A mildly relativistic radio jet from the otherwise normal type Ic supernova 2007gr

作者：Paragi Z^*; Taylor G B; Kouveliotou C; Granot J; Ramirez Ruiz E; Bietenholz M; van der Horst A J; Pidopryhora Y; van Langevelde H J; Garrett M A; Szomoru A; Argo M K; Bourke S; Paczynski B

来源：Nature, 2010, 463(7280): 516-518.

DOI：10.1038/nature08713

The class of type Ic supernovae have drawn increasing attention since 1998 owing to their sparse association (only four so far) with long duration gamma-ray bursts (GRBs)(1-4). Although both phenomena originate from the core collapse of a massive star, supernovae emit mostly at optical wavelengths, whereas GRBs emit mostly in soft gamma-rays or hard X-rays. Though the GRB central engine generates ultra-relativistic jets, which beam the early emission into a narrow cone, no relativistic outflows have hitherto been found in type Ib/c supernovae explosions, despite theoretical expectations(5-7) and searches(8). Here we report radio (interferometric) observations that reveal a mildly relativistic expansion in a nearby type Ic supernova, SN 2007gr. Using two observational epochs 60 days apart, we detect expansion of the source and establish a conservative lower limit for the average apparent expansion velocity of 0.6c. Independently, a second mildly relativistic supernova has been reported(9). Contrary to the radio data, optical observations(10-13) of SN 2007gr indicate a typical type Ic supernova with ejecta velocities similar to 6,000 km s(-1), much lower than in GRB-associated supernovae. We conclude that in SN 2007gr a small fraction of the ejecta produced a low-energy mildly relativistic bipolar radio jet, while the bulk of the ejecta were slower and, as shown by optical spectropolarimetry(14), mildly aspherical.

• 出版日期2010-1-28