Pulsar Timing Arrays and the Challenge of Massive Black Hole Binary Astrophysics

Sesana, Alberto

doi:10.1007/978-3-319-10488-1_13

Cited by 20 publications

(15 citation statements)

References 66 publications

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“…Since the evolution of a binary orbit strongly depends on the evolution of the eccentricity, this may change the shape of the spectrum. In fact, larger contributions from higher harmonics effectively suppress power at lower frequencies, leading to a low frequency flattening or even a turnover in the spectrum (Enoki & Nagashima 2007;Sesana 2010Sesana , 2015. Therefore, it is necessary to take into account such effects of the eccentricity for more realistic estimates of the GWB.…”

Section: Gws From Eccentric Orbitsmentioning

confidence: 99%

Interactions between multiple supermassive black holes in galactic nuclei: a solution to the final parsec problem

Ryu

Perna

Haiman

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Using few-body simulations, we investigate the evolution of supermassive black holes (SMBHs) in galaxies (M = 10 10 − 10 12 M at z = 0) at 0 < z < 4. Following galaxy merger trees from the Millennium simulation, we model BH mergers with two extreme binary decay scenarios for the 'hard binary' stage: a full or an empty loss cone. These two models should bracket the true evolution, and allow us to separately explore the role of dynamical friction and that of multi-body BH interactions on BH mergers. Using the computed merger rates, we infer the stochastic gravitational wave background (GWB). Our dynamical approach is a first attempt to study the dynamical evolution of multiple SMBHs in the host galaxies undergoing mergers with various mass ratios (10 −4 < q < 1). Our main result demonstrates that SMBH binaries are able to merge in both scenarios. In the empty loss cone case, we find that BHs merge via multi-body interactions, avoiding the 'final parsec' problem, and entering the PTA band with substantial orbital eccentricity. Our full loss cone treatment, albeit more approximate, suggests that the eccentricity becomes even higher when GWs become dominant, leading to rapid coalescences (binary lifetime 1 Gyr). Despite the lower merger rates in the empty loss cone case, due to their higher mass ratios and lower redshifts, the GWB in the full/empty loss cone models are comparable (0.70 × 10 −15 and 0.53 × 10 −15 at a frequency of 1 yr −1 , respectively). Finally, we compute the effects of high eccentricities on the GWB spectrum.

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Section: Gws From Eccentric Orbitsmentioning

confidence: 99%

Interactions between multiple supermassive black holes in galactic nuclei: a solution to the final parsec problem

Ryu

Perna

Haiman

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Spinning binary black holes (BBHs) are a promising source of gravitational waves (GWs) [5][6][7] for current and future detectors [8][9][10][11][12][13][14][15]. BBH dynamics is remarkably complex and interesting, especially when both BBHs are spinning.…”

Section: Introductionmentioning

confidence: 99%

Multi-timescale analysis of phase transitions in precessing black-hole binaries

et al. 2015

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The dynamics of precessing binary black holes (BBHs) in the post-Newtonian regime has a strong timescale hierarchy: the orbital timescale is very short compared to the spin-precession timescale which, in turn, is much shorter than the radiation-reaction timescale on which the orbit is shrinking due to gravitational-wave emission. We exploit this timescale hierarchy to develop a multiscale analysis of BBH dynamics elaborating on the analysis of Kesden et al. [Phys. Rev. Lett. 114, 081103 (2015)]. We solve the spin-precession equations analytically on the precession time and then implement a quasiadiabatic approach to evolve these solutions on the longer radiation-reaction time. This procedure leads to an innovative "precession-averaged" post-Newtonian approach to studying precessing BBHs. We use our new solutions to classify BBH spin precession into three distinct morphologies, then investigate phase transitions between these morphologies as BBHs inspiral. These precession-averaged post-Newtonian inspirals can be efficiently calculated from arbitrarily large separations, thus making progress towards bridging the gap between astrophysics and numerical relativity.

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“…LIGO has detected gravitational waves (GWs) from stellarmass binary black hole mergers (Abbott et al 2016). GW sources should exist outside the LIGO frequency (e.g., eLISA Consortium et al 2013;Colpi & Sesana 2017;Schutz 2018), and this series of papers aims at identifying candidate bi-The more massive BSBHs are being constrained with the upper limits from pulsar-timing arrays (e.g., Arzoumanian et al 2014;Zhu et al 2014;Huerta et al 2015;Sesana 2015;Sesana et al 2018;Shannon et al 2015;Arzoumanian et al 2016;Babak et al 2016;Ellis & Ellis 2016;Middleton et al 2016Middleton et al , 2018Rosado et al 2016;Simon & Burke-Spolaor 2016;Taylor et al 2016;Kelley et al 2017b;Mingarelli et al 2017;Arzoumanian et al 2018;Holgado et al 2018;Tiburzi 2018), whereas the less massive BSBHs are among the primary science targets for the planned space-based GW observatories such as LISA (e.g., Sesana et al 2004;Klein et al 2016;Amaro-Seoane et al 2017;Audley et al 2017). They are laboratories to directly test general relativity in the strong field regime and to study the cosmic evolution of galaxies and cosmology (e.g., Baumgarte & Shapiro 2003;Holz & Hughes 2005;Valtonen et al 2008;Hughes 2009;Centrella et al 2010;Babak et al 2011;Amaro-Seoane et al 2013;Arun & Pai 2013;Merritt 2013;…”

Section: Introductionmentioning

confidence: 99%

Constraining sub-parsec binary supermassive black holes in quasars with multi-epoch spectroscopy – III. Candidates from continued radial velocity tests

Guo

Liu

Shen

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Quasars whose broad emission lines show temporal, bulk radial velocity (RV) shifts have been proposed as candidate sub-parsec (sub-pc), binary supermassive black holes (BSBHs). We identified a sample of 16 BSBH candidates based on two-epoch spectroscopy among 52 quasars with significant RV shifts over a few rest-frame years. The candidates showed consistent velocity shifts independently measured from two broad lines (Hβ and Hα or Mg II) without significant changes in the broad-line profiles. Here in the third paper of the series, we present further third-and fourth-epoch spectroscopy for 12 of the 16 candidates for continued RV tests, spanning ∼5-15 yr in the quasars' rest frames. Cross-correlation analysis of the broad Hβ calibrated against [O III] λ5007 suggests that 5 of the 12 quasars remain valid as BSBH candidates. They show broad Hβ RV curves that are consistent with binary orbital motion without significant changes in the broad line profiles. Their broad Hα (or Mg II) lines display RV shifts that are either consistent with or smaller than those seen in broad Hβ. The RV shifts can be explained by a ∼0.05-0.1 pc BSBH with an orbital period of ∼40-130 yr, assuming a mass ratio of 0.5-2 and a circular orbit. However, the parameters are not well constrained given the few epochs that sample only a small portion of the hypothesized binary orbital cycle. The apparent occurrence rate of sub-pc BSBHs is 13±5% among all SDSS quasars, with no significant difference in the subsets with and without single-epoch broad line velocity offsets. Dedicated long-term spectroscopic monitoring is still needed to further confirm or reject these BSBH candidates.

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Pulsar Timing Arrays and the Challenge of Massive Black Hole Binary Astrophysics

Cited by 20 publications

References 66 publications

Interactions between multiple supermassive black holes in galactic nuclei: a solution to the final parsec problem

Interactions between multiple supermassive black holes in galactic nuclei: a solution to the final parsec problem

Multi-timescale analysis of phase transitions in precessing black-hole binaries

Constraining sub-parsec binary supermassive black holes in quasars with multi-epoch spectroscopy – III. Candidates from continued radial velocity tests

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