Early measurements of SN 1987A can be interpreted in light of the beam/jet ( BJ ) which had to hit polar ejecta ( PE ) to produce the “ Mystery Spot ” ( MS ) , some 22 light-days distant .
It takes an extra eight days for the SN flash to hit the MS , and early measurements confirm 2 \times 10 ^ { 39 } ergs/s in the optical for a day at day 8 , before dropping off by day 8.5 .
A linear ramp in luminosity starting near day 10 indicates particles from the BJ hitting the PE , with the fastest particles traveling at 0.8 c , and an upper limit for the optical luminosity of the MS of 5 \times 10 ^ { 40 } ergs/s , about 23 % of the total of 2.1 \times 10 ^ { 41 } ergs/s at day 20 .
The many 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 is a mechanism which can produce \ell GRBs .
A 0.5 ^ { \circ } offset , the typical collimation for a GRB , over the 22 light-days from SN 1987A to its PE , produces \sim 100 s of delay , matching the observed delay of the non-prompt parts of \ell GRBs .
Because DD must be the overwhelmingly dominant SN mechanism in elliptical galaxies ( EGs ) , where only short , hard GRBs ( sGRBs ) have been observed , DD without CE or PE must also produce sGRBs , and thus the initial photon spectrum of 99 % of all GRBs is known , and neutron star ( NS ) -NS mergers may not make GRBs as we know them .
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 EGs .
The many details of Ia ’ s strongly suggest that these are also DD .
This is a concern for systematics 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 ( otherwise it would just beg the question of what else they could possibly be , and other mechanisms , such as “ delayed detonation ” or “ gravitationally confined detonation , ” don ’ t produce the inverse relation between polarization and luminosity ) .
As a DD-initiated SN , 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 to account for GRBs .