Probing the progenitors of spinning binary black-hole mergers with long gamma-ray bursts
Long-duration gamma-ray bursts are thought to be associated with the core-collapse of massive, rapidly spinning stars and the formation of black holes. However, efficient angular momentum transport in stellar interiors, currently supported by asteroseismic and gravitational-wave constraints, leads to predominantly slowly-spinning stellar cores. Here, we report on binary stellar evolution and population synthesis calculations, showing that tidal interactions in close binaries not only can explain the observed subpopulation of spinning, merging binary black holes but also lead to long gamma-ray bursts at the time of black-hole formation. Given our model calibration against the distribution of isotropic-equivalent energies of luminous long gamma-ray bursts, we find that ≈10% of the GWTC-2 reported binary black holes had a luminous long gamma-ray burst associated with their formation, with GW190517 and GW190719 having a probability of ≈85% and ≈60%, respectively, being among them. Moreover, given an assumption about their average beaming fraction, our model predicts the rate density of long gamma-ray bursts, as a function of redshift, originating from this channel. For a constant beaming fraction f B  ∼ 0.05 our model predicts a rate density comparable to the observed one, throughout the redshift range, while, at redshift z  ∈ [0, 2.5], a tentative comparison with the metallicity more »
Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Award ID(s):
Publication Date:
NSF-PAR ID:
10367856
Journal Name:
Astronomy & Astrophysics
Volume:
657
Page Range or eLocation-ID:
L8
ISSN:
0004-6361
We present the stellar population properties of 69 short gamma-ray burst (GRB) host galaxies, representing the largest uniformly modeled sample to date. Using theProspectorstellar population inference code, we jointly fit photometry and/or spectroscopy of each host galaxy. We find a population median redshift of$z=0.64−0.32+0.83$(68% confidence), including nine photometric redshifts atz≳ 1. We further find a median mass-weighted age oftm=$0.8−0.53+2.71$Gyr, stellar mass of log(M*/M) =$9.69−0.65+0.75$, star formation rate of SFR =$1.44−1.35+9.37$Myr−1, stellar metallicity of log(Z*/Z) =$−0.38−0.42+0.44$, and dust attenuation of$AV=0.43−0.36+0.85$mag (68% confidence). Overall, the majority of short GRB hosts are star-forming (≈84%), with small fractions that are either transitioning (≈6%) or quiescent (≈10%); however, we observe a much larger fraction (≈40%) of quiescent and transitioning hosts atz≲ 0.25, commensurate with galaxy evolution. We find that short GRB hosts populate the star-forming main sequence of normal field galaxies, but do not include as many high-mass galaxies as the general galaxy population, implying that their binary neutron star (BNS) merger progenitors are dependent on a combination of host star formation and stellar mass. The distribution of ages and redshifts implies a broad delay-time distribution,more »