Accretion and outflow in the gamma ray bursts from black hole binary systems

TL;DR

This paper models long gamma ray bursts from binary black hole systems formed by stellar collapse, highlighting how black hole mergers and accretion processes extend burst duration and produce distinct electromagnetic and gravitational wave signals.

Contribution

It introduces a scenario where binary black hole interactions during stellar collapse lead to prolonged gamma ray bursts with unique observational signatures.

Findings

Two-peaked electromagnetic signals predicted

Black hole mergers can extend gamma ray burst duration

Potential gravitational recoil effects discussed

Abstract

We consider a scenario for the longest duration gamma ray bursts, resulting from the collapse of a massive star in a close binary system with a companion black hole. The primary black hole born during the core collapse is spun up and increases its mass during the fallback of the stellar envelope. The companion black hole provides an additional angular momentum to the envelope, which ultimately makes the core BH spinning with a high Kerr parameter. After the infall and spiral-in, the two black holes merge inside the circumbinary disk. The second episode of mass accretion and final, even larger spin of the post-merger black hole prolongs the gamma ray burst central engine activity. The observed events should have two distinct peaks in the electromagnetic signal, separated by the gravitational wave emission. The gravitational recoil of the burst engine is also possible.