Watson D, Fynbo J P U, Thöne C C, Sollerman J
Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark.
Philos Trans A Math Phys Eng Sci. 2007 May 15;365(1854):1269-75. doi: 10.1098/rsta.2006.1994.
There is strong evidence that long-duration gamma-ray bursts (GRBs) are produced during the collapse of a massive star. In the standard version of the collapsar model, a broad-lined and luminous Type Ic core-collapse supernova (SN) accompanies the GRB. This association has been confirmed in observations of several nearby GRBs. Recent observations show that some long-duration GRBs are different. No SN emission accompanied the long-duration GRBs 060505 and 060614 down to limits fainter than any known Type Ic SN and hundreds of times fainter than the archetypal SN 1998bw that accompanied GRB 980425. Multi-band observations of the early afterglows, as well as spectroscopy of the host galaxies, exclude the possibility of significant dust obscuration. Furthermore, the bursts originated in star-forming galaxies, and in the case of GRB 060505, the burst was localized to a compact star-forming knot in a spiral arm of its host galaxy. We find that the properties of the host galaxies, the long duration of the bursts and, in the case of GRB 060505, the location of the burst within its host, all imply a massive stellar origin. The absence of an SN to such deep limits therefore suggests a new phenomenological type of massive stellar death.
有强有力的证据表明，长持续时间伽马射线暴（GRBs）是在大质量恒星坍缩过程中产生的。在坍缩星模型的标准版本中，一次宽线且明亮的Ic型核心坍缩超新星（SN）伴随着伽马射线暴。这种关联在对几个邻近伽马射线暴的观测中得到了证实。最近的观测表明，一些长持续时间伽马射线暴有所不同。长持续时间伽马射线暴060505和060614没有伴随超新星爆发，其亮度下限比任何已知的Ic型超新星还要暗，比伴随伽马射线暴980425的典型超新星1998bw暗数百倍。对早期余辉的多波段观测以及对宿主星系的光谱分析排除了显著尘埃遮挡的可能性。此外，这些伽马射线暴起源于恒星形成星系，就伽马射线暴060505而言，爆发定位于其宿主星系旋臂中的一个致密恒星形成结。我们发现，宿主星系的性质、伽马射线暴的长时间持续以及（就伽马射线暴060505而言）爆发在其宿主星系中的位置，都暗示着起源于大质量恒星。因此，在如此深的亮度下限下没有超新星爆发，这表明了一种新的大质量恒星死亡的唯象学类型。
