To illustrate the various physical processes that occur during NS-NS mergers, we show the evolution of
three different NS-NS merger simulations in Figures 3, 4
, and 5
, taken from Figures 4 – 6 of [144
]. In
Figure 3
, we see the merger of two equal-mass NSs, each of mass
, described by the APR
(Akmal–Pandharipande–Ravenhall) EOS [3
]. In the second panel, clear evidence of “tidal lags” is visible
shortly after first contact, leading to a slightly off-center collision pattern. By the third panel, an ellipsoidal
HMNS has been formed, surrounded by a disk of material of lower density, which gradually relaxes
to form a more equilibrated HMNS by the final panel. In Figure 4
, we see a merger of two
slightly heavier equal-mass NSs with
. In this case, the deeper gravitational
potential limits the amount of mass that goes into the disk, and once a BH is formed (with a
horizon indicated by the dashed blue circle in the final panel) it accretes virtually all of the
rest mass initially present in the two NSs, with only 0.004% of the total remaining outside the
horizon.
In Figure 5, we see the merger of an unequal-mass binary, with masses
and
. In this case, the heavier NS partially disrupts the lighter NS prior to merger, leading to the
secondary NS being accreted onto the primary. In this case, a much more massive disk is formed and, even
after a BH forms in the center of the remnant, a substantial amount of matter, representing 0.85% of the
total mass, remains outside the horizon. Later accretion of this material could potentially release the energy
required to power a SGRB.
http://www.livingreviews.org/lrr-2012-8 |
Living Rev. Relativity 15, (2012), 8
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