TITLE:   GCN CIRCULAR
NUMBER:  24328
SUBJECT: LIGO/Virgo S190425z : IRSF/SIRIUS NIR photometric follow-up observation of the Swift/UVOT Transient
DATE:    19/04/28 13:15:44 GMT
FROM:    Kumiko Morihana at Nagoya University  <morihana@u.phys.nagoya-u.ac.jp>

K. Morihana (Nagoya U.), M. Jian (U. of Tokyo), T. Nagayama (Kagoshima
U.) on behalf of J-GEM collaboration

We carried out NIR photometric follow-up observation of Swift/UVOT
transient (Breeveld et al.,GCN 24296) of the GW event S190425z (GCN
24168) with the near-infrared (J, H, Ks) simultaneous imaging camera
SIRIUS attached to the IRSF (InfraRed Survey Facility) 1.4 m telescope
in Sutherland Observatory, South Africa.

The observation started on 2019-04-28 00:44:28 UT. The exposure time
on the source is 40 min. A very faint source (possibly noise) is seen
at the position of Swift/UVOT transient in the J-band image. The
simple aperture photometry returns J=20.2 mag (Vega system), but it is
quite unsure. The conservative upper limit magnitudes for the
JHKs-band images are 18.8 mag, 18.4 mag, and 16.9 mag (Vega system),
respectively.