一个错误的身份？GRB 060912 A和长短GRB划分的性质
A case of mistaken identity? GRB 060912A and the nature of the long -- short GRB divide
摘要：
我们调查GRB 060912A的起源，它具有观测特性，使其分类为长或短爆发模糊。短持续时间伽玛暴（SGRB）被认为具有通常比长持续时间爆发低的能量，可以在所有年龄的星系中发现，并且可能起源于长持续时间爆发的不同祖先。然而，已经清楚的是，在许多情况下，仅持续时间不足以区分两个群体，导致希望找到额外的突发类型的鉴别器。GRB 060912 A的持续时间为6秒，距离一个明亮的低红移椭圆星系（$z=0.0936$）只有约10角秒，这表明它可能是宿主星系，这将有利于它成为一个短爆发。然而，我们使用VLT对GRB 060912A位置的深度光学成像和光谱学表明，GRB 060912A更可能起源于z=0.937的遥远恒星形成星系，并且很可能是一个长爆发。这表明，在没有进一步支持证据的情况下，将明亮的邻近星系识别为给定伽玛暴的宿主是有风险的。此外，这意味着，在没有安全的识别，“主机”的类型，或更广泛的歧视，依赖于星系红移，可能不是一个很好的指标的真实性质的任何给定的伽玛射线暴。
英文摘要：
We investigate the origin of the GRB 060912A, which has observational properties that make its classification as either a long or short burst ambiguous. Short duration GRBs (SGRBs) are thought to have typically lower energies than long duration bursts, can be found in galaxies with populations of all ages and are likely to originate from different progenitors to the long duration bursts. However, it has become clear that duration alone is insufficient to make a distinction between the two populations in many cases, leading to a desire to find additional discriminators of burst type. GRB 060912A had a duration of 6 s and occurred only ~10 arcsec from a bright, low redshift ($z=0.0936$) elliptical galaxy, suggesting that this may have been the host, which would favour it being a short-burst. However, our deep optical imaging and spectroscopy of the location of GRB 060912A using the VLT shows that GRB 060912A more likely originates in a distant star forming galaxy at z=0.937, and is most likely a long burst. This demonstrates the risk in identifying bright, nearby galaxies as the hosts of given GRBs without further supporting evidence. Further, it implies that, in the absence of secure identifications, "host" type, or more broadly discriminators which rely on galaxy redshifts, may not be good indicators of the true nature of any given GRB.
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