterpart of GRB 180325A (Troja et al., GCN 22532; Guidorzi et al., GCN 22534) with the 2.5-m Nordic Optical Telescope (NOT) equipped with ALFOSC, starting at 02:02:30 UT on 25 March 2018. We obtained 3x100 s in the r-band and measure a magnitude of m(r) = 18.61 +/- 0.03 mag at a mean post-explosion epoch of 11 minutes. The calibration was performed using local Pan-STARRS stars in the GRB field. This apparent magnitude is not corrected for foreground extinction. We subsequently obtained spectroscopy for a total of 3x600 s, using grism #4 and covering the wavelength range 3650-9450 AA. In our low-resolution spectrum we identify several absorption features, including Mg II, Fe II, Al II, C IV, Si II at a common redshift of z = 2.25. The 2175 AA bump is clearly visible at this redshift. We also note the presence of a strong intervening system at z = 2.04, as revealed by Mg II and Fe II absorption features. Further observations are in progress.