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GCN Circular 32883

GRB 221028A: MITSuME Okayama optical upper limits
2022-10-29T07:02:15Z (a year ago)
Masafumi Niwano at Tokyo Institute of Tech <>
M. Niwano, R. Hosokawa, I.Takahashi, K. L. Murata, Y. Imai, N. Ito, S. 
Sato, N. Higuchi, M. Tateda, M. Sasada, Y. Yatsu, and N. Kawai (Tokyo 
Tech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 221028A (A. Y. Lien et al. GCN Circular 
#32874, H. Kumar et al. GCN Circular #32876, Y.-D. Hu et al. GCN 
Circular #32878, V. Lipunov et al. GCN Circular #32879, R. Strausbaugh 
et al. GCN Circular #32881) with the optical three color (g', Rc, and 
Ic) CCD cameras attached to the MITSuME 50 cm telescope Okayama.

The observation with a series of 60 sec exposures started at 2022-10-28 
13:17:23 UT (59 seconds after the Swift/BAT trigger). We stacked the 
images with good conditions. We did not detect any uncatalogued sources 
within the Swift/XRT error region (A. Y. Lien et al. GCN Circular 
#32874). We obtained the 5-sigma limits of the stacked images as follows.

T0+[sec] | MID-UT | T-EXP[sec] | 5-sigma limits
59 | 2022-10-28 14:17:10 | 5790.0 | g'>18.7, Rc>19.5, Ic>18.7
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;
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