# Kesden, Michael

Permanent URI for this collectionhttps://hdl.handle.net/10735.1/4147

Michael Kesden is an Assistant Professor of Physics. He also serves as a faculty member of the UTD Cosmology, Relativity and Astrophysics Group. Dr. Kesden's research interests and areas of expertise include:

- Theoretical astrophysics and relativity
- Binary black hole formation, evolution, and merger
- Gravitational wave emission and detection
- Stellar tidal disruption by supermassive black holes
- Astrophysical probes of dark-matter dynamics
- Gravitational lensing of the cosmic microwave background

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# Browsing Kesden, Michael by Author "Berti, E."

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Item Distinguishing Black-Hole Spin-Orbit Resonances by their Gravitational-Wave Signatures(American Physical Society, 2014-06-24) Gerosa, D.; O'Shaughnessy, R.; Kesden, Michael; Berti, E.; Sperhake, U.; 0000 0001 2678 2731 (Kesden, M); Kesden, MichaelIf binary black holes form following the successive core collapses of sufficiently massive binary stars, precessional dynamics may align their spins, S₁ and S₂, and the orbital angular momentum L into a plane in which they jointly precess about the total angular momentum J. These spin orientations are known as spin-orbit resonances since S₁, S₂, and L all precess at the same frequency to maintain their planar configuration. Two families of such spin-orbit resonances exist, differentiated by whether the components of the two spins in the orbital plane are either aligned or antialigned. The fraction of binary black holes in each family is determined by the stellar evolution of their progenitors, so if gravitational-wave detectors could measure this fraction they could provide important insights into astrophysical formation scenarios for binary black holes. In this paper, we show that even under the conservative assumption that binary black holes are observed along the direction of J (where precession-induced modulations to the gravitational waveforms are minimized), the waveforms of many members of each resonant family can be distinguished from all members of the other family in events with signal-to-noise ratios ρ ≃10, typical of those expected for the first detections with Advanced LIGO and Virgo. We hope that our preliminary findings inspire a greater appreciation of the capability of gravitational-wave detectors to constrain stellar astrophysics and stimulate further studies of the distinguishability of spin-orbit resonant families in more expanded regions of binary black-hole parameter space.Item Multi-Timescale Analysis of Phase Transitions in Precessing Black-Hole Binaries(American Physical Society, 2015-09-14) Gerosa, D.; Kesden, Michael; Sperhake, U.; Berti, E.; O'Shaughnessy, R.; Kesden, MichaelThe 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.Item Wide Nutation: Binary Black-Hole Spins Repeatedly Oscillating from Full Alignment to Full Anti-Alignment(Institute of Physics Publishing, 2019-04-15) Gerosa, D.; Lima, A.; Berti, E.; Sperhake, U.; Kesden, Michael; O'Shaughnessy, R.; 0000-0002-5987-1471 (Kesden, M); Kesden, MichaelWithin the framework of 2PN black-hole binary spin precession, we explore configurations where one of the two spins oscillates from being completely aligned with the orbital angular momentum to being completely anti-aligned with it during a single precession cycle. This wide nutation is the extreme limit of the generic phenomenon of spin nutation in black-hole binaries. Crucially, wide nutation happens on the short precession time scale and it is not a secular effect due to gravitational-wave radiation reaction. The spins of these binaries, therefore, flip repeatedly as one of these special configurations is entered. Binaries with total mass M, mass ratio q, and dimensionless spin X1(X2) of the more (less) massive black hole are allowed to undergo wide nutation at binary separations r ≤ rwide ≡ [(qX2 - X1)/(1 - q)]2M. Sources that are more likely to nutate widely have similar masses and effective spins close to zero. © 2019 IOP Publishing Ltd.