[vsnet-grb-info 22215] LIGO/Virgo S190425z: Liverpool Telescope imaging of ZTF19aasckkq

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24314
SUBJECT: LIGO/Virgo S190425z: Liverpool Telescope imaging of ZTF19aasckkq
DATE:    19/04/28 00:46:18 GMT
FROM:    Daniel Perley at Liverpool JMU  <d.a.perley at ljmu.ac.uk>

D. A. Perley, C. M. Copperwheat, and K. L. Taggart (LJMU) report on 
behalf of the Global Relay of Observatories Watching Transients Happen 
(GROWTH) collaboration:

We acquired a series of 60-second exposures of ZTF19aasckkq (Anand et 
al., GCN 24311), an optical transient in the error region of LIGO/Virgo 
S190425z (GCN 24168), using the IO:O imager on the 2m Liverpool 
Telescope in the u, g, r, i, and z filters between 03:17:56 and 03:30:00 
UT on 2019-04-27.

The transient is detected with the following magnitudes (measured after 
image subtraction and calibrated relative to PS1):

JD          	magnitude
2458600.6384	g = 20.66 +/- 0.18
2458600.6395	r = 20.37 +/- 0.17
2458600.6406	i = 20.28 +/- 0.23
2458600.6416	z = 20.09 +/- 0.38

It is not detected in u-band.  These suggest a moderately but not 
extremely red transient and show no obvious evolution relative to the 
ZTF imaging on 2019-04-26 (g = 20.86 +/- 0.18).













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