Outflow-Driven Transients from the Birth of Binary Black Holes II: Primary-Induced Accretion Transients

TL;DR

This paper explores optical transients from the birth of binary black holes caused by accretion and disk winds, predicting distinctive light curves that could be detected by future surveys, occurring 1-10 Gyr before gravitational wave signals.

Contribution

It introduces a new model for primary-induced accretion transients from BBH progenitors, focusing on disk-driven emissions distinct from previous wind-driven transient models.

Findings

Optical transients have energies of 10^{47}-3×10^{48} erg.

Transient durations are a few days with magnitudes from -11 to -14.

Detection is feasible if event rates match BBH merger rates.

Abstract

We discuss the electromagnetic radiation from newborn binary black holes (BBHs). As a consequence of the evolution of massive stellar binaries, a binary consisting of a primary black hole (BH) and a secondary Wolf-Rayet star is expected as a BBH progenitor system. We investigate optical transients from the birth of BBHs powered by the Bondi-Hoyle-Lyttleton accretion onto the primary BH, which occur $\sim1-10$ Gyr earlier than gravitational wave signals at the BH-BH merger. When the secondary massive star collapses into a BH, it may eject a fraction of its outer material and may form a disk around the primary BH and induces a powerful disk wind. These primary-induced winds can lead to optical transients with a kinetic energy of $\sim10^{47}-3\times10^{48}$ erg, an ejecta velocity of $10^8-10^9\rm~cm~s^{-1}$, a duration of a few days, and an absolute magnitude ranging from about $-11$ to $-14$. The light curves and late-time spectra of these transients are distinctive from those of ordinary supernovae, and detection of this type of transient is possible by future optical transient surveys if the event rate of this transient is comparable to the merger rate of BBHs. This paper focuses on the emissions from disk-driven transients induced by the primary BH, different from the first paper that focuses on wind-driven transients from the tidally-locked secondary massive star.