[vsnet-grb-info 26293] GRB 200907B: MITSuME Okayama optical upper limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28393
SUBJECT: GRB 200907B: MITSuME Okayama optical upper limits
DATE:    20/09/08 01:35:11 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa at hp.phys.titech.ac.jp>

R. Hosokawa, K. L. Murata, R. Adachi, M. Niwano, F. Ogawa, N.
Nakamura, N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N.
Kawai (TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 200907B (Beardmore et al., GCN 28384;
Evans et al., GCN 28385,28391) with the optical three color (g', Rc, and Ic)
CCD cameras attached to the MITSuME 50 cm telescope of Okayama
Astrophysical Observatory, Okayama, Japan.

The observation with a series of 60 sec exposures started at
2020-09−07 18:52:16UT. We did not find any new point sources within
the enhanced Swift/XRT error circle (Evans et al., GCN 28391) in the
60 sec exposure images and the stacked images. We obtained the 5-sigma
limits of the stacked images as follows.

T0+[sec] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
65 2020-09-07T19:19:48 2100 g'>17.1, Rc>17.9, Ic>17.3
------------------------------------------------------------------------------------------------
T0+: Elapsed time after the burst
T-EXP: Total Exposure time

We used the PS1 catalog for flux calibration. The magnitudes are
expressed in the AB system. The images were processed in real-time
through the MITSuME GPU reduction pipeline (Niwano et al., accepted
for publication in PASJ, https://arxiv.org/abs/2008.11486;
https://github.com/MNiwano/Eclaire).