From wikipedia(http://en.wikipedia.org/wiki/Supernova) :-

"A long-standing puzzle surrounding Type II supernovae is why the compact object remaining after the explosion is given a large velocity away from the epicentre;[96] pulsars, and thus neutron stars, are observed to have high velocities, and black holes presumably do as well, although they are far harder to observe in isolation. The initial impetus can be substantial, propelling an object of more than a solar mass at a velocity of 500 km/s or greater. This indicates an asymmetry in the explosion, but the mechanism by which momentum is transferred to the compact object remains a puzzle."

My Question:- Could the remnant compact high-velocity object simply be the surviving member of a binary pair, flying off at a tangent from the original locality after the companion star has blown away in a supernova?

  • $\begingroup$ No. The observed object that is moving away is the result of a Type II supernovae: the neutron star. $\endgroup$ – Kyle Kanos Jul 13 '14 at 11:00
  • $\begingroup$ What if original pair comprised a stable fast-moving neutron star and a star which supernova'ed (Type II-P) leaving a small undetected neutron star, black hole or no remnant (en.wikipedia.org/wiki/Supernova see Table:Core collapse scenarios by mass and metallicity, based on Heger et al 2003 paper). $\endgroup$ – steveOw Jul 13 '14 at 12:12
  • $\begingroup$ You are conflating Types here. Type II SNe are caused by single stars, Type I SNe occur in binary systems. $\endgroup$ – Kyle Kanos Jul 14 '14 at 1:12
  • $\begingroup$ Sorry I put the wrong link for the 1st wikipedia article. I did not initially mean to bring Type I supernovae into the discussion. How can we be sure that any particular supernova is from a progenitor star which does not have a small binary partner. $\endgroup$ – steveOw Jul 14 '14 at 9:44
  • $\begingroup$ We can tell from the physics if the explosion mechanism. Type II are caused by the collapsed core and does not need a binary. I am not entirely sure, but I think high-mass binaries are extremely rare compared to the number of neutron stars we know about. $\endgroup$ – Kyle Kanos Jul 14 '14 at 11:14

The answer to the original hypothesis is YES it seems feasible but the most-likely explanation is asymmetry (due to some as-yet undiscovered cause) in the supernova explosion of a single progenitor star.

A simplified example model of the original hypothesis expanded and constrained is as follows:-

An original binary system comprises a primary star of approximately 10sm (solar masses) and a smaller companion neutron star of approximately 2 sm. Their orbits are such that the companion attains orbital velocities of up to 500kps, this could be achieved with a maximum separation of 100 MKm.

Then the primary explodes as a supernova leaving a small (e.g. 1sm) remnant neutron star not visible from earth. The 9sm of ejecta forms an expanding spherical shell which quickly (up to 30,000 kps) moves away from the epicentre. Once inside the shell the companion star feels no net gravitational force from it. Therefore the companion star is quickly "released" from most of its previous gravitational bond and flies off with the linear velocity it possessed at the "moment" of explosion but held back somewhat by attraction to the remnant neutron star. For some reason the companion star is visible from earth after the explosion, maybe it retains or acquires rotation or an accretion disk.

So from earth we would see an expanding shell of supernovae ejecta, no visible remnant at the core and a "runaway" neutron star heading at high velocity away from the epicentre.


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