Soft gamma-ray repeaters (SGRs) are a mainly Galactic population and originate from neutron stars with intense (B≃10¹⁵ G) magnetic fields (magnetars). Occasionally, a giant flare occurs with enormous intensity, displaying a short, hard spike followed by a weaker, oscillatory phase that exhibits the rotational period of the neutron star. If the magnetar giant flares occur in nearby galaxies, they would appear as cosmic, short-hard gamma-ray bursts (GRBs) without detecting the weak oscillatory phase. Recently, a short-hard GRB named GRB 200415A was detected, with a position coincident with the Sculptor Galaxy (NGC 253), raising the question of whether it is a classic short GRB or a magnetar giant flare. Here we show that magnetar giant flares follow a scaling relation between the spectral peak energy and the isotropic energy in 1 keV–10 MeV, i.e., , and locate in a distinct region of the E _p–E _iso plane from that of classic short GRBs. The relation can be well understood in the model that giant flares arise from the photosphere emissions of relativistically expanding fireballs. GRB 200415A, together with two other candidate giant flares (GRB 051103 and GRB 070201) follow this relation, which strongly favors the giant flare origin of these GRBs. The GeV emission detected by Fermi/LAT from GRB 200415A at 18–285 s can also be explained in the giant flare scenario. The total energy in the GeV emission implies a baryon load of ∼10²³ g in the giant flare fireball of GRB 200415A.

软伽马射线中继器（SGR中）是一个主要银河人口和激烈的（从中子星起源乙≃10 ¹⁵G）磁场（磁铁）。有时，巨大的耀斑会以巨大的强度发生，表现出短而硬的尖峰，随后是较弱的振荡相，表现出中子星的旋转周期。如果磁星大耀斑出现在附近的星系中，它们将显示为宇宙的短硬伽马射线爆发（GRB），而不会检测到弱的振荡相位。最近，发现了一个名为GRB 200415A的短硬GRB，其位置与Sculptor Galaxy（NGC 253）重合，这引发了一个问题，即它是经典的短GRB还是磁石巨大的耀斑。在这里，我们表明，磁石大耀斑在1 keV–10 MeV中即遵循谱峰值能量和各向同性能量之间的比例关系，并且位于E _p –的不同区域。 与经典短GRB的E _iso平面不同。这种关系可以在模型中很好地理解，巨大的耀斑是由相对论扩张的火球的光球发射引起的。GRB 200415A与其他两个候选巨型火炬（GRB 051103和GRB 070201）一起遵循此关系，这强烈支持这些GRB的巨型火炬起源。Fermi / LAT在18-285 s时从GRB 200415A探测到的GeV排放也可以解释为巨大的耀斑情况。GeV发射中的总能量意味着GRB 200415A的巨大火炬火球中的重子负荷约为10 ²³ g。