GCN Circular 36113

N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), S. Belkin (IKI) report on behalf of GRB-IKI-FuN:

We observed the field of GRB 240414A (Caputo et. al., GCN 36083
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) at redshift z=1.833 (Adami et al., GCN 36085
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; de Ugarte Postigo et al., GCN 36087
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) with 1.5-meter AZT-33IK telescope of Sayan observatory at Mondy. The observations were started on 2024-04-14 (UT) 13:56:41, i.e. ~12 hr since the Swift trigger. We took 45 frame 120 s each in the R-filter.
The optical counterpart (Schneider et al., GCN 36084
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; Adami et al., GCN 36085
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; de Ugarte Postigo et al., GCN 36087
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; Niwano et al., GCN 36088
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; Lipunov et al., GCN 36095
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; Dutton et al., GCN 36097
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; Peretto, GCN 36100
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; Turpin et al., GCN 36101
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; Karambelkar et al., GCN 36103
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) is well detected in the stacked image at coordinates of (J2000) 12:19:08.09 +56:44:28.8. Preliminary photometry of the optical source is following:

Date       UT_start  t-T0     Filter Exp.  OT    err  UL(3sigma)
                    (mid, days)     (s)
2024-04-14 13:56:41  0.51395  R     44*120 20.60 0.12 22.2

The magnitudes were calibrated with respect to nearby USNO-B1.0 stars.
Assuming no spectral evolution between earlier observations(Turpin et al., GCN 36101
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),  we  estimate a power law decay index to be alpha~1.2, which is in agreement with SkyNet observations (Dutton et al., GCN 36097
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).