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GCN Circular 23195

Subject
GRB 180904A: NOT optical observations, candidate host galaxy
Date
2018-09-04T23:04:27Z (5 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), Sune Dyrbye (NOT), report on behalf of a largert 
collaboration:

We observed the field of GRB 180904A (D'Ai' et al., GCN 23194) with the 
Nordic Optical Telescope (NOT) equipped with the AlFOSC camera.

In an image of 300 s exposure taken with the SDSS r filter and 
commencing on Sep 4.9057 UT (15.6 min after the GRB), we detect a single 
object consistent with the currently available XRT position 
(http://www.swift.ac.uk/xrt_positions/). Its coordinates are (J2000):

RA = 18:16:59.74
Dec = +46:37:47.1

Compared to nearby stars from the Pan-STARRS survey, we measure for this 
object a magnitude r = 22.56 +- 0.08 AB.

We note that the same object is visible in the archival Pan-STARRS image 
of this field, with a measured magnitude r = 22.84 +- 0.15 AB. There is 
thus only marginal indication of excess flux in the NOT image. If this 
object is related to GRB 180904A, as suggested by the spatial 
coincidence with the X-ray position, it is largely or entirely dominated 
by the host galaxy.

Further observations are planned.
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