Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, Massachusetts 02138, USA.
Nature. 2010 Jan 28;463(7280):513-5. doi: 10.1038/nature08714.
Long duration gamma-ray bursts (GRBs) mark the explosive death of some massive stars and are a rare sub-class of type Ibc supernovae. They are distinguished by the production of an energetic and collimated relativistic outflow powered by a central engine (an accreting black hole or neutron star). Observationally, this outflow is manifested in the pulse of gamma-rays and a long-lived radio afterglow. Until now, central-engine-driven supernovae have been discovered exclusively through their gamma-ray emission, yet it is expected that a larger population goes undetected because of limited satellite sensitivity or beaming of the collimated emission away from our line of sight. In this framework, the recovery of undetected GRBs may be possible through radio searches for type Ibc supernovae with relativistic outflows. Here we report the discovery of luminous radio emission from the seemingly ordinary type Ibc SN 2009bb, which requires a substantial relativistic outflow powered by a central engine. A comparison with our radio survey of type Ibc supernovae reveals that the fraction harbouring central engines is low, about one per cent, measured independently from, but consistent with, the inferred rate of nearby GRBs. Independently, a second mildly relativistic supernova has been reported.
长时标伽马射线暴（GRB）标志着一些大质量恒星的爆炸死亡，是 Ibc 型超新星的一个罕见子类。它们的特点是由中央引擎（吸积黑洞或中子星）驱动的高能和准直相对论性外流产生。在观测上，这种外流表现为伽马射线脉冲和长时间的射电余晖。到目前为止，中央引擎驱动的超新星仅通过其伽马射线发射被发现，但预计由于卫星灵敏度有限或准直发射的指向远离我们的视线，更大的超新星群体未被探测到。在这种情况下，通过对具有相对论性外流的 Ibc 型超新星进行无线电搜索，可能会发现未被探测到的 GRB。在这里，我们报告了从看似普通的 Ibc 型超新星 SN 2009bb 中探测到的明亮无线电发射，这需要由中央引擎提供的大量相对论性外流。与我们对 Ibc 型超新星的无线电巡天进行的比较表明，具有中央引擎的超新星比例较低，约为 1%，这是通过独立于但与推断的近邻 GRB 率一致的方法测量得到的。此外，还报告了第二个轻度相对论性超新星。
