GCN Circular 45917
Subject
GRB 261011A : MITSuME Akeno optical afterglow candidate detection
Event
Date
2026-10-12T03:31:32Z (2 days ago)
From
Ichiro Takahashi at Science Tokyo <itakahashi@hp.phys.titech.ac.jp>
Via
Web form
I. Takahashi, M. Sasada, H. Hagio, Y. Kubo, A. Ochi, R. Kato, N. Hosoya, J. Yonamine, Y. Yatsu, N. Kawai (Science Tokyo), and M. Niwano (NAOJ) report on behalf of the MITSuME collaboration:
We observed the field of GRB 261011A detected by Swift (Cenko et al., GCN 45896) and SVOM (Huang et al., GCN 45895) with the optical three-color (g', Rc, and Ic) CCD cameras mounted on the MITSuME 50-cm telescope Akeno.
The observations started at 2026-10-11 13:50:44 UT (243 s after the Swift/BAT trigger). We stacked the images obtained under good observing conditions. We detected an optical afterglow candidate at the position reported by Swift-UVOT (Cenko et al., GCN 45896).
The preliminary photometry of the source is as follows:
T0+[sec] | MID-UT | T-EXP[sec] | Magnitudes
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580 | 2026-10-11 13:56:21 | 260 | Rc=16.5+/-0.1, Ic=16.2+/-0.1
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T0+ : Elapsed time after the Swift/BAT 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).