GCN Circular 22535
Subject
GRB 180325A: NOT redshift
Date
2018-03-25T03:33:36Z (6 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
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.