If at least one neutron star (NS) is magnetized in a binary NS merger, then the orbital motion of the conducting companion during the final inspiral induces a strong voltage and current along the magnetic field lines connecting the NSs. If a modest fraction η of the extracted electromagnetic power extracted accelerates relativistic particles, the resulting gamma-ray emission a compact volume will result in the formation of an electron-positron pair fireball. Applying a steady-state pair wind model, we quantify the detectability of the precursor fireball with gamma-ray satellites. For η ∼ 1 the gamma-ray detection horizon of D max ≈ 10(B d /10 14 G) 3/4 is much closer than the Advanced LIGO/Virgo horizon of 200 Mpc, unless the NS surface magnetic field strength is very large, B d ∼ > 10 15 G. Given the quasi-isotropic nature of the emission, mergers with weaker NS fields could contribute a nearby population of short gamma-ray bursts. Power not dissipated close to the binary is carried to infinity along the open field lines by a large scale Poynting flux. Reconnection within this outflow, well outside of the pair photosphere, provides a potential site for non-thermal emission, such as a coherent millisecond radio burst.

We perform N-body simulations on some of the most massive galaxies extracted from a cosmological simulation of hierarchical structure formation with total masses in the range 1012M⊙ < Mtot < 3 × 1013M⊙ from 4 ≥ z ≥ 0. After galactic mergers, we track the dynamical evolution of the infalling black holes (BHs) around their host’s central BHs. From 11 different simulations, we find that, of the 86 infalling BHs with masses > 104M⊙, 36 merge with their host’s central BH, 13 are ejected from their host galaxy, and 37 are still orbiting at z = 0. Across all galaxies, 33 BHs are kicked to a higher orbit after close interactions with the central BH binary or multiple, after which only one of them merged with their hosts. These orbiting BHs should be detectable by their anomalous (not Low Mass X-ray Binary) spectra. The X-ray luminosities of the orbiting massive BHs at z = 0 are in the range 1028 − 1043 erg s−1, with a currently undetectable median value of 1033 erg s−1. However, the most luminous ∼5% should be detectable by existing X-ray facilities.

No abstract

If at least one neutron star (NS) is magnetized in a binary NS merger, then the orbital motion of the conducting companion during the final inspiral induces a strong voltage and current along the magnetic field lines connecting the NSs. If a modest fraction η of the extracted electromagnetic power extracted accelerates relativistic particles, the resulting gamma-ray emission a compact volume will result in the formation of an electron-positron pair fireball. Applying a steady-state pair wind model, we quantify the detectability of the precursor fireball with gamma-ray satellites. For η ∼ 1 the gamma-ray detection horizon of D max ≈ 10(B d /10 14 G) 3/4 is much closer than the Advanced LIGO/Virgo horizon of 200 Mpc, unless the NS surface magnetic field strength is very large, B d ∼ > 10 15 G. Given the quasi-isotropic nature of the emission, mergers with weaker NS fields could contribute a nearby population of short gamma-ray bursts. Power not dissipated close to the binary is carried to infinity along the open field lines by a large scale Poynting flux. Reconnection within this outflow, well outside of the pair photosphere, provides a potential site for non-thermal emission, such as a coherent millisecond radio burst.