GCN Circular 17788

K. L. Murata (Nagoya U.), S. Nishiyama, A. Iwamatsu, I. Kawamata (Miyagi
University of Education), and T. Nagayama (Kagoshima U.)

We observed the field of GRB 150428B ( Page et al., GCN Circular #17766) with
the near-infrared (J, H, Ks) simultaneous imaging camera SIRIUS attached to 1.4
m telescope IRSF ( InfraRed Survey Facility) in Sutherland observatory, South
Africa.

The observations started on 2015-04-28 03:59:59 UT (~ 48 min. after the burst).
We could not detect the afterglow within the XRT error circle reported in the
GCN circular in the three bands.
We have obtained the following preliminary upper limits (Vega magnitude system):
 J  > 17.4
 H  > 16.8
 Ks > 15.3.

Given magnitudes were calibrated against 2MASS point sources in this field.
The upper limits were determined as the magnitudes of the faintest star within 1
arcmin from the XRT position.

This observation was carried out by IRSF and OISTER collaboration.