GCN Circular 18113

K. L. Murata (Nagoya U.), T. Kusune (Nagoya City U.), H. Onozato (Tohoku U.) and T. Nagayama (Kagoshima U.)

We observed the field of GRB 150727A (Cenko et al., GCN Circular #18076) with the near-infrared (J, H, Ks) simultaneous imaging polarimeter SIRPOL attached to 1.4 m telescope IRSF (InfraRed Survey Facility) in Sutherland observatory, South Africa.

The observations started on 2015-07-27 19:25:30 UT (~ 9 min. after the burst).
We detected an uncatalogued source within 5 arcsec from the Swift/UVOT preliminary position reported in the GCN circular of Breeveld et al. (GCN Circular #18084).
We have obtained the following preliminary magnitude (Vega magnitude system):

J   = 18.9 +- 0.2
H   = 18.1 +- 0.1
Ks  = 17.1 +- 0.2

Given magnitudes were calibrated against 2MASS point sources in this field.

This observation was carried out by IRSF and OISTER collaboration.