LISA observations of supermassive black holes: parameter estimation using full post-Newtonian inspiral waveforms

We study parameter estimation of supermassive black hole binary systems in the final stage of inspiral using the full post-Newtonian gravitational waveforms. We restrict our analysis to systems in circular orbit with negligible spins, in the mass range 10^8\Ms-10^5\Ms, and compare the results with those arising from the commonly used restricted post-Newtonian approximation. The conclusions of this work are particularly important with regard to the astrophysical reach of future LISA measurements. Our analysis clearly shows that modeling the inspiral with the full post-Newtonian waveform, not only extends the reach to higher mass systems, but also improves in general the parameter estimation. In particular, there are remarkable improvements in angular resolution and distance measurement for systems with a total mass higher than 5\times10^6\Ms, as well as a large improvement in the mass determination.Comment: Final version. Accepted for publication in Phys. Rev.

The Adaptive Transient Hough method for long-duration gravitational wave transients

This paper describes a new semi-coherent method to search for transient gravitational waves of intermediate duration (hours to days). In order to search for newborn isolated neutron stars with their possibly very rapid spin-down, we model the frequency evolution as a power law. The search uses short Fourier transforms from the output of ground-based gravitational wave detectors and applies a weighted Hough transform, also taking into account the signal's amplitude evolution. We present the technical details for implementing the algorithm, its statistical properties, and a sensitivity estimate. A first example application of this method was in the search for GW170817 post-merger signals, and we verify the estimated sensitivity with simulated signals for this case.Comment: 13 pages, 14 figure

El nacimiento de la astronomía de ondas gravitacionales

Los últimos tres años han sido testigos del nacimiento de la astronomía de ondas gravitacionales. Esta nueva era de la astronomía empezó de repente en septiembre de 2015 con la primera detección de una fusión de binarias de agujeros negros situados a 1.300 millones de años luz de distancia. Este descubrimiento causó un revuelo en la comunidad científica, no solo porque confirmaba una importante predicción de la teoría de la relatividad general de Albert Einstein de 1915, sino también por el impacto en el campo de la astronomía de este evento cósmico nunca antes observado. La importancia de este hallazgo dio pie a la concesión de los más prestigiosos premios científicos, incluido el Premio Nobel en Física en 2017. Otro descubrimiento más reciente, el de una fusión de un sistema binario de estrellas de neutrones, detectada conjuntamente por los detectores LIGO y Virgo, seguido de una explosión de rayos gamma y una kilonova, han reforzado la emoción de esta nueva era, en la que pronto esperamos ver otro tipo de fuentes y hacer astronomía de alta precisió

Matched-filter study and energy budget suggest no detectable gravitational-wave 'extended emission' from GW170817

Van Putten & Della Valle (2018) have reported a possible detection of gravitational-wave 'extended emission' from a neutron star remnant of GW170817. Starting from the time-frequency evolution and total emitted energy of their reported candidate, we show that such an emission is not compatible with the current understanding of neutron stars. We explore the additional required physical assumptions to make a full waveform model, for example, taking the optimistic emission from a spining-down neutron star with fixed quadrupolar deformation, and study whether even an ideal single-template matched-filter analysis could detect an ideal, fully phase-coherent signal. We find that even in the most optimistic case an increase in energy and extreme parameters would be required for a confident detection with LIGO sensitivity as of 2018-08-17. The argument also holds for other waveform models following a similar time-frequency track and overall energy budget. Single-template matched filtering on the LIGO data around GW170817, and on data with added simulated signals, verifies the expected sensitivity scaling and the overall statistical expectation.Comment: 9 pages, 6 figures, updated version as accepted by MNRA

Parameter estimation of compact binaries using the inspiral and ringdown waveforms

We analyze the problem of parameter estimation for compact binary systems that could be detected by ground-based gravitational wave detectors. So far this problem has only been dealt with for the inspiral and the ringdown phases separately. In this paper, we combine the information from both signals, and we study the improvement in parameter estimation, at a fixed signal-to-noise ratio, by including the ringdown signal without making any assumption on the merger phase. The study is performed for both initial and advanced LIGO and VIRGO detectors.Comment: matching cqg versio

Infinite Kinematic Self-Similarity and Perfect Fluid Spacetimes

Perfect fluid spacetimes admitting a kinematic self-similarity of infinite type are investigated. In the case of plane, spherically or hyperbolically symmetric space-times the field equations reduce to a system of autonomous ordinary differential equations. The qualitative properties of solutions of this system of equations, and in particular their asymptotic behavior, are studied. Special cases, including some of the invariant sets and the geodesic case, are examined in detail and the exact solutions are provided. The class of solutions exhibiting physical self-similarity are found to play an important role in describing the asymptotic behavior of the infinite kinematic self-similar models.Comment: 38 pages, 6 figures. Accepted for publication in General Relativity & Gravitatio