A Failed Gamma‐Ray Burst with Dirty Energetic Jets Spirited Away? New Implications for the Gamma‐Ray Burst–Supernova Connection from SN 2002ap

(Abridged) SN 2002ap is an interesting event with broad spectral featureslike the famous SN 1998bw / GRB 980425. Here we examine the recently proposedjet hypothesis from SN 2002ap by a spectropolarimetric observation. We showthat jets should be moving at about 0.23c with a jet kinetic energy of ~5 x10^{50} erg, a similar energy scale to the GRB jets. The weak radio emissionfrom SN 2002ap has been used to argue against the jet hypothesis, but we showthat this problem can be avoided. However, the jet cannot be kept ionizedbecause of adiabatic cooling without external photoionization or heatingsource. We found that only the radioactivity of 56Ni is a possible source,indicating that the jet is formed and ejected from central region of the corecollapse. Then we point out that the jet will eventually sweep up enoughinterstellar medium and generate shocks in a few to 10 years, producing strongradio emission that can be spatially resolved, giving us a clear test for thejet hypothesis. Discussions are given on possible implications for the GRB-SNconnection in the case that the jet is real. We suggest existence of twodistinct classes of GRBs from similar core-collapse events but by completelydifferent mechanisms. Cosmologically distant GRBs (~10^{50} erg) are collimatedjets generated by central activity of core collapses. SN 2002ap could be afailed GRB of this type with a large baryon load. On the other hand, much lessenergetic ones like GRB 980425 are rather isotropic, which may be produced byhydrodynamical shock acceleration at the outer envelope. We propose that theradioactive ionization for the SN 2002ap jet may give a new explanation alsofor the X-ray line features often observed in GRB afterglows.Comment: 14 pages, 5 figures. Version accepted to Ap