[vsnet-grb-info 17114] GRB 151021A: MITSuME Okayama Ks-band upper-limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18435
SUBJECT: GRB 151021A: MITSuME Okayama Ks-band upper-limit
DATE:    15/10/22 06:19:51 GMT
FROM:    Kenshi Yanagisawa at OAO/NAOJ  <yanagi at oao.nao.ac.jp>

K. Yanagisawa, D. Kuroda, Y. Shimizu, H. Izumiura(OAO/NAOJ),
M. Yoshida (Hiroshima), K. Ohta(Kyoto) and N. Kawai(Tokyo Tech.)
report on behalf of the MITSuME collaboration:

We observed the field of GRB 151021A (Melandri et al., GCN 18425)
in Ks-band with a wide-field near infrared imager at Okayama
Astrophysical Observatory (Japan).  The imager has effective
aperture of 0.91 m.

Observations started from 10:42 UT on 21th October, 9.2h after
the BAT trigger, to 11:11 UT. The total exposure of 11.7 min
was successfully obtained.

In our co-add image, we did not find any new point source within
the enhanced XRT error circle (Osborne et al., GCN 18428) down
to limiting magnitude of Ks=14.5 (Vega, S/N=10). The photometric
calibration was made against 2MASS field stars.

T0+[sec]    MID-UT     T-EXP[sec]      Ks
---------------------------------------------------
 +34,049    10:56      700.0           >14.5
---------------------------------------------------
T0+ : Elapsed time after the burt [sec]
T-EXP: Total Exposure time [sec]