Co-Author: Rosalba Perna
Neutron stars (NSs) in the astrophysical Universe are often surrounded by accretion disks. Accretion of matter onto a NS may increase its mass above the maximum value allowed by its equation of state, inducing its collapse to a black hole (BH). Here we study this process for the first time, in 3D, and in full general relativity. By considering six different initial configurations, with and without an accretion disk, we investigate the effect of the accretion disk on the dynamics of the NS collapse and its imprint on both the gravitational wave (GW) and electromagnetic (EM) signals that can be emitted by these sources. We show in particular that even if the GW signal will be detectable by ground-based detectors only for sources located in our galaxy, the EM emission could provide sufficient information to distinguish accretion induced collapse (AIC) from the collapse of an unstable NS in vacuum. In fact, our simulations show that, while the latter leaves no appreciable baryonic matter outside the event horizon, an AIC is followed by a phase of rapid accretion of the surviving disk onto the newly formed BH. These events may then also be tantalizing candidates as engines of short Gamma-Ray Bursts.
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