2025MNRAS.537.1430S

GRB 200415A, a short and very bright pulse of $\gamma$-rays, has been claimed to be an extragalactic magnetar giant flare (MGF) in the galaxy ${\mathrm{NGC}\, 253}$. However, as the redshift of the transient was not measured, it is possible that the measured location of the transient on the celestial sphere and the location of the local galaxy merely coincided. Thus, its real progenitor could have been arbitrarily far away, leading to a much larger luminosity of the transient, and leaving the standard model of short gamma-ray bursts (sGRBs), the merger of two compact objects, as an explanation for the observations. Prior to that event, three other sGRBs were proposed to be extragalactic MGFs, which, however, had a substantially wider localization error box. A very recent example is GRB 231115A with its error circle projecting on to M82. We compute the probability for the misinterpretation of sGRBs as extragalactic MGFs by simulating synthetic surveys of sGRB observations. Applying five criteria - incorporating factors such as host galaxy star formation rate, gamma-ray burst monitor trigger, GRB duration, isotropic energy release, and fluence - we identify candidates within the simulated surveys that mimic MGF characteristics. In a non-negligible fraction, 12.5 per cent, of the simulated surveys, we identify at least one sGRB with same characteristics as an MGF. Thus, we conclude that the selection criteria proposed in previous works for the identification of extragalactic MGFs, are not sufficient to reject the sGRB hypothesis. However, our analysis cannot prove that a specific one of the previously proposed extragalactic MGFs is an sGRB.