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GCN Circular 34268

Subject
GRB 230723B: MITSuME Akeno optical afterglow candidate detection
Date
2023-07-26T13:34:48Z (10 months ago)
From
Mahito Sasada at Tokyo Institute of Technology <sasada@hp.phys.titech.ac.jp>
Via
Web form
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; https://github.com/MNiwano/Eclaire).
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