Sarp Akçay
A5021774275- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Black Holes and Theoretical Physics
- Geophysics and Gravity Measurements
- High-pressure geophysics and materials
- Cosmology and Gravitation Theories
- Relativity and Gravitational Theory
- Magnetic confinement fusion research
- Astrophysics and Cosmic Phenomena
- Geophysics and Sensor Technology
- Seismic Imaging and Inversion Techniques
- Statistical and numerical algorithms
- Quantum and Classical Electrodynamics
- Radio Astronomy Observations and Technology
- Algebraic and Geometric Analysis
- Gaussian Processes and Bayesian Inference
- Particle physics theoretical and experimental studies
University College Dublin
2015-2025
Friedrich Schiller University Jena
2018-2023
University of Southampton
2011-2015
Institut des Hautes Études Scientifiques
2012
The University of Texas at Austin
2009-2011
On May 21, 2019 at 03:02:29 UTC Advanced LIGO and Virgo observed a short duration gravitational-wave signal, GW190521, with three-detector network signal-to-noise ratio of 14.7, an estimated false-alarm rate 1 in 4900 yr using search sensitive to generic transients. If GW190521 is from quasicircular binary inspiral, then the detected signal consistent merger two black holes masses 85_{-14}^{+21} M_{⊙} 66_{-18}^{+17} (90% credible intervals). We infer that primary hole mass lies within gap...
We report on the population properties of compact binary mergers inferred from gravitational-wave observations these systems during first three LIGO-Virgo observing runs. The Gravitational-Wave Transient Catalog 3 (GWTC-3) contains signals consistent with classes mergers: black hole, neutron star, and star–black hole mergers. infer star merger rate to be between 10 <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mn>1700</a:mn><a:mtext> </a:mtext><a:mtext>...
We report on gravitational wave discoveries from compact binary coalescences detected by Advanced LIGO and Virgo in the first half of third observing run (O3a) between 1 April 2019 15:00 UTC October 15:00. By imposing a false-alarm-rate threshold two per year each four search pipelines that constitute our search, we present 39 candidate events. At this threshold, expect contamination fraction less than 10%. Of these, 26 events were reported previously near real-time through GCN Notices...
We report the observation of gravitational waves from a binary-black-hole coalescence during first two weeks LIGO's and Virgo's third observing run. The signal was recorded on April 12, 2019 at 05:30:44 UTC with network signal-to-noise ratio 19. binary is different observations runs most notably due to its asymmetric masses: ~30 solar mass black hole merged ~8 companion. more massive rotated dimensionless spin magnitude between 0.22 0.60 (90% probability). Asymmetric systems are predicted...
Abstract We report the observation of a compact binary coalescence involving 22.2–24.3 M ⊙ black hole and object with mass 2.50–2.67 (all measurements quoted at 90% credible level). The gravitational-wave signal, GW190814, was observed during LIGO’s Virgo’s third observing run on 2019 August 14 21:10:39 UTC has signal-to-noise ratio 25 in three-detector network. source localized to 18.5 deg 2 distance Mpc; no electromagnetic counterpart been confirmed date. most unequal yet measured...
We present TEOBResumS, a new effective-one-body (EOB) waveform model for nonprecessing (spin-aligned) and tidally interacting compact binaries.Spin-orbit spin-spin effects are blended together by making use of the concept centrifugal EOB radius. The point-mass sector through merger ringdown is informed numerical relativity (NR) simulations binary black holes (BBH) computed with SpEC BAM codes. An improved, NR-based phenomenological description postmerger developed.The tidal TEOBResumS...
Abstract We report the observation of a coalescing compact binary with component masses 2.5–4.5 M ⊙ and 1.2–2.0 (all measurements quoted at 90% credible level). The gravitational-wave signal GW230529_181500 was observed during fourth observing run LIGO–Virgo–KAGRA detector network on 2023 May 29 by LIGO Livingston observatory. primary source has mass less than 5 99% credibility. cannot definitively determine from data alone whether either is neutron star or black hole. However, given...
We present results from calculations of the orbital evolution in eccentric binaries nonrotating black holes with extreme mass-ratios. Our inspiral model is based on method osculating geodesics, and first to incorporate full gravitational self-force (GSF) effect, including conservative corrections. The GSF information encapsulated an analytic interpolation formula numerical data for over a thousand sample geodesic orbits. assess importance corrections waveform models gravitational-wave searches.
We compute the conservative piece of gravitational self-force (GSF) acting on a particle mass ${m}_{1}$ as it moves along an (unstable) circular geodesic orbit between innermost stable and light ring Schwarzschild black hole ${m}_{2}\ensuremath{\gg}{m}_{1}$. More precisely, we construct function ${h}_{uu}^{R,L}(x)\ensuremath{\equiv}{h}_{\ensuremath{\mu}\ensuremath{\nu}}^{R,L}{u}^{\ensuremath{\mu}}{u}^{\ensuremath{\nu}}$ (related to Detweiler's gauge-invariant ``redshift'' variable), where...
Spin precession is a generic feature of compact binary coalescences that leaves clear imprints in the gravitational waveforms. Building on previous work, we present an efficient time domain inspiral-merger-ringdown effective-one-body model for precessing black holes, which incorporates subdominant modes beyond $\ensuremath{\ell}=2$, and first frequency approximant neutron stars. We validate our against 99 ``short'' numerical relativity waveforms, where find median mismatches...
It is now widely accepted that the universe as we understand it accelerating in expansion and fits de Sitter model rather well. As such, a realistic assumption of black holes must place them on background not Minkowski typically done general relativity. The most astrophysically relevant hole uncharged, rotating Kerr solution, member more Kerr–Newman metrics. A generalization to solution Einstein's equation with cosmological constant Λ was discovered by Carter (1973 Les Astres Occlus ed B...
Gravitational-wave astronomy with coalescing binary neutron star (NS) sources requires the availability of gravitational waveforms tidal effects accurate up to merger. This article presents an improved version TEOBResum, a nonspinning effective-one-body (EOB) waveform model enhanced analytical information in its sector. The potential governing conservative dynamics employs resummed expressions based on post-Newtonian (PN) and self-force (GSF) information. In particular, we compute...
Spinning neutron stars acquire a quadrupole moment due to their own rotation. This quadratic-in-spin, self-spin effect depends on the equation of state (EOS) and affects orbital motion rate inspiral star binaries. We incorporate EOS-dependent (or monopole-quadrupole) terms in spin-aligned effective-one-body (EOB) waveform model TEOBResumS at next-to-next-to-leading (NNLO) order, together with other (bilinear, cubic quartic) nonlinear-in-spin effects (at leading LO). The structure Hamiltonian...
Angular momentum and spin precession are expected to be generic features of a significant fraction binary black hole systems. As such, it is essential have waveform models that faithfully incorporate the effects precession. Here, we assess how well current state-of-the-art achieve this for strains constructed only from $\ensuremath{\ell}=2$ multipoles. Specifically, conduct survey on faithfulness seobnrv5phm, teobresums, imrphenomtphm, imrphenomxphm numerical relativity (NR) surrogate...
The gravitational self-force (GSF) and post-Newtonian (PN) schemes are complementary approximation methods for modeling the dynamics of compact binary systems. Comparison their results in an overlapping domain validity provides a crucial test both can be used to enhance accuracy, e.g. via determination previously unknown PN parameters. Here, first time, we extend such comparisons noncircular orbits---specifically, system two nonspinning objects bound (eccentric) orbit. To enable comparison...
We present the gravitational-wave flux balance law in an extreme mass-ratio binary with a spinning secondary. This relates of energy (angular momentum) radiated to null infinity and through event horizon local change secondary's orbital for generic, nonresonant bound orbits Kerr spacetime. As explicit example we compute these quantities spin-aligned body moving on circular orbit around Schwarzschild black hole. perform this calculation both analytically, via high-order post-Newtonian...
LISA, the Laser Interferometer Space Antenna, will usher in a new era gravitational-wave astronomy. As first anticipated space-based detector, it expand our view to millihertz sky, where spectacular variety of interesting sources abound: from millions ultra-compact binaries Galaxy, mergers massive black holes at cosmological distances; beginnings inspirals that venture into ground-based detectors' death spiral compact objects holes, and many between. Central realising LISA's discovery...
State-of-the-art computations of the gravitational self-force (GSF) on massive particles in black hole spacetimes involve numerical evolution metric perturbation equations time domain, which is computationally very costly. We present here a new strategy based frequency-domain treatment equations, offers considerable computational saving. The essential ingredients our method are (i) Fourier-harmonic decomposition Lorenz-gauge and solution resulting coupled set ordinary with suitable boundary...
Fast, reliable orbital evolutions of compact objects around massive black holes will be needed as input for gravitational wave search algorithms in the data stream generated by planned Laser Interferometer Space Antenna (LISA). Currently, state art is a time-domain code [Phys. Rev. D{\bf 81}, 084021, (2010)] that computes self-force on point-particle an eccentric orbit Schwarzschild hole. codes take up to few days compute just one point parameter space. In series articles, we advocate use...
We consider spin-orbit ("geodetic") precession for a compact binary in strong-field gravity. Specifically, we compute $\psi$, the ratio of accumulated spin-precession and orbital angles over one radial period, spinning body mass $m_1$ spin $s_1$, with $s_1 \ll G m_1^2/c$, orbiting non-rotating black hole. show that $\psi$ can be computed eccentric orbits both gravitational self-force post-Newtonian frameworks, results appear to consistent. present expansion at next-to-next-to-leading order,...
Gravitational waveform (GW) models are a core ingredient for the analysis of compact binary mergers observed by current ground-based interferometers. We focus here on specific class such known as PhenomX, which has gained popularity in recent years thanks to its computational efficiency. introduce new description ``twisting-up'' mapping underpinning construction precessing waveforms within this family. The is an adaptation frequency domain technique previously implemented time-domain models,...
We propose, within the effective-one-body approach, a new, resummed analytical representation of gravitational-wave energy flux absorbed by system two circularized (nonspinning) black holes. This expression is such that it well-behaved in strong-field, fast-motion regime, notably up to effective-one-body-defined last unstable orbit. Building conceptually upon procedure adopted resum multipolar asymptotic flux, we introduce multiplicative decomposition made three factors: (i) leading-order...
The effective-one-body theory (EOB) describes the conservative dynamics of compact binary systems in terms an effective Hamiltonian approach. for moderately eccentric motion two non-spinning objects extreme mass-ratio limit is given three potentials: $a(v), \bar{d}(v), q(v)$. By generalizing first law mechanics (non-spinning) black hole binaries to orbits, [\prd{\bf92}, 084021 (2015)] recently obtained new expressions $\bar{d}(v)$ and $q(v)$ quantities that can be readily computed using...
We present an expression for the gravitational self-force correction to geodetic spin precession of a spinning compact object with small, but non-negligible mass in bound, equatorial orbit around Kerr black hole. consider only conservative backreaction effects due (${m}_{1}$), thus neglecting its ${s}_{1}$ on motion; i.e., we impose ${s}_{1}\ensuremath{\ll}G{m}_{1}^{2}/c$ and ${m}_{1}\ensuremath{\ll}{m}_{2}$, where ${m}_{2}$ is parameter background spacetime. encapsulate $\ensuremath{\psi}$,...