TITLE: GCN CIRCULAR NUMBER: 37400 SUBJECT: GRB 240825A: Montarrenti Observatory optical follow-up observations DATE: 24/09/05 20:40:42 GMT FROM: Simone Leonini at Montarrenti Observatory (Siena, Italy) <s.leonini@iol.it> S. Leonini, M. Conti, P. Rosi, L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy, part of UAI/SSV-GRB section), A. Lorini, G. Verna (University of Siena – DSFTA), G. Bonnoli (INAF – Brera Astronomical Observatory) report: As a follow-up of our early observations of the GRB 240825A (Fermi/GBM team, GCN 37273; Gupta et al., GCN 37274; Di Lalla et al., GCN 37288; Evans et al., GCN 37290; Gropp et al., GCN 37294; Kuin et al., GCN 37296; Joshi et al., GCN 37298; Sharma et al., GCN 37301; Frederiks et al., GCN 37302; Chen-Wei et al., GCN 37315; Moss et al., GCN 37355) already reported in GCN 37291, we kept on imaging the afterglow until 2024-08-26 01:32:48 UT with the same set-up and data analysis procedure. Observations were performed under thin cloud cover in the second part of the night. Here is our complete set of measurements: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2024-08-25 21:12:38 UT 5.33 50x40s Rc 19.81 +/-0.10 2024-08-25 21:47:40 UT 5.92 60x40s Rc 19.97 +/-0.11 2024-08-25 22:33:13 UT 6.66 60x40s Rc 20.26 +/-0.12 2024-08-25 23:18:46 UT 7.43 58x40s Rc 20.49 +/-0.16 2024-08-26 00:04:19 UT 8.18 50x40s Rc 20.78 +/-0.22 2024-08-26 00:49:57 UT 8.95 60x40s Rc 20.71 +/-0.19 Along the span of our observations and within our uncertainties, the afterglow evolves in agreement with a power-law decay with a rate alpha=1.87+/-0.20 View this GCN Circular online at https://gcn.nasa.gov/circulars/37400. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...