# The lifetime of binary black holes in Sérsic galaxy models

Biava, Nadia; Colpi, Monica; Capelo, Pedro R; Bonetti, Matteo; Volonteri, Marta; Tamfal, Tomas; Mayer, Lucio; Sesana, Alberto (2019). The lifetime of binary black holes in Sérsic galaxy models. Monthly Notices of the Royal Astronomical Society, 487(4):4985-4994.

## Abstract

In the local Universe, black holes of $10^{5-6}\, {\rm M_\odot }$ are hosted in galaxies displaying a variety of stellar profiles and morphologies. These black holes are the anticipated targets of LISA, the Laser Interferometer Space Antenna that will detect the low-frequency gravitational-wave signal emitted by binary black holes in this mass interval. In this paper, we infer upper limits on the lifetime of binary black holes of $10^{5-6}\, {\rm M_\odot }$ and up to $10^8\, {\rm M_\odot }$, forming in galaxy mergers, exploring two underlying stellar density profiles, by Dehnen and by Prugniel &amp; Simien, and by exploiting local scaling relations between the mass of the black holes and several quantities of their hosts. We focus on the phase of the dynamical evolution when the binary is transitioning from the hardening phase ruled by the interaction with single stars to the phase driven by the emission of gravitational waves. We find that different stellar profiles predict very distinct trends with binary mass, with lifetimes ranging between fractions of a Gyr to more than 10 Gyr, and with a spread of about one order of magnitude, given by the uncertainties in the observed correlations, which are larger in the low-mass tail of the observed black hole population.

## Abstract

In the local Universe, black holes of $10^{5-6}\, {\rm M_\odot }$ are hosted in galaxies displaying a variety of stellar profiles and morphologies. These black holes are the anticipated targets of LISA, the Laser Interferometer Space Antenna that will detect the low-frequency gravitational-wave signal emitted by binary black holes in this mass interval. In this paper, we infer upper limits on the lifetime of binary black holes of $10^{5-6}\, {\rm M_\odot }$ and up to $10^8\, {\rm M_\odot }$, forming in galaxy mergers, exploring two underlying stellar density profiles, by Dehnen and by Prugniel &amp; Simien, and by exploiting local scaling relations between the mass of the black holes and several quantities of their hosts. We focus on the phase of the dynamical evolution when the binary is transitioning from the hardening phase ruled by the interaction with single stars to the phase driven by the emission of gravitational waves. We find that different stellar profiles predict very distinct trends with binary mass, with lifetimes ranging between fractions of a Gyr to more than 10 Gyr, and with a spread of about one order of magnitude, given by the uncertainties in the observed correlations, which are larger in the low-mass tail of the observed black hole population.

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Item Type: Journal Article, refereed, original work 07 Faculty of Science > Institute for Computational Science 530 Physics Physical Sciences > Astronomy and Astrophysics Physical Sciences > Space and Planetary Science English 21 August 2019 14 Feb 2020 08:25 27 Jan 2022 00:40 Oxford University Press 0035-8711 This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2019 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved. Green Publisher DOI. An embargo period may apply. https://doi.org/10.1093/mnras/stz1614

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