TITLE: GCN CIRCULAR NUMBER: 37299 SUBJECT: GRB 240825A: AKO Optical Follow-Up Observations DATE: 24/08/26 15:40:54 GMT FROM: Mohammad Odeh at Al Khatim Observatory M44 mshodeh@gmail.com

Mohammad Odeh (Al-Khatim Observatory, AKO, operated by the International Astronomical Center in Abu Dhabi, UAE), and Nidhal Guessoum (American University of Sharjah, UAE), report:

We followed up our observations (Odeh & Guessoum, GCN 37277) of GRB 240825A (Fermi GBM team, GCN 37273; Gupta et al., GCN 37274; Swift-XRT team, GCN 37290), with our 0.36m f/7.7 robotic telescope, performing 5 observations between 25 August 2024 at 16:48 UT (0.92 hour after the trigger) and 25 August 2024 at 18:57 UT (3.1 hours after the trigger).

We obtained multiple 180-sec exposures in Ic filter. The optical afterglow was fading:

Our measurements are consistent with other reports (Jiang et al., GCN 37275; Lipunov et al., GCN 37279; and Wei et al., GCN 37292).

The following magnitudes were determined using the Atlas catalogue as a reference: ---------------------------------------------------------------------------- ObsTime (mid), t-T0 (hour), Exposure (sec), Filter, Mag & Mag_Err ---------------------------------------------------------------------------- 2024-08-25T16:59Z, 1.1, 7x180s (stacked), Ic, 17.3 +/- 0.15 2024-08-25T17:23Z, 1.5, 7x180s (stacked), Ic, 17.9 +/- 0.18 2024-08-25T17:48Z, 1.9, 7x180s (stacked), Ic, 18.1 +/- 0.13 2024-08-25T18:17Z, 2.4, 7x180s (stacked), Ic, 18.2 +/- 0.13 2024-08-25T18:42Z, 2.8, 7x180s (stacked), Ic, 18.4 +/- 0.17 ----------------------------------------------------------------------------

The magnitudes were not corrected for galactic extinction.

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