The Polar Regions of Cassiopeia A: The Aftermath of a Gamma‐Ray Burst?

Probably not, but it is interesting nevertheless to investigate just howclose Cas A might have come to generating such an event. Focusing on thenortheast jet filaments, we analyze the polar regions of the recently acquiredvery deep 1 Ms Chandra X-ray observation. We infer that the so-called "jet"regions are indeed due to jets emanating from the explosion center, and not dueto polar cavities in the circumstellar medium at the time of explosion. Weplace limits on the equivalent isotropic explosion energy in the polar regions(around 2.3 x 10^52 ergs), and the opening angle of the x-ray emitting ejecta(around 7 degrees), which give a total energy in the NE jet of order 10^50ergs; an order of magnitude or more lower than inferred for "typical" GRBs.While the Cas A progenitor and explosion exhibit many of the featuresassociated with GRB hosts, e.g. extensive presupernova mass loss and rotation,and jets associated with the explosion, we speculate that the recoil of thecompact central object, with velocity 330 km/s, may have rendered the jetunstable. In such cases the jet rapidly becomes baryon loaded, if not truncatedaltogether. Although unlikely to have produced a gamma ray burst, the jets inCas A suggest that such outflows may be common features of core-collapse SNe.Comment: 35 pages, 7 figures, accepted by Ap