Imprints of accretion on gravitational waves from black holes

TL;DR

This paper investigates how mass accretion during black hole formation affects gravitational wave signals, revealing modulations in frequency that encode information about accretion rates and total mass gained.

Contribution

It introduces the analysis of accretion-induced frequency modulations in gravitational waves, providing a method to infer accretion properties from observed signals.

Findings

Frequency evolution is modulated by accretion rate.

Negative branch in the frequency derivative indicates mass increase.

Frequency patterns reveal accretion details.

Abstract

Black holes are superb sources of gravitational wave signals, for example when they are born in stellar collapse. We explore the subtleties that may emerge if mass accretion events increase significantly the mass of the black hole during its gravitational wave emission. We find the familiar damped-oscillatory radiative decay but now both decay rate and frequencies are modulated by the mass accretion rate. Any appreciable increase in the horizon mass during emission reflects on the instantaneous signal frequency, which shows a prominent negative branch in the dot[f](f) evolution diagram. The features of the frequency evolution pattern reveal key properties of the accretion event, such as the total accreted mass and the accretion rate. For slow accretion rates the frequency evolution follows verbatim the accretion rate, as expected from dimensional arguments. In view of the possibility of detection of black hole ``ringing'' by the upcoming gravitational wave experiments, the deciphering of the late time frequency dynamics may provide direct insight into otherwise obscured aspects of the black hole birth process.