TITLE:   GCN CIRCULAR
NUMBER:  38001
SUBJECT: GRB 241030B : MITSuME Akeno optical upper limits
DATE:    24/10/31 08:55:47 GMT
FROM:    hagio.h.ffca@m.isct.ac.jp

H. Hagio, Y. Kubo, N. Higuchi, I. Takahashi, M. Niwano, M. Sasada, S. Hayatsu, H. Seki, S. Joshima, Y. Yatsu and N. Kawai (Science Tokyo) report on behalf of the MITSuME collaboration:

We observed the field of GRB 241030B (Fermi GBM Team, GCN 37980, Klingler et al. GCN 37981) with the optical three-color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50-cm telescope Akeno. 

The observation started at 2024-10-30 18:44:33.72 UT (10.2 minutes 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(Evans et al. GCN 37992). We obtained the 5-sigma limits of the stacked images as follows.

T0+[min] | MID-UT | T-EXP[sec] | 5-sigma limits
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15.9 | 2024-10-30 18:50:13.75 | 480 | g'>18.7, Rc>18.6, Ic>18.1
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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; https://github.com/MNiwano/Eclaire).