TITLE:   GCN CIRCULAR
NUMBER:  24319
SUBJECT: LIGO/Virgo S190425z: NOT photometry of ZTF19aasckkq
DATE:    19/04/28 04:18:11 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani@dark-cosmology.dk>

L. Izzo (HETH/IAA-CSIC), D. B. Malesani (DAWN/NBI and DARK/NBI), R. 
Carini (INAF/OAR) report:

We observed the field of ZTF19aasckkq, reported by the Zwicky Transient 
Facility (Anand et al., GCN 24311) to lie within the localization area 
of the LIGO/Virgo trigger S190425z (GCN 24168). We used the Nordic 
Optical Telescope (NOT) located in La Palma (Canary Islands, Spain) and 
equipped with the AlFOSC camera.

We report the following magnitudes on the approximate date April 28.14 
UT (2.8 days after the explosion of S190425z):

g = 20.63 +- 0.02
r = 20.33 +- 0.02
i = 20.29 +- 0.02

These magnitudes are calibrated against the Pan-STARRS survey; no 
subtraction of the host galaxy was attempted, but the target is 
relatively isolated and host contamination should not be a major 
contribution. Our measurements are consistent with those reported by 
Anand et al. (GCN 24311) on April 26 (unspecified time), as well as by 
Perley et al. (GCN 24314) on April 27.14 UT.

The object seems therefore slowly variable, and less likely to be 
associated with S190425z.