Formation of Stable Magnetars from Binary Neutron Star Mergers

by Bruno Giacomazzo and Rosalba Perna

ApJL 771, L26 (2013)

Abstract: By performing fully general relativistic magnetohydrodynamic simulations of binary neutron star mergers, we investigate the possibility that the end result of the merger is a stable magnetar. In particular, we show that, for a binary composed of two equal-mass neutron stars (NSs) of gravitational mass M ~ 1.2 M and equation of state similar to Shen et al. at high densities, the merger product is a stable NS. Such NS is found to be differentially rotating and ultraspinning with spin parameter J/M2 ~ 0.86, where J is its total angular momentum, and it is surrounded by a disk of ≈0.1 M . While in our global simulations the magnetic field is amplified by about two orders of magnitude, local simulations have shown that hydrodynamic instabilities and the onset of the magnetorotational instability could further increase the magnetic field strength up to magnetar levels. This leads to the interesting possibility that, for some NS mergers, a stable and magnetized NS surrounded by an accretion disk could be formed. We discuss the impact of these new results for the emission of electromagnetic counterparts of gravitational wave signals and for the central engine of short gamma-ray bursts.

Click Here to Access the data

Data include gravitational wave signals for models B0 and B12 (both Zerilli waveforms that were used for figure 4 in the letter and psi4). Other data may be made publicly available in the future if requested.


Exact Riemann Solver for Relativistic MHD

by Bruno Giacomazzo and Luciano Rezzolla

Journal of Fluid Mechanics, 562, 223

This exact solver can provide exact solution for Riemann problems in relativistic MHD using both an ideal fluid EOS and a Synge-type EOS (Meliani et al 2008). This is the first exact riemann solver able to solve any Riemann problem in RMHD. The solutions computed by this code has been used by several numerical relativity group to test their codes or to describe the physics of relativistic plasmas.

If you already have username and password click here to download the code. Otherwise send me an email and I will give you all the information needed to download and use it.

Below you can also find a map of some of the places where it has been used. If you see a mistake or if a place is missing, simply contact me. Thanks!