TITLE: GCN CIRCULAR NUMBER: 37536 SUBJECT: GRB 240825A: The nature of the afterglow motivates the search of the associated supernova DATE: 24/09/17 16:54:17 GMT FROM: Remo Ruffini at ICRA ruffini@icra.it

R. Ruffini, C.L. Bianco, M. Della Valle, Liang Li, M.T. Mirtorabi, R. Moradi, F. Rastegar Nia, J.A. Rueda, Y. Wang, on behalf of the ICRANet team, report:

The T90 of GRB 240825A is only 4 seconds (GCN 37301), and it is located at a relatively close distance (z=0.659, GCN 37293). The fluence reaches a high level of 10^{-4} erg/cm^2. Through spectral analysis, we find that peak energy Ep is about 400 keV and isotropic energy Eiso is about 2x10^{53} erg, consistent with the Amati relation for long-duration gamma-ray bursts. Comparing its X-ray afterglow (see figure attached below, blue dots), its luminosity falls within the range of other long-duration bursts which are associated with supernovae, higher than those of short-duration bursts which have merge origins. Based on these findings, we conclude that GRB 240825A is a long-duration burst (BdHN I; see, e.g., Bianco, et al., 2024, ApJ, 966, 219) and is associated with a SN. The supernova may reach its optical peak in the observer's rest-frame approximately one month after the trigger. Its peak brightness should be within the detection limits of both ground- and space-based telescopes. Therefore, we encourage further observations in the coming weeks.

Figure: https://www.icranet.org/documents/GRB_240825A.png

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