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GCN Circular 35119

Subject
GRB 231117A: MAAO 0.7-m telescope optical upper limit
Date
2023-11-19T07:32:15Z (3 months ago)
From
Gu Lim at Pusan National University <lim9gu@gmail.com>
Via
Web form
Lim, Gu (PNU); Park, Junyeong (PNU); Kim, Dohyeong (PNU); Paek, Gregory S. H. (SNU); Im, Myungshin (SNU); Park, Keunhong (MAAO); Choi, Changmin (MAAO); and GECKO Collaboration

We searched for the optical afterglow of GRB 231117A (S. Laha et al., GCN 35071) with a 0.7m telescope at Miryang Arirang Astronomical Observatory (MAAO), one of the facilities of the GW EM-Counterpart Korean Observatory (GECKO). We started the observation at 2023-11-17 10:04:30 UT and obtained 30 images of each 120s with I-band after 6.9 hours after the Swift detection (GCN 35071). No significant source is found within the updated Swift-XRT position (Beardmore et al. GCN 35074). The photometry is performed using a 2xFWHM diameter aperture. The flux is calibrated using the PanStarrs DR1 photometric catalog (AB system) as a reference. The depth is the limiting magnitude for a point source without the galactic extinction correction.

T0 = 2023-11-17T03:03:19 UT (Laha et al., GCN 35071)
Filter Mean_Date-obs(UT)    exptime(s)   T-T0(d)        FWHM(")    Depth_3sigma(AB)   Depth_5sigma(AB) zp       zper
--------------------------------------------------------------------------------------------------------------------------------------------------
I          2023-11-17T10:38:14  120x30           +0.32             3.41              >20.34                           >19.78                         25.99  0.02

Our detection limit is deeper than the report from MITSuME (Takei et al., GCN 35076).

Gravitational-wave EM Counterpart Korean Observatory (GECKO) is a network of 10+ 0.4m to 1m class telescopes worldwide.
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