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.

LISA observations of massive black holes binaries using post-Newtonian wave-forms

We consider LISA observations of in-spiral signals emitted by massive black hole binary systems in circular orbit and with negligible spins. We study the accuracy with which the source parameters can be extracted from the data stream. We show that the use of waveforms retaining post-Newtonian corrections not only to the phase but also the amplitude can drastically improve the estimation of some parameters.Comment: Latex 2 pages, 1 figure. To appear in: "Third Amaldi Conference on Gravitational Waves". Edt. S. Meshkov; American Institute of Physic

Higher harmonics increase LISA's mass reach for supermassive black holes

Current expectations on the signal to noise ratios and masses of supermassive black holes which the Laser Interferometer Space Antenna (LISA) can observe are based on using in matched filtering only the dominant harmonic of the inspiral waveform at twice the orbital frequency. Other harmonics will affect the signal-to-noise ratio of systems currently believed to be observable by LISA. More significantly, inclusion of other harmonics in our matched filters would mean that more massive systems that were previously thought to be {\it not} visible in LISA should be detectable with reasonable SNRs. Our estimates show that we should be able to significantly increase the mass reach of LISA and observe the more commonly occurring supermassive black holes of masses $\sim 10^8M_\odot.$ More specifically, with the inclusion of all known harmonics LISA will be able to observe even supermassive black hole coalescences with total mass $\sim 10^8 M_\odot (10^9M_\odot)$ (and mass-ratio 0.1) for a low frequency cut-off of $10^{-4}{\rm Hz}$ $(10^{-5}{\rm Hz})$ with an SNR up to $\sim 60$ $(\sim 30)$ at a distance of 3 Gpc. This is important from the astrophysical viewpoint since observational evidence for the existence of black holes in this mass range is quite strong and binaries containing such supermassive black holes will be inaccessible to LISA if one uses as detection templates only the dominant harmonic.Comment: minor corrections mad

A Simple Computer Model for Liquid Lipid Bilayers

We present a simple coarse-grained bead-and-spring model for lipid bilayers. The system has been developed to reproduce the main (gel-liquid) transition of biological membranes on intermediate length scales of a couple of nanometres and is very efficient from a computational point of view. For the solvent environment, two different models are proposed. The first model forces the lipids to form bilayers by confining their heads in two parallel planes. In the second model, the bilayer is stabilised by a surrounding gas of "phantom" solvent beads, which do not interact with each other. This model takes only slightly more computing time than the first one, while retaining the full membrane flexibility. We calculate the liquid-gel phase boundaries for both models and find that they are very similar.Comment: 11 pages, 6 figure

Removing Line Interference from Gravitational Wave Interferometer Data

We describe a procedure to identify and remove a class of interference lines from gravitational wave interferometer data. We illustrate the usefulness of this technique applying it to prototype interferometer data and removing all those lines corresponding to the external electricity main supply and related features.Comment: Latex 6 pages, 5 figures. To appear in: "Gravitational Wave Detection II". Edt. Rie Sasaki; Universal Academy Press, Inc, Tokyo, Japa