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GCN Circular 30855

Subject
GRB 210919A: MITSuME Akeno optical upper limits
Date
2021-09-20T00:36:51Z (3 years ago)
From
Yutaka Takamatsu at Tokyotech <takamatsu@hp.phys.titech.ac.jp>
Y. Takamatsu, R. Hosokawa, K. L. Murata, N. Ito, Y. Imai, M. Niwano,
R. Noto, S. Sato, M. Takaku, R. Yamaguchi, Y. Yatsu, and N. Kawai
(TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210919A (A. Tohuvavohu et al. GCN
Circular #30846, V. Lipunov et al. GCN Circular #30847, Y.-D. Hu et
al. GCN Circular #30848, R. Strausbaugh et al. GCN Circular #30849,
M.R. Goad et al. GCN Circular #30850, N. Pankov et al. GCN Circular
#30851, D. A. Perley et al. GCN Circular #30852, M. Perri et al. GCN
Circular #30854) with the optical three color (g', Rc, and Ic) CCD
cameras attached to the MITSuME 50 cm telescope Akeno. The observation
with a series of 60 sec exposures started at 2021-09-19 15:22:32 UT
(14.9 hours after Swift trigger). We stacked the images with good
conditions. We did not detect any uncatalogued sources within the XRT
error region (M.R. Goad et al. GCN Circular #30850). We obtained the
5-sigma limits of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
17.3 2021-09-19 17:48:08.43 11160 g'>19.2, Rc>20.5, Ic>19.6
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time

We used 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).
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