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GCN Circular 36227

GRB 240419B : MITSuME Akeno optical upper limits
2024-04-22T11:00:03Z (3 months ago)
Narikazu Higuchi at Tokyo Tech <>
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N. Higuchi, Y. Kubo, S. Joshima, H. Hagio, I. Takahashi, M. Sasada, M. Niwano, S. Hayatsu, H. Seki, Y. Yatsu and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 240419B (Dichiara et al., GCN 36180) with the optical three-color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50-cm telescope Akeno. 

The observation started at 2024-04-19 17:46:23 UT (5.4 hrs after the Swift/BAT trigger). We stacked the images with good conditions. We did not detect any uncatalogued sources within the enhanced Swift/XRT error region (Osborne et al., GCN 36186), despite the detection report of Daniele et al., (GCN 36191). We obtained the 5-sigma limits of the stacked images as follows.

T0+[hrs] | MID-UT | T-EXP[sec] | 5-sigma limits
6.4 | 2024-04-19 18:44:10.13 | 3660 | g'>18.6, Rc>18.8, Ic>18.4
T0+ : Elapsed time after the trigger
T-EXP: Total Exposure time

We used the PS1 catalog for flux calibration. The catalog magnitudes in PS1 g, r and i bands were converted to our g', 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;
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