Black holes, disks and jets following binary mergers and stellar collapse: The narrow range of EM luminosities and accretion rates

Stuart L. Shapiro

Published 2017-05-12Version 1

We have performed magnetohydrodynamic simulations in general relativity of binary neutron star and binary black hole-neutron star mergers, as well as the magnetorotational collapse of supermassive stars. In many cases the outcome is a spinnng black hole (BH) immersed in a magnetized disk, with a jet emanating from the poles of the BH. While their formation scenarios differ and their BH masses, as well as their disk masses, densities, and magnetic field strengths, vary by orders of magnitude, these features conspire to generate jet Poynting luminosities that all lie in the same, narrow range of $\sim 10^{52\pm1}~{\rm erg ~s^{-1}}$. A similar result applies to their BH accretion rates upon jet launch, which is $\sim 0.1-10~{\rm M_{\odot}~s^{-1}}$. We provide a simple model that explains these unanticipated findings. Interestingly, these luminosities reside in the same narrow range characterizing the observed luminosity distributions of over 400 short and long GRBs with distances inferred from spectroscopic redshifts or host galaxies. This result, together with the GRB lifetimes predicted by the model, supports the belief that a compact binary merger is the progenitor of an SGRB, while a massive, stellar magnetorotational collapse is the progenitor of an LGRB.