GCN Circular 35099

I. Andreoni (JSI/UMD/NASA-GSFC), G. Srinivasaragavan (UMD), B. O'Connor (CMU), T. Ahumada (Caltech), S. B. Cenko (NASA-GSFC), J. Durbak (UMD), E. Hammerstein (UMD), N. Klingler (UMBC/NASA-GSFC), A. Kutyrev (NASA-GSFC), L. Singer (NASA-GSFC), S. Veilleux (UMD):

We report target of opportunity follow-up observations of GRB 231117A (Laha et al., GCN 35071
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; Navaneeth et al., GCN 35072
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; Beardmore et al., GCN3574
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; Cattaneo et al., GCN 35075
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; Svinkin et al., GCN 35079
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; Cheung et al., GCN 35081
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, Dafcikova et al., GCN 53095
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) with the Large Monolithic Imager (LMI) mounted at the Lowell Discovery Telescope (LDT) located in Flagstaff, AZ, under program M01 (PI: Andreoni).

Observations started on 2023-11-18 at 01:46 UT (~22.7 hr after the GRB trigger). We obtained sets of 4x150s exposures for each g-r-i-z filter. The candidate afterglow identified by Yang et al.; GCN 35083
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 (also detected by Rastinejad et al., GCN 35087
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; Gompertz et al., GCN 35088
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; Kumar et al., GCN 35089
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, Ahumada et al., GCN 35093
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; Rhodes et al., GCN 35097
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) is well detected. Preliminary photometry of the images, with contribution from the host galaxy included and not corrected for Galactic extinction, was measured as follows in the AB magnitude system:

g = 20.55 +/- 0.04 mag
r = 20.20 +/- 0.04 mag
i = 20.05 +/- 0.04 mag
z = 19.98 +/- 0.03 mag

We thank Ben Shafransky and the Lowell Observatory staff for their support.