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Éanna É. Flanagan

Bio: Éanna É. Flanagan is an academic researcher from Cornell University. The author has contributed to research in topics: Gravitational wave & Gravitation. The author has an hindex of 49, co-authored 142 publications receiving 9940 citations. Previous affiliations of Éanna É. Flanagan include California Institute of Technology & University of Chicago.


Papers
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Journal ArticleDOI
TL;DR: This work investigates how accurately the distance to the source and the masses and spins of the two bodies will be measured from the inspiral gravitational wave signals by the three-detector LIGO-VIRGO network using ``advanced detectors'' (those present a few years after initial operation).
Abstract: The most promising source of gravitational waves for the planned kilometer-size laser-interferometer detectors LIGO and VIRGO are merging compact binaries, i.e., neutron-star--neutron-star (NS-NS), neutron-star--black-hole (NS-BH), and black-hole--black-hole (BH-BH) binaries. We investigate how accurately the distance to the source and the masses and spins of the two bodies will be measured from the inspiral gravitational wave signals by the three-detector LIGO-VIRGO network using ``advanced detectors'' (those present a few years after initial operation). The large number of cycles in the observable waveform increases our sensitivity to those parameters that affect the inspiral rate, and thereby the evolution of the waveform's phase. These parameters are thus measured much more accurately than parameters which affect the waveform's polarization or amplitude. To lowest order in a post-Newtonian expansion, the evolution of the waveform's phase depends only on the combination scrM\ensuremath{\equiv}(${\mathit{M}}_{1}$${\mathit{M}}_{2}$${)}^{3/5}$(${\mathit{M}}_{1}$+${\mathit{M}}_{2}$${)}^{\mathrm{\ensuremath{-}}1/5}$ of the masses ${\mathit{M}}_{1}$ and ${\mathit{M}}_{2}$ of the two bodies, which is known as the ``chirp mass.'' To post-1-Newtonian order, the waveform's phase also depends sensitively on the binary's reduced mass \ensuremath{\mu}\ensuremath{\equiv}${\mathit{M}}_{1}$${\mathit{M}}_{2}$/(${\mathit{M}}_{1}$+${\mathit{M}}_{2}$) allowing, in principle, a measurement of both ${\mathit{M}}_{1}$ and ${\mathit{M}}_{2}$ with high accuracy.We show that the principal obstruction to measuring ${\mathit{M}}_{1}$ and ${\mathit{M}}_{2}$ is the post-1.5-Newtonian effect of the bodies' spins on the waveform's phase, which can mimic the effects that allow \ensuremath{\mu} to be determined. The chirp mass is measurable with an accuracy \ensuremath{\Delta}scrM/scrM\ensuremath{\approxeq}0.1%--1%. Although this is a remarkably small error bar, it is \ensuremath{\sim}10 times larger than previous estimates of \ensuremath{\Delta}scrM/scrM which neglected post-Newtonian effects. The reduced mass is measurable to \ensuremath{\sim}10%--15% for NS-NS and NS-BH binaries, and \ensuremath{\sim}50% for BH-BH binaries (assuming 10${\mathit{M}}_{\mathrm{\ensuremath{\bigodot}}}$ BH's). Measurements of the masses and spins are strongly correlated; there is a combination of \ensuremath{\mu} and the spin angular momenta that is measured to within \ensuremath{\sim}1%. Moreover, if both spins were somehow known to be small (\ensuremath{\lesssim}0.01${\mathit{M}}_{1}^{2}$ and \ensuremath{\lesssim}0.01${\mathit{M}}_{2}^{2}$, respectively), then \ensuremath{\mu} could be determined to within \ensuremath{\sim}1%. Finally, building on earlier work of Markovi\ifmmode \acute{c}\else \'{c}\fi{}, we derive an approximate, analytic expression for the accuracy \ensuremath{\Delta}D of mesurements of the distance D to the binary, for an arbitrary network of detectors. This expression is accurate to linear order in 1/\ensuremath{\rho}, where \ensuremath{\rho} is the signal-to-noise ratio. We also show that, contrary to previous expectations, contributions to \ensuremath{\Delta}D/D that are nonlinear in 1/\ensuremath{\rho} are significant, and we develop an approximation scheme for including the dominant of these nonlinear effects. Using a Monte Carlo simulation we estimate that distance measurement accuracies will be \ensuremath{\le}15% for \ensuremath{\sim}8% of the detected signals, and \ensuremath{\le}30% for \ensuremath{\sim}60% of the signals, for the LIGO-VIRGO three-detector network.

1,121 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of a neutron star's internal structure on the phase of the waveform depends only on a single parameter of the star related to its tidal Love number, namely, the ratio of the induced quadrupole moment to the perturbing tidal gravitational field.
Abstract: Ground-based gravitational wave detectors may be able to constrain the nuclear equation of state using the early, low frequency portion of the signal of detected neutron star--neutron star inspirals. In this early adiabatic regime, the influence of a neutron star's internal structure on the phase of the waveform depends only on a single parameter $\ensuremath{\lambda}$ of the star related to its tidal Love number, namely, the ratio of the induced quadrupole moment to the perturbing tidal gravitational field. We analyze the information obtainable from gravitational wave frequencies smaller than a cutoff frequency of 400 Hz, where corrections to the internal-structure signal are less than 10%. For an inspiral of two nonspinning $1.4{M}_{\ensuremath{\bigodot}}$ neutron stars at a distance of 50 Megaparsecs, LIGO II detectors will be able to constrain $\ensuremath{\lambda}$ to $\ensuremath{\lambda}\ensuremath{\le}2.0\ifmmode\times\else\texttimes\fi{}{10}^{37}\text{ }\text{ }\mathrm{g}\text{ }{\mathrm{cm}}^{2}\text{ }{\mathrm{s}}^{2}$ with 90% confidence. Fully relativistic stellar models show that the corresponding constraint on radius $R$ for $1.4{M}_{\ensuremath{\bigodot}}$ neutron stars would be $R\ensuremath{\le}13.6\text{ }\text{ }\mathrm{km}$ (15.3 km) for a $n=0.5$ ($n=1.0$) polytrope with equation of state $p\ensuremath{\propto}{\ensuremath{\rho}}^{1+1/n}$.

863 citations

Journal ArticleDOI
TL;DR: In this article, the authors estimate the expected signal-to-noise ratios (SNRs) from the three phases (inspiral, merger, and ringdown) of coalescing binary black holes (BBHs) for initial and advanced ground-based interferometers (LIGO-VIRGO) and for the space based interferometer LISA.
Abstract: We estimate the expected signal-to-noise ratios (SNRs) from the three phases (inspiral, merger, and ringdown) of coalescing binary black holes (BBHs) for initial and advanced ground-based interferometers (LIGO-VIRGO) and for the space-based interferometer LISA. Ground-based interferometers can do moderate SNR (a few tens), moderate accuracy studies of BBH coalescences in the mass range of a few to about 2000 solar masses; LISA can do high SNR (of order 104), high accuracy studies in the mass range of about 105–108 solar masses. BBHs might well be the first sources detected by LIGO-VIRGO: they are visible to much larger distances—up to 500 Mpc by initial interferometers—than coalescing neutron star binaries (heretofore regarded as the “bread and butter” workhorse source for LIGO-VIRGO, visible to about 30 Mpc by initial interferometers). Low-mass BBHs (up to 50M⊙ for initial LIGO interferometers, 100M⊙ for advanced, 106M⊙ for LISA) are best searched for via their well-understood inspiral waves; higher mass BBHs must be searched for via their poorly understood merger waves and/or their well-understood ringdown waves. A matched filtering search for massive BBHs based on ringdown waves should be capable of finding BBHs in the mass range of about 100M⊙–700M⊙ out to ∼200 Mpc for initial LIGO interferometers, and in the mass range of ∼200M⊙ to ∼3000M⊙ out to about z=1 for advanced interferometers. The required number of templates is of the order of 6000 or less. Searches based on merger waves could increase the number of detected massive BBHs by a factor of the order of 10 over those found from inspiral and ringdown waves, without detailed knowledge of the waveform shapes, using a noise monitoring search algorithm which we describe. A full set of merger templates from numerical relativity simulations could further increase the number of detected BBHs by an additional factor of up to ∼4.

519 citations

Journal ArticleDOI
TL;DR: Improved wave form modeling is needed as a foundation for extracting the waves’ information, but is not necessary for wave detection.
Abstract: Gravitational-wave interferometers are expected to monitor the last three minutes of inspiral and final coalescence of neutron star and black hole binaries at distances approaching cosmological, where the event rate may be many per year. Because the binary’s accumulated orbital phase can be measured to a fractional accuracy ≪10^-3 and relativistic effects are large, the wave forms will be far more complex and carry more information than has been expected. Improved wave form modeling is needed as a foundation for extracting the waves’ information, but is not necessary for wave detection.

342 citations

Journal ArticleDOI
TL;DR: This paper showed that all classical physical predictions of scalar-tensor theories of gravity are conformal-frame invariants, and that the Palatini form of 1/R gravity is invariant to the conformal frame.
Abstract: It has frequently been claimed in the literature that the classical physical predictions of scalar–tensor theories of gravity depend on the conformal frame in which the theory is formulated. We argue that this claim is false, and that all classical physical predictions are conformal-frame invariants. We also respond to criticisms by Vollick (2003 Preprint gr-qc/0312041), in which this issue arises, of our recent analysis of the Palatini form of 1/R gravity.

335 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
B. P. Abbott1, Richard J. Abbott1, T. D. Abbott2, Fausto Acernese3  +1131 moreInstitutions (123)
TL;DR: The association of GRB 170817A, detected by Fermi-GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short γ-ray bursts.
Abstract: On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0×10^{4} years. We infer the component masses of the binary to be between 0.86 and 2.26 M_{⊙}, in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17-1.60 M_{⊙}, with the total mass of the system 2.74_{-0.01}^{+0.04}M_{⊙}. The source was localized within a sky region of 28 deg^{2} (90% probability) and had a luminosity distance of 40_{-14}^{+8} Mpc, the closest and most precisely localized gravitational-wave signal yet. The association with the γ-ray burst GRB 170817A, detected by Fermi-GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short γ-ray bursts. Subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology.

7,327 citations

Journal ArticleDOI
TL;DR: In this article, the authors review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence and tachyon.
Abstract: We review in detail a number of approaches that have been adopted to try and explain the remarkable observation of our accelerating universe. In particular we discuss the arguments for and recent progress made towards understanding the nature of dark energy. We review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence, tachyon, phantom and dilatonic models. The importance of cosmological scaling solutions is emphasized when studying the dynamical system of scalar fields including coupled dark energy. We study the evolution of cosmological perturbations allowing us to confront them with the observation of the Cosmic Microwave Background and Large Scale Structure and demonstrate how it is possible in principle to reconstruct the equation of state of dark energy by also using Supernovae Ia observational data. We also discuss in detail the nature of tracking solutions in cosmology, particle physics and braneworld models of dark energy, the nature of possible future singularities, the effect of higher order curvature terms to avoid a Big Rip singularity, and approaches to modifying gravity which leads to a late-time accelerated expansion without recourse to a new form of dark energy.

5,954 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a review of the most important aspects of the different classes of modified gravity theories, including higher-order curvature invariants and metric affine.
Abstract: Modified gravity theories have received increased attention lately due to combined motivation coming from high-energy physics, cosmology, and astrophysics. Among numerous alternatives to Einstein's theory of gravity, theories that include higher-order curvature invariants, and specifically the particular class of $f(R)$ theories, have a long history. In the last five years there has been a new stimulus for their study, leading to a number of interesting results. Here $f(R)$ theories of gravity are reviewed in an attempt to comprehensively present their most important aspects and cover the largest possible portion of the relevant literature. All known formalisms are presented---metric, Palatini, and metric affine---and the following topics are discussed: motivation; actions, field equations, and theoretical aspects; equivalence with other theories; cosmological aspects and constraints; viability criteria; and astrophysical applications.

4,027 citations

Journal ArticleDOI
TL;DR: A comprehensive survey of recent work on modified theories of gravity and their cosmological consequences can be found in this article, where the authors provide a reference tool for researchers and students in cosmology and gravitational physics, as well as a selfcontained, comprehensive and up-to-date introduction to the subject as a whole.

3,674 citations