GCN Circular 22660
Subject
GRB 180418A: NOT optical observations
Date
2018-04-19T00:20:53Z (6 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
Daniele Malesani (DAWN/NBI and DARK/NBI), Kasper Elm Heintz (Univ.
Iceland and DAWN/NBI), Maria Stone (Univ. Turku), and James Stone,
report on behalf of a larger collaboration:
We observed the optical afterglow (Zheng & Filippenko, GCN 22647;
Guidorzi et al., GCN 22648; Troja et al., GCN 22652; Fong et al., GCN
22659) of GRB 180418A (D'Elia et al., GCN 22646) with the 2.5-m Nordic
Optical Telescope (NOT) equipped with StanCam.
Observations were carried out in the Bessel R filter, but calibrated
against SDSS r-band Pan-STARRS local photometry. A low S/N source is
detected at a position consistent with previous reports.
At a mid time of April 18.936 UT (15.72 hr after the trigger), we
measure for the counterpart r = 22.70 +- 0.15 AB.
Compared to the Gemini-North measurement (Fong et al., GCN 22659), we
infer a decay slope alpha = 0.75 +- 0.17, assuming F(t) propto t^-alpha.