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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.
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