Disks around merging binary black holes: From GW150914 to supermassive black holes

Abstract

We perform magnetohydrodynamic simulations in full general relativity of disk accretion onto nonspinning black hole binaries with mass ratio = 29/36. We survey different disk models which differ in their scale height, total size and magnetic field to quantify the robustness of previous simulations on the initial disk model. Scaling our simulations to LIGO GW150914 we find that such systems could explain possible gravitational wave and electromagnetic counterparts such as the Fermi GBM hard x-ray signal reported 0.4 s after GW150915 ended. Scaling our simulations to supermassive binary black holes, we find that observable flow properties such as accretion rate periodicities, the emergence of jets throughout inspiral, merger and postmerger, disk temperatures, thermal frequencies, and the time delay between merger and the boost in jet outflows that we reported in earlier studies display only modest dependence on the initial disk model we consider here.

Neutrino spin oscillations in external fields in curved spacetime

“…If we suppose that µ = 10 −14 µ B [41], where µ B is the Bohr magneton, then the magnetic field should be in the range (10 3 −10 7 ) G. Even if we take that µ ∼ 10 −19 µ B [42], which is a natural value for a Dirac neutrino with the mass ∼ 1 eV [43], the magnetic field should be as strong as (10 8 − 10 12 ) G. Such magnetic fields are compatible with the results of the numerical simulations of accretion disks carried out in Ref. [39], where B ∼ 10 12 G was used.…”

“…The inner radius of such a disk was found in Ref. [39] to be ∼ 10R S = 10 8 cm, which is comparable with z 0 .…”

“…III, we have demonstrated that the transition probability of neutrino spin oscillations can potentially reach great values. In our simulations we have chosen the parameters of external fields, such as the matter density and the strength of the magnetic field, not exceeding the predictions of the model of accretion disks around BHs [39]. The range of neutrino magnetic moments, required for the enhancement of the transition probability, is also compatible with the values expected for Dirac neutrinos [40,42].…”

Analysis of Sub-threshold Short Gamma-Ray Bursts in Fermi GBM Data

“…Other theories include the triggered collapse of a massive star due to its black hole companion (Janiuk et al 2017), and the fragmentation of the stellar core of a massive star (Loeb 2016; although see Dai et al 2017 andFedrow et al 2017). Lyutikov (2016) has argued that the physical properties necessary to create GW150914-GBM are highly implausible, although Khan et al (2018) surveyed different models of disks around merging BBHs using magnetohydrodynamic simulations and shows that such systems could produce an EM counterpart consistent with the properties of GW150914-GBM. Likewise Veres et al (2016) showed that dissipative photosphere models of GRB emission can accommodate the GBM observations.…”

Limits on Electromagnetic Counterparts of Gravitational-wave-detected Binary Black Hole Mergers

“…Alternatively, the energy source could be entirely of eletromagnetic nature if the BHs are charged (Liebling & Palenzuela 2016;Zhang 2016;Liu et al 2016;Fraschetti 2018). GRMHD simulations have additionally demonstrated that jets are produced from merging BHs if there is some matter around the BHs at the time of merger (Khan et al 2018).…”