NRAO: Strange Supernova Is "Missing Link" in GRB Connection

[bystander]

Strange Supernova Is "Missing Link" in Gamma-Ray Burst Connection
National Radio Astronomy Observatory | 2015 Apr 27

[img3="In an ordinary core-collapse supernova with no "central engine," ejected material expands outward nearly spherically, left. At right, a strong central engine propels jets of material at nearly the speed of light and generates a gamma-ray burst (GRB). The center panel shows an intermediate supernova like SN 2012ap, with a weak central engine, weak jets, and no GRB. (Credit: Bill Saxton, NRAO/AUI/NSF)"]http://public.nrao.edu/images/non-galle ... a_nrao.jpg[/img3][hr][/hr]

Astronomers using the National Science Foundation's Very Large Array (VLA) have found a long-sought "missing link" between supernova explosions that generate gamma-ray bursts (GRBs) and those that don't. The scientists found that a stellar explosion seen in 2012 has many characteristics expected of one that generates a powerful burst of gamma rays, yet no such burst occurred.

"This is a striking result that provides a key insight about the mechanism underlying these explosions," said Sayan Chakraborti, of the Harvard-Smithsonian Center for Astrophysics (CfA). "This object fills in a gap between GRBs and other supernovae of this type, showing us that a wide range of activity is possible in such blasts," he added.

The object, called Supernova 2012ap (SN 2012ap) is what astronomers term a core-collapse supernova. This type of blast occurs when the nuclear fusion reactions at the core of a very massive star no longer can provide the energy needed to hold up the core against the weight of the outer parts of the star. The core then collapses catastrophically into a superdense neutron star or a black hole. The rest of the star's material is blasted into space in a supernova explosion.

The most common type of such a supernova blasts the star's material outward in a nearly-spherical bubble that expands rapidly, but at speeds far less than that of light. These explosions produce no burst of gamma rays. ...

A Missing-Link in the Supernova-GRB Connection: The Case of SN 2012ap - Sayan Chakraborti et al

• arXiv.org > astro-ph > arXiv:1402.6336 > 25 Feb 2014 (v1), 23 Apr 2015 (v2)

Relativistic supernovae have shorter-lived central engines or more extended progenitors: the case of SN 2012ap - Raffaella Margutti et al

• Astrophysical Journal 797(2) 107 (2014 Dec 20) DOI: 10.1088/0004-637X/797/2/107
  arXiv.org > astro-ph > arXiv:1402.6344 > 25 Feb 2014 (v1), 06 Nov 2014 (v2)

The Broad-Lined Type Ic SN 2012ap and the Nature of Relativistic Supernovae Lacking a Gamma-ray Burst Detection - Dan Milisavljevic et al

• Astrophysical Journal 799(1) 51 (2015 Jan 20) DOI: 10.1088/0004-637X/799/1/51
  arXiv.org > astro-ph > arXiv:1408.1606 > 07 Aug 2014 (v1), 11 Aug 2014 (v2)