TITLE:   GCN CIRCULAR
NUMBER:  27271
SUBJECT: GRB 200228B: Liverpool Telescope imaging
DATE:    20/02/29 13:57:42 GMT
FROM:    Daniel Perley at Liverpool JMU  <d.a.perley@ljmu.ac.uk>

D. A. Perley and A. M. Cockeram (LJMU) report:

On 2020-02-29 UT we obtained imaging of the position of GRB 200228B 
(Fermi GBM team, GCN 27253; Laha et al., GCN 27254) using the 2m robotic 
Liverpool Telescope.  We collected 3x120s of exposure time in each of 
the the i-band and z-band filters, beginning at 05:53:44 and ending at 
06:07:33 (UTC).

No unambiguous source is detected in either stacked image, although a 
possible marginal (~3-sigma) source is present close to the center of 
the latest enhanced XRT error circle in the z-band image.  Photometry of 
this potential source (calibrating relative to PS1 catalog stars in the 
field) gives an approximate magnitude of z = 21.7 +/- 0.3.

3-sigma limits are:

dt(days)  filter   mag
0.7794    i       >22.6
0.7844    z       >21.7

We additionally note that Pan-STARRS1 imaging of the field shows several 
faint, probably-resolved sources close to the survey detection limit 
inside or closely outside the XRT error circle, which could represent a 
possible host galaxy or host group.

Imaging of the field is available at:
http://www.astro.ljmu.ac.uk/~aridperl/grb/200228b/GRB200228B_LT_PS1.png

(The enhanced XRT error circle is shown in cyan with the marginal 
"detection" highlighted in red.)










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