Probing the progenitors of spinning binary black-hole mergers with long gamma-ray bursts


Bavera, Fragos, Zapartas et al. (2022)


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 sub-population 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 LIGO and Virgo 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. The proposed link between a potentially significant fraction of observed, luminous long gamma-ray bursts and the progenitors of spinning binary black-hole mergers allows us to probe the latter well outside the horizon of current-generation gravitational wave observatories, and out to cosmological distances.

Joint distribution of the chirp mass M_\mathrm{chirp} and the effective inspiral spin parameter \chi_\mathrm{eff} from isolated binary evolution. The model predictions for the underlying (intrinsic) binary black hole population is shown in gray where lighter colors represent larger contour levels of 90% and 99.9%, respectively. The sub-population of merging binary black holes which emitted long-duration gamma ray bursts is shown in blue. Overlaid in black are the ten LIGO and Virgo GWTC-2 data with chances p_\mathrm{LGRB}^\mathrm{GWTC-2} > 10 \% to have emitted a luminous long-duration gamma ray burst at binary black hole formation are indicated in black with their 90% credible intervals.