Early measurements of SN 1987A can be interpreted in light of the beam/jet ( BJ ) , with a collimation factor > 10 ^ { 4 } , which had to hit polar ejecta ( PE ) to produce the “ Mystery Spot ” ( MS ) , some 24 light-days distant .
Other details of SN 1987A strongly suggest that it resulted from a merger of two stellar cores of a common envelope ( CE ) binary , i.e .
a “ double degenerate ” ( DD ) -initiated SN .
Without having to blast through the CE of Sk -69 ^ { \circ } 202 , it is likely that the BJ would have caused a full , long-soft gamma-ray burst ( \ell GRB ) upon hitting the PE , thus DD can produce \ell GRBs .
Because DD must be the overwhelmingly dominant merger/SN mechanism in elliptical galaxies , where only short , hard GRBs ( sGRBs ) have been observed , DD without CE or PE must also produce sGRBs , and thus the pre-CE/PE impact photon spectrum of 99 % of all GRBs is known , and neutron star ( NS ) -NS mergers may not make GRBs as we know them , and/or be as common as previously thought .
Millisecond pulsars ( MSPs ) in the non-core-collapsed globular clusters are also 99 % DD-formed from white dwarf ( WD ) -WD merger , consistent with their 2.10 ms minimum spin period , the 2.14 ms signal seen from SN 1987A , and sGRBs offset from the centers of elliptical galaxies .
The many details of Ia ’ s strongly suggest that these are also DD initiated , and the single degenerate total thermonuclear disruption paradigm is now in serious doubt as well .
This is a cause for concern in Ia Cosmology , because Type Ia SNe will appear to be Ic ’ s when viewed from their DD merger poles , given sufficient matter above that lost to core-collapse .
As a DD-initiated SN , 1987A appears to be the Rosetta Stone for 99 % of SNe , GRBs and MSPs , including all recent nearby SNe except SN 1986J , and the more distant SN 2006gy .
There is no need to invent exotica , such as “ collapsars , ” to account for GRBs .