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GCN Circular 34268

GRB 230723B: MITSuME Akeno optical afterglow candidate detection
2023-07-26T13:34:48Z (10 months ago)
Mahito Sasada at Tokyo Institute of Technology <>
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M. Sasada, I. Takahashi, M. Niwano, S. Sato, S. Hayatsu, N. Higuchi, H. Takei, H. Seki, Y. Yatsu (Tokyo Tech), K. L. Murata (Kyoto U) and N. Kawai (Riken) report on behalf of the MITSuME collaboration:

We observed the field of GRB 230723B (Page et al. GCN Circular #34234, Campana et al. #34236, Page et al. #34238, Lipunov et al. #34239, Siegle et al. #34240, Agui Fernandez et al. #34241, Adami et al. #34247, Osborne et al. #34248, Mangan et al. #34249, Quadri et al. #34250, Agui Fernandez et al. #34251, Leonini et al. #34252, Ruocco et al. #34253, Pavoni et al. #34254, Lopresti et al. #34259, Anderson et al. #34267) 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 10 sec exposures started at 2023-07-23 11:43:20 UT (48 seconds after the Swift/BAT detection). We stacked the images with good conditions. In the stacked image at 454 seconds after the burst, we detected an object of Ic=17.1+/-0.2 at the coordinate reported by Agui Fernandez et al. #34251. We also report the g’-, Rc- and Ic-band 3-sigma upper limits of the stacked images.

T0+[sec] |MID-UT | T-EXP[sec] | 3-sigma limits
454  | 2023-07-23 11:50:06 | 220 | g’>18.0, Rc>17.8, Ic>17.6
1419 | 2023-07-23 12:06:11 | 1020 | g’>18.6, Rc>18.5, Ic>18.2
 3763 | 2023-07-23 12:45:15 | 1890 | g'>19.0, Rc>18.5, Ic>18.0
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time

We used the PS1 catalog for flux calibration. The catalog magnitudes in PS1 r and i bands were converted to our Rc- and Ic-band magnitudes following Tonry et al. (2012), Table 6. 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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