Letter

Nature 463, 516-518 (28 January 2010) | doi:10.1038/nature08713; Received 31 August 2009; Accepted 23 November 2009

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

Z. Paragi1,2, G. B. Taylor3, C. Kouveliotou4, J. Granot5, E. Ramirez-Ruiz6, M. Bietenholz7,8, A. J. van der Horst4, Y. Pidopryhora1, H. J. van Langevelde1,10, M. A. Garrett9,10,11, A. Szomoru1, M. K. Argo12, S. Bourke1 & B. Paczyński13

  1. Joint Institute for VLBI in Europe (JIVE), Postbus 2, 7990AA Dwingeloo, The Netherlands
  2. MTA Research Group for Physical Geodesy and Geodynamics, PO Box 91, H-1521 Budapest, Hungary
  3. University of New Mexico, Department of Physics and Astronomy, MSC07 4220, 800 Yale Blvd NE Albuquerque, New Mexico 87131-0001, USA
  4. Space Science Office, NASA/Marshall Space Flight Center, Huntsville, Alabama 38512, USA
  5. Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, Hertfordshire AL10 9AB, UK
  6. Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064, USA
  7. Hartebeesthoek Radio Observatory, PO Box 443, Krugersdorp, 1740, South Africa
  8. Department of Physics and Astronomy, York University, Toronto, Ontario M3J 1P3, Canada
  9. Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, The Netherlands
  10. Leiden Observatory, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands
  11. Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
  12. Curtin Institute of Radio Astronomy, Curtin University of Technology, GPO Box U1987, Perth, Western Australia 6845, Australia
  13. Deceased.

Correspondence to: Z. Paragi1,2 Correspondence and requests for materials should be addressed to Z.P. (Email: zparagi@jive.nl).

The class of type Ic supernovae have drawn increasing attention since 1998 owing to their sparse association (only four so far) with long duration γ-ray bursts (GRBs)1, 2, 3, 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 γ-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 expectations5, 6, 7 and searches8. Here we report radio (interferometric) observations that reveal a mildly relativistic expansion in a nearby type Ic supernova, SN 2007gr. Using two observational epochs 60days 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 reported9. Contrary to the radio data, optical observations10, 11, 12, 13 of SN 2007gr indicate a typical type Ic supernova with ejecta velocities ~6,000kms-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 spectropolarimetry14, mildly aspherical.

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