TITLE: GCN CIRCULAR NUMBER: 38580 SUBJECT: GRB 241215A: Mondy AZT-33IK optical observations DATE: 24/12/16 12:34:55 GMT FROM: Nicolai Pankov at HSE, IKI RAS colinsergesen@gmail.com

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

We performed optical observations of the field of GRB 241215A (Mereghetti et. al, GCN 38573; Mohan et. al, GCN 38574; Leonini et. al, GCN 38575; Liu et. al, GCN 38576) in the R filter with AZT-33IK of Sayan (Mondy) observatory. The observations began on 2024-12-15 14:27 UT, i.e. ~1.08 hr since INTEGRAL trigger. We have covered the entire localization area assessed by the INTEGRAL team (Mereghetti et. al, GCN 38573). No candidate transients were found using image subtraction with ```apex_subtract``` pipeline against the PS1 template image. The preliminary upper limit of the stacked image is given below:

| Date | UTstart | t-T0 (mid, days) | Exptime (n*s) | Filter | Magnitude | UL (3sigma) | | ---------- | -------- | ---------------- | ------------- | ------ | --------- | ----------- | | 2024-12-15 | 14:27:52 | 0.044875 | 30*120 | R | n/d | 21.3 |

The magnitudes were calibrated using nearby stars from USNO-B1.0 (R2 magnitudes) and are not corrected for the Galactic extinction.

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