[vsnet-grb-info 27393] GRB 210212A: MITSuME Akeno optical upper limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29496
SUBJECT: GRB 210212A: MITSuME Akeno optical upper limits
DATE:    21/02/12 16:58:03 GMT
FROM:    Katsuhiro L. Murata at Nagoya U  <murata at u.phys.nagoya-u.ac.jp>

K. L. Murata, R. Adachi, R. Hosokawa, 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 210212A (Troja et al. GCN #29487, Beardmore et
al. GCN #29489, Palmer et al. GCN #29491, Kuin et al. GCN #29492, Hu et al.
GCN #29494, Tohuvavohu et al. GCN #29495)  with the optical three color
(g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of
Akeno Observatory, Yamanashi, Japan. The observation with a series of 60
sec exposures started at 2021-02-12 08:51:45 UT(4.43 hours after the Swift
BAT trigger). We stacked the images with good conditions. We did not find
any new point sources within the enhanced Swift XRT circle (Beardmore et
al. GCN #29489) in all three bands.
We obtained the 5-sigma limits of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
8.6 13:05:08 5400 g'>18.6, Rc>18.5, Ic>17.8
------------------------------------------------------------------------------------------------
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. 2021, PASJ, Vol.73, Issue 1,
Pages 4-24; https://github.com/MNiwano/Eclaire).