Michele's wiki/blog

Authors: P. Patel, X. Siemens, R. Dupuis, J. Betzwieser

Date: 21 Dec 2009

Abstract: We describe an efficient implementation of a coherent statistic for continuous gravitational wave searches from neutron stars. The algorithm works by transforming the data taken by a gravitational wave detector from a moving Earth bound frame to one that sits at the Solar System barycenter. Many practical difficulties arise in the implementation of this algorithm, including constraints of small computer memory, discreteness of the data, losses due to interpolation and gaps in real data. This implementation is considerably more efficient than previous implementations of these kinds of searches.

abs pdf

Authors: Yi Pan, Alessandra Buonanno, Luisa T. Buchman, Tony Chu, Lawrence E. Kidder, Harald P. Pfeiffer, Mark A. Scheel

Date: 17 Dec 2009

Abstract: We present the first attempt at calibrating the effective-one-body (EOB) model to accurate numerical-relativity simulations of spinning, non-precessing black-hole binaries. Aligning the EOB and numerical waveforms at low frequency over a time interval of 1000M, we first estimate the phase and amplitude errors in the numerical waveforms and then minimize the difference between numerical and EOB waveforms by calibrating a handful of EOB-adjustable parameters. In the equal-mass, spin aligned case, we find that phase and fractional amplitude differences between the numerical and EOB (2,2) mode can be reduced to 0.01 radians and 1%, respectively, over the entire inspiral waveforms. In the equal-mass, spin anti-aligned case, these differences can be reduced to 0.13 radians and 1% during inspiral and plunge, and to 0.4 radians and 10% during merger and ringdown. The waveform agreement is within numerical errors in the spin aligned case while slightly over numerical errors in the spin anti-aligned case. Using Enhanced LIGO and Advanced LIGO noise curves, we find that the overlap between the EOB and the numerical (2,2) mode, maximized over the initial phase and time of arrival, is larger than 0.999 for binaries with total mass 30-200Ms. In addition to the leading (2,2) mode, we compare four subleading modes. We find good amplitude and frequency agreements between the EOB and numerical modes for both spin configurations considered, except for the (3,2) mode in the spin anti-aligned case. We believe that the larger difference in the (3,2) mode is due to the lack of knowledge of post-Newtonian spin effects in the higher modes.

abs pdf

Authors: V. Ferrari, L. Gualtieri, F. Pannarale

Date: 18 Dec 2009

Abstract: We study the tidal disruption of neutron stars in black hole-neutron star coalescing binaries. We calculate the critical orbital separation at which the star is disrupted by the black hole tidal field for several equations of state describing the matter inside the neutron star, and for a large set of the binary parameters. When the disruption occurs before the star reaches the innermost stable circular orbit, the gravitational wave signal emitted by the system is expected to exhibit a cutoff frequency nu_GWtide, which is a distinctive feature of the waveform. We evaluate nu_GWtide and show that, if this frequency will be found in a detected gravitational wave, it will allow to determine the neutron star radius with an error of a few percent, providing valuable information on the behaviour of matter in the stellar core.

abs pdf

Authors: Enrico Barausse, Alessandra Buonanno (Univ. of Maryland)

Date: 17 Dec 2009

Abstract: Building on a recent paper in which we computed the canonical Hamiltonian of a spinning test particle in curved spacetime, at linear order in the particle's spin, we work out an improved effective-one-body (EOB) Hamiltonian for spinning black-hole binaries. As in previous descriptions, we endow the effective particle not only with a mass m, but also with a spin S*. Thus, the effective particle interacts with the effective Kerr background (having spin S_Kerr) through a geodesic-type interaction and an additional spin-dependent interaction proportional to S*. When expanded in post-Newtonian (PN) orders, the EOB Hamiltonian reproduces the leading order spin-spin coupling and the spin-orbit coupling through 2.5PN order, for any mass-ratio. Also, it reproduces all spin-orbit couplings in the test-particle limit. Similarly to the test-particle limit case, when we restrict the EOB dynamics to spins aligned or antialigned with the orbital angular momentum, for which circular orbits exist, the EOB dynamics has several interesting features, such as the existence of an innermost stable circular orbit, a photon circular orbit, and a maximum in the orbital frequency during the plunge subsequent to the inspiral. These properties are crucial for reproducing the dynamics and gravitational-wave emission of spinning black-hole binaries, as calculated in numerical relativity simulations.

abs pdf

Authors: Peter Adshead, Eugene A. Lim

Date: 8 Dec 2009

Abstract: We consider the 3-pt function (i.e. the bispectrum or non-Gaussianity) for stochastic backgrounds of gravitational waves. We estimate the amplitude of this signal for the primordial inflationary background, gravitational waves generated during preheating, and for gravitational waves produced by self-ordering scalar fields following a global phase transition. To assess detectability, we describe how to extract the 3-pt signal from an idealized interferometric experiment and compute the signal to noise ratio as a function of integration time. The 3-pt signal for the stochastic gravitational wave background generated by inflation is unsurprisingly tiny. For gravitational radiation generated by purely causal, classical mechanisms we find that, no matter how non-linear the process is, the 3-pt correlations produced vanish in direct detection experiments. On the other hand, we show that in scenarios where the B-mode of the CMB is sourced by gravitational waves generated by a global phase transition, a strong 3-pt signal among the polarization modes could also be produced. This may provide another method of distinguishing inflationary B-modes. To carry out this computation, we have developed a diagrammatic approach to the calculation of stochastic gravitational waves sourced by scalar fluids, which has applications beyond the present scenario.

abs pdf

Authors: V. Raymond, M.V. van der Sluys, I. Mandel, V. Kalogera, C. Roever, N. Christensen

Date: 18 Dec 2009

Abstract: Gravitational-wave signals from inspirals of binary compact objects (black holes and neutron stars) are primary targets of the ongoing searches by ground-based gravitational-wave (GW) interferometers (LIGO, Virgo, and GEO-600). We present parameter-estimation results from our Markov-chain Monte-Carlo code SPINspiral on signals from binaries with precessing spins. Two data sets are created by injecting simulated GW signals into either synthetic Gaussian noise or into LIGO detector data. We compute the 15-dimensional probability-density functions (PDFs) for both data sets, as well as for a data set containing LIGO data with a known, loud artefact ("glitch"). We show that the analysis of the signal in detector noise yields accuracies similar to those obtained using simulated Gaussian noise. We also find that while the Markov chains from the glitch do not converge, the PDFs would look consistent with a GW signal present in the data. While our parameter-estimation results are encouraging, further investigations into how to differentiate an actual GW signal from noise are necessary.

abs pdf

Authors: P. Delva, J. T. Olympio

Date: 22 Dec 2009

Abstract: In order to do relativistic gravimetry one needs to define a system of null coordinates for a given constellation of satellites. We present here three methods in order to find the null coordinates of an event in a Schwarzschild geometry. We implement these three methods for the weak gravitational field of the Earth, compare their precision and time of computation.

abs pdf

Authors: Matthew D. Duez, Francois Foucart, Lawrence E. Kidder, Christian D. Ott, Saul A. Teukolsky

Date: 17 Dec 2009

Abstract: The merger dynamics of a black hole-neutron star (BHNS) binary is influenced by the neutron star equation of state (EoS) through the latter's effect on the neutron star's radius and on the character of the mass transfer onto the black hole. We study these effects by simulating a number of BHNS binaries in full general relativity using a mixed pseudospectral/finite difference code. We consider several models of the neutron star matter EoS, including Gamma=2 and Gamma=2.75 polytropes and the nuclear-theory based Shen EoS. For models using the Shen EoS, we consider two limits for the evolution of the composition: source-free advection and instantaneous beta-equilibrium. To focus on EoS effects, we fix the mass ratio to 3:1 and the initial aligned black hole spin to a/m=0.5 for all models. We confirm earlier studies which found that more compact stars create a stronger gravitational wave signal but a smaller postmerger accretion disk. We also vary the EoS while holding the compaction fixed. All mergers are qualitatively similar, but we find signatures of the EoS in the waveform and in the tail and disk structures.

abs pdf

Authors: Matthew D. Duez

Date: 17 Dec 2009

Abstract: We review the current status of attempts to numerically model the merger of neutron star-neutron star (NSNS) and black hole-neutron star (BHNS) binary systems, and we describe the understanding of such events that is emerging from these calculations. To accurately model the physics of NSNS and BHNS mergers is a difficult task. It requires solving Einstein's equations for dynamic spacetimes containing black holes. It also requires evolving the hot, supernuclear-density neutron star matter together with the magnetic and radiation fields that can influence the post-merger dynamics. Older studies concentrated on either one or the other of these challenges, but now efforts are being made to model both relativity and microphysics accurately together. These NSNS and BHNS simulations are then used to characterize the gravitational wave signals of such events and to address their potential for generating short-duration gamma ray bursts.

abs pdf

Authors: Walter D. Goldberger, Andreas Ross

Date: 21 Dec 2009

Abstract: In this paper we construct an effective field theory (EFT) that describes long wavelength gravitational radiation from compact systems. To leading order, this EFT consists of the multipole expansion, which we describe in terms of a diffeomorphism invariant point particle Lagrangian. The EFT also systematically captures "post-Minkowskian" corrections to the multipole expansion due to non-linear terms in general relativity. Specifically, we compute long distance corrections from the coupling of the (mass) monopole moment to the quadrupole moment, including up to two mass insertions. Along the way, we encounter both logarithmic short distance (UV) and long wavelength (IR) divergences. We show that the UV divergences can be (1) absorbed into a renormalization of the multipole moments and (2) resummed via the renormalization group. The IR singularities are shown to cancel from properly defined physical observables. As a concrete example of the formalism, we use this EFT to reproduce a number of post-Newtonian corrections to gravitational wave energy flux from non-relativistic binaries, including long distance effects up to 3PN ($vˆ6$) order. Our result verify that the factorization of scales proposed in the NRGR framework of Goldberger and Rothstein is consistent up to order 3PN.

abs pdf

Authors: Michal Was (LAL), Marie-Anne Bizouard (LAL), Violette Brisson (LAL), Fabien Cavalier (LAL), Michel Davier (LAL), Patrice Hello (LAL), Nicolas Leroy (LAL), Florent Robinet (LAL), Vavoulidis Miltiadis (LAL)

Date: 11 Jun 2009

Abstract: Time shifting the outputs of Gravitational Wave detectors operating in coincidence is a convenient way to estimate the background in a search for short duration signals. However this procedure is limited as increasing indefinitely the number of time shifts does not provide better estimates. We show that the false alarm rate estimation error saturates with the number of time shifts. In particular, for detectors with very different trigger rates this error saturates at a large value. Explicit computations are done for 2 detectors, and for 3 detectors where the detection statistic relies on the logical ‘OR’ of the coincidences of the 3 couples in the network.

abs pdf

Authors: N. Andersson, V. Ferrari, D.I. Jones, K.D. Kokkotas, B. Krishnan, J. Read, L. Rezzolla, B. Zink

Date: 2 Dec 2009

Abstract: We discuss different ways that neutron stars can generate gravitational waves, describe recent improvements in modelling the relevant scenarios in the context of improving detector sensitivity, and show how observations are beginning to test our understanding of fundamental physics. The main purpose of the discussion is to establish promising science goals for third-generation ground-based detectors, like the Einstein Telescope, and identify the various challenges that need to be met if we want to use gravitational-wave data to probe neutron star physics.

abs pdf

Authors: Neil Ashby, Bruno Bertotti

Date: 14 Dec 2009

Abstract: This work arose as an aftermath of Cassini's 2002 experiment \cite{bblipt03}, in which the PPN parameter $\gamma$ was measured with an accuracy $\sigma_\gamma = 2.3\times 10ˆ{-5}$ and found consistent with the prediction $\gamma =1$ of general relativity. The Orbit Determination Program (ODP) of NASA's Jet Propulsion Laboratory, which was used in the data analysis, is based on an expression for the gravitational delay which differs from the standard formula; this difference is of second order in powers of $m$ -- the sun's gravitational radius -- but in Cassini's case it was much larger than the expected order of magnitude $mˆ2/b$, where $b$ is the ray's closest approach distance. Since the ODP does not account for any other second-order terms, it is necessary, also in view of future more accurate experiments, to systematically evaluate higher order corrections and to determine which terms are significant. Light propagation in a static spacetime is equivalent to a problem in ordinary geometrical optics; Fermat's action functional at its minimum is just the light-time between the two end points A and B. A new and powerful formulation is thus obtained. Asymptotic power series are necessary to provide a safe and automatic way of selecting which terms to keep at each order. Higher order approximations to the delay and the deflection are obtained. We also show that in a close superior conjunction, when $b$ is much smaller than the distances of A and B from the Sun, of order $R$, say, the second-order correction has an \emph{enhanced} part of order $mˆ2R/bˆ2$, which corresponds just to the second-order terms introduced in the ODP. Gravitational deflection of the image of a far away source, observed from a finite distance from the mass, is obtained to $O(mˆ2)$.

abs pdf

Authors: L. Filipe O. Costa, Carlos A. R. Herdeiro

Date: 11 Dec 2009

Abstract: The similarities between linearized gravity and electromagnetism are known since the early days of General Relativity. Using an exact approach based on tidal tensors, we show that such analogy holds only on very special conditions and depends crucially on the reference frame. This places restrictions on the validity of the "gravito-electromagnetic" equations commonly found in the literature.

abs pdf

Authors: Stuart L. Shapiro

Date: 11 Dec 2009

Abstract: Tidal torques from a binary black hole (BHBH) empty out the central regions in any circumbinary gaseous accretion disk. The balance between tidal torques and viscosity maintain the inner edge of the disk at a radius r ~ 1.5a -- 2a, where a is the binary semimajor axis. Eventually, the inspiraling binary decouples from disk and merges, leaving behind a central hollow ("donut hole") in the disk orbiting the remnant black hole. We present a simple, time-dependent, Newtonian calculation that follows the secular (viscous) evolution of the disk as it fills up the hollow down to the black hole innermost stable circular orbit and then relaxes to stationary equilibrium. We use our model to calculate the electromagnetic radiation ("afterglow") spectrum emitted during this transient accretion epoch. Observing the temporal increase in the total electromagnetic flux and the hardening of the spectrum as the donut hole fills may help confirm a BHBH merger detected by a gravitational wave interferometer. We show how the very existence of the initial hollow can lead to super-Eddington accretion during this secular phase if the rate is not very far below Eddington prior to decoupling. Our model, though highly idealized, may be useful in establishing some of the key parameters, thermal emission features and scalings that characterize this transient. It can serve as a guide in the design and calibration of future radiation-magnetohydrodynamic simulations in general relativity.

abs pdf

Authors: Nicolas Yunes, Frans Pretorius, David Spergel

Date: 15 Dec 2009

Abstract: Space-borne gravitational wave detectors, such as the proposed Laser Interferometer Space Antenna, are expected to observe black hole coalescences to high redshift and with large signal-to-noise ratios, rendering their gravitational waves ideal probes of fundamental physics. The promotion of Newton's constant to a time-function introduces modifications to the binary's binding energy and the gravitational wave luminosity, leading to corrections in the chirping frequency. Such corrections propagate into the response function and, given a gravitational wave observation, they allow for constraints on the first time-derivative of Newton's constant at the time of merger. We find that space-borne detectors could indeed place interesting constraints on this quantity as a function of sky position and redshift, providing a {\emph{constraint map}} over the entire range of redshifts where binary black hole mergers are expected to occur. A LISA observation of an equal-mass inspiral event with total redshifted mass of 10ˆ5 solar masses for three years should be able to measure $\dot{G}/G$ at the time of merger to better than 10ˆ(-11)/yr.

abs pdf

Authors: C. J. Horowitz

Date: 8 Dec 2009

Abstract: Low mass neutron stars may be uniquely strong sources of gravitational waves (GW). The neutron star crust can support large deformations for low mass stars. This is because of the star's weaker gravity. We find maximum ellipticities $\epsilon$ (fractional difference in moments of inertia) that are 1000 times larger, and maximum quadrupole moments $Q_{22}$ over 100 times larger, for low mass stars than for 1.4 $M_\odot$ neutron stars. Indeed, we calculate that the crust can support an $\epsilon$ as large as 0.01 for a minimum mass neutron star. A 0.12 $M_\odot$ star, that is maximally strained and rotating at 100 Hz, will produce a characteristic gravitational wave strain of $h_0=4.2\times 10ˆ{-24}$ at a distance of 1 kpc. The GW detector Advanced LIGO should be sensitive to such objects through out the Milky Way Galaxy.

abs pdf

Authors: Ilya Mandel, Richard O'Shaughnessy

Date: 6 Dec 2009

Abstract: As the ground-based gravitational-wave telescopes LIGO, Virgo, and GEO 600 approach the era of first detections, we review the current knowledge of the coalescence rates and the mass and spin distributions of merging neutron-star and black-hole binaries. We emphasize the bi-directional connection between gravitational-wave astronomy and conventional astrophysics. Astrophysical input will make possible informed decisions about optimal detector configurations and search techniques. Meanwhile, rate upper limits, detected merger rates, and the distribution of masses and spins measured by gravitational-wave searches will constrain astrophysical parameters through comparisons with astrophysical models. Future developments necessary to the success of gravitational-wave astronomy are discussed.

abs pdf

Authors: László Árpád Gergely

Date: 2 Dec 2009

Abstract: We establish the set of independent variables suitable to monitor the complicated evolution of the spinning compact binary during the inspiral. Our approach is valid up to the second post-Newtonian order, including spin and mass quadrupolar effects, for generic (noncircular, nonspherical) orbits. Then we analyze the conservative spin dynamics in terms of these variables. We prove that the only precessing and spinning black hole or neutron star binary configuration which is preserved by the post-Newtonian evolution with spin-spin and quadrupole-monopole contributions included is the equal mass, equal and identically oriented spin configuration. This analytic result puts severe limitations on what particular configurations can be selected in numerical investigations of compact binary evolutions, even in those including only the last orbits of the inspiral.

abs pdf

Authors: A. O. Petters, M. C. Werner

Date: 2 Dec 2009

Abstract: The mathematical theory of gravitational lensing has revealed many generic and global properties. Beginning with multiple imaging, we review Morse-theoretic image counting formulas and lower bound results, and complex-algebraic upper bounds in the case of single and multiple lens planes. We discuss recent advances in the mathematics of stochastic lensing, discussing a general formula for the global expected number of minimum lensed images as well as asymptotic formulas for the probability densities of the microlensing random time delay functions, random lensing maps, and random shear, and an asymptotic expression for the global expected number of micro-minima. Multiple imaging in optical geometry and a spacetime setting are treated. We review global magnification relation results for model-dependent scenarios and cover recent developments on universal local magnification relations for higher order caustics.

abs pdf

Authors: Dimitrios Psaltis (Arizona), Tim Johannsen (Arizona)

Date: 1 Dec 2009

Abstract: The Kerr spacetime of spinning black holes is one of the most intriguing predictions of Einstein's theory of general relativity. The special role this spacetime plays in the theory of gravity is encapsulated in the no-hair theorem, which states that the Kerr metric is the only realistic black-hole solution of the vacuum field equations. Recent and anticipated advances in the observations of black holes throughout the electromagnetic spectrum have secured our understanding of their basic properties while opening up new opportunities for devising tests of the Kerr metric. In this paper, we argue that imaging and spectroscopic observations of accreting black-holes with current and future instruments can lead to the first direct test of the no-hair theorem.

abs pdf

Authors: Robert Dunn (Excellence Cluster "Universe", Munich), Rob Fender (Southampton), Elmar Koerding (Paris), Tomaso Belloni (INAF, Brera), Clement Cabanac (CESR)

Date: 1 Dec 2009

Abstract: (Abridged) We report on a consistent and comprehensive spectral analysis of the X-ray emission of 25 Black Hole X-ray Binaries. All publicly available observations of the black hole binaries in the RXTE archive were analysed. Three different types of model were fitted to investigate the spectral changes occurring during an outburst. For the population, as well as each binary and each outburst from each binary, we construct two diagnostic diagrams. The Hardness Intensity/Luminosity Diagram (HID/HLD) is most useful when studying a single binary. However, to compare between different binary systems, the Disc Fraction Luminosity diagram (DFLD) is more useful. We discuss the limitations of both diagnostic diagrams for the study of the X-ray binary outbursts, and we clearly illustrate how the two diagrams map onto each other for real outburst data. We extract the peak luminosities in a single outburst, as well as the luminosities at the transitions away from- and returning to the powerlaw dominated state for each outburst. The distribution of the luminosities at the transition from the powerlaw to the disc dominated state peaks at around 0.3L_Edd, the same as the peak of the distribution of the peak luminosities in an outburst. Using the disc fraction to calculate the transition luminosities shows that the distributions of the luminosities for the transitions away from- and return to the powerlaw dominated state are both broad and appear to overlap. Finally we compare the measured X-ray luminosities with a small number of contemporaneous radio measurements. Overall this is the most comprehensive and uniform global study of black hole X-ray binaries to date.

abs pdf

Authors: LSST Science Collaborations: Paul A. Abell, Julius Allison, Scott F. Anderson, John R. Andrew, J. Roger P. Angel, Lee Armus, David Arnett, S. J. Asztalos, Tim S. Axelrod, Stephen Bailey, D. R. Ballantyne, Justin R. Bankert, Wayne A. Barkhouse, Jeffrey D. Barr, L. Felipe Barrientos, Aaron J. Barth, James G. Bartlett, Andrew C. Becker, Jacek Becla, Timothy C. Beers, Joseph P. Bernstein, Rahul Biswas, Michael R. Blanton, Joshua S. Bloom, John J. Bochanski, Pat Boeshaar, Kirk D. Borne, Marusa Bradac, W. N. Brandt, Carrie R. Bridge, Michael E. Brown, Robert J. Brunner, James S. Bullock, Adam J. Burgasser, James H. Burge, David L. Burke, Phillip A. Cargile, Srinivasan Chandrasekharan, George Chartas, Steven R. Chesley, You-Hua Chu, David Cinabro, Mark W. Claire, Charles F. Claver, Douglas Clowe, A. J. Connolly, Kem H. Cook, Jeff Cooke, Asantha Cooray, Kevin R. Covey, Christopher S. Culliton, Roelof de Jong, Willem H. de Vries, Victor P. Debattista, Francisco Delgado, Ian P. Dell'Antonio, Saurav Dhital, Rosanne Di Stefano, Mark Dickinson, Benjamin Dilday, S.G. Djorgovski, Gregory Dobler, Ciro Donalek, Gregory Dubois-Felsmann, Josef Durech, Ardis Eliasdottir, Michael Eracleous, Laurent Eyer, Emilio E. Falco, Xiaohui Fan, Christopher D. Fassnacht, Harry C. Ferguson, Yanga R. Fernandez, Brian D. Fields, Douglas Finkbeiner, Eduardo E. Figueroa, Derek B. Fox, Harold Francke, James S. Frank, Josh Frieman, Sebastien Fromenteau, Muhammad Furqan, Gaspar Galaz, A. Gal-Yam, Peter Garnavich, Eric Gawiser, John Geary, Perry Gee, Robert R. Gibson, Kirk Gilmore, Emily A. Grace, Richard F. Green, William J. Gressler, Carl J. Grillmair, Salman Habib, J. S. Haggerty, Mario Hamuy, Alan W. Harris, Suzanne L. Hawley, Alan F. Heavens, Leslie Hebb, Todd J. Henry, Edward Hileman, Eric J. Hilton, Keri Hoadley, J. B. Holberg, Matt J. Holman, Steve B. Howell, Leopoldo Infante, Zeljko Ivezic, Suzanne H. Jacoby, Bhuvnesh Jain, R, Jedicke, M. James Jee, J. Garrett Jernigan, Saurabh W. Jha, Kathryn V. Johnston, R. Lynne Jones, Mario Juric, Mikko Kaasalainen, Styliani (Stella)Kafka, Steven M. Kahn, Nathan A. Kaib, Jason Kalirai, Jeff Kantor, Mansi M. Kasliwal, Charles R. Keeton, Richard Kessler, Zoran Knezevic, Adam Kowalski, Victor L. Krabbendam, K. Simon Krughoff, Shrinivas Kulkarni, Stephen Kuhlman, Mark Lacy, Sebastien Lepine, Ming Liang, Amy Lien, Paulina Lira, Knox S. Long, Suzanne Lorenz, Jennifer M. Lotz, R. H. Lupton, Julie Lutz, Lucas M. Macri, Ashish A. Mahabal, Rachel Mandelbaum, Phil Marshall, Morgan May, Peregrine M. McGehee, Brian T. Meadows, Alan Meert, Andrea Milani, Christopher J. Miller, Michelle Miller, David Mills, Dante Minniti, David Monet, Anjum S. Mukadam, Ehud Nakar, Douglas R. Neill, Jeffrey A. Newman, Sergei Nikolaev, Martin Nordby, Paul O'Connor, Masamune Oguri, John Oliver, Scot S. Olivier, Julia K. Olsen, Knut Olsen, Edward W. Olszewski, Hakeem Oluseyi, Nelson D. Padilla, Alex Parker, Joshua Pepper, John R. Peterson, Catherine Petry, Philip A. Pinto, James L. Pizagno, Bogdan Popescu, Andrej Prsa, Veljko Radcka, M. Jordan Raddick, Andrew Rasmussen, Arne Rau, Jeonghee Rho, James E. Rhoads, Gordon T. Richards, Stephen T. Ridgway, Brant E. Robertson, Rok Roskar, Abhijit Saha, Ata Sarajedini, Evan Scannapieco, Terry Schalk, Rafe Schindler, Samuel Schmidt, Sarah Schmidt, Donald P. Schneider, German Schumacher, Ryan Scranton, Jacques Sebag, Lynn G. Seppala, Ohad Shemmer, Joshua D. Simon, M. Sivertz, Howard A. Smith, J. Allyn Smith, Nathan Smith, Anna H. Spitz, Adam Stanford, Keivan G. Stassun, Jay Strader, Michael A. Strauss, Christopher W. Stubbs, Donald W. Sweeney, Alex Szalay, Paula Szkody, Masahiro Takada, Paul Thorman, David E. Trilling, Virginia Trimble, Anthony Tyson, Richard Van Berg, Daniel Vanden Berk, Jake VanderPlas, Licia Verde, Bojan Vrsnak, Lucianne M. Walkowicz, Benjamin D. Wandelt, Sheng Wang, Yun Wang, Michael Warner, Risa H. Wechsler, Andrew A. West, Oliver Wiecha, Benjamin F. Williams, Beth Willman, David Wittman, Sidney C. Wolff, W. Michael Wood-Vasey, Przemek Wozniak, Patrick Young, Andrew Zentner, Hu Zhan

Date: 1 Dec 2009

Abstract: A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of the exciting science opportunities of the next decade. The Large Synoptic Survey Telescope (LSST) will have an effective aperture of 6.7 meters and an imaging camera with field of view of 9.6 degˆ2, and will be devoted to a ten-year imaging survey over 20,000 degˆ2 south of +15 deg. Each pointing will be imaged 2000 times with fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a total point-source depth of r~27.5. The LSST Science Book describes the basic parameters of the LSST hardware, software, and observing plans. The book discusses educational and outreach opportunities, then goes on to describe a broad range of science that LSST will revolutionize: mapping the inner and outer Solar System, stellar populations in the Milky Way and nearby galaxies, the structure of the Milky Way disk and halo and other objects in the Local Volume, transient and variable objects both at low and high redshift, and the properties of normal and active galaxies at low and high redshift. It then turns to far-field cosmological topics, exploring properties of supernovae to z~1, strong and weak lensing, the large-scale distribution of galaxies and baryon oscillations, and how these different probes may be combined to constrain cosmological models and the physics of dark energy.

abs pdf

Authors: Chris Verhaaren, Eric W. Hirschmann

Date: 30 Nov 2009

Abstract: We consider the orbits of particles with spin in the Schwarzschild spacetime. Using the Papapetrou-Dixon equations of motion for spinning particles, we solve for the orbits and focus on those that exhibit chaos using both Poincaré maps and Lyapunov exponents. In particular, we develop a method for comparing the Lyapunov exponents of chaotic orbits. We find chaotic orbits for smaller spin values than previously thought and with spins that could be realized astrophysically.

abs pdf

Authors: M.Zanolin, S.Vitale, N.Makris

Date: 1 Dec 2009

Abstract: In this paper we describe a new methodology to calculate analytically the error for a maximum likelihood estimate (MLE) for physical parameters from Gravitational wave signals. All the existing litterature focuses on the usage of the Cramer Rao Lower bounds (CRLB) as a mean to approximate the errors for large signal to noise ratios. We show here how the variance and the bias of a MLE estimate can be expressed instead in inverse powers of the signal to noise ratios where the first order in the variance expansion is the CRLB. As an application we compute the second order of the variance and bias for MLE of physical parameters from the inspiral phase of binary mergers and for noises of gravitational wave interferometers . We also compare the improved error estimate with existing numerical estimates. The value of the second order of the variance expansions allows to get error predictions closer to what is observed in numerical simulations. It also predicts correctly the necessary SNR to approximate the error with the CRLB and provides new insight on the relationship between waveform properties SNR and estimation errors. For example the timing match filtering becomes optimal only if the SNR is larger than the kurtosis of the gravitational wave spectrum.

abs pdf

Authors: Tanja Bode, Roland Haas, Tamara Bogdanovic, Pablo Laguna, Deirdre Shoemaker

Date: 1 Dec 2009

Abstract: Coincident detections of electromagnetic (EM) and gravitational wave (GW) signatures from coalescence events of supermassive black holes are the next observational grand challenge. Such detections will provide the means to study cosmological evolution and accretion processes associated with these gargantuan compact objects. More generally, the observations will enable testing general relativity in the strong, nonlinear regime and will provide independent cosmological measurements to high precision. Understanding the conditions under which coincidences of EM and GW signatures arise during supermassive black hole mergers is therefore of paramount importance. As an essential step towards this goal, we present results from the first fully general relativistic, hydrodynamical study of the late inspiral and merger of equal-mass, spinning supermassive black hole binaries in a gas cloud. We find that variable EM signatures correlated with GWs can arise in merging systems as a consequence of shocks and accretion combined with the effect of relativistic beaming. The most striking EM variability is observed for systems where spins are aligned with the orbital axis and where orbiting black holes form a stable set of density wakes, but all systems exhibit some characteristic signatures that can be utilized in searches for EM counterparts. In the case of the most massive binaries observable by the Laser Interferometer Space Antenna, calculated luminosities imply that they may be identified by EM searches to z = 1, while lower mass systems and binaries immersed in low density ambient gas can only be detected in the local universe.

abs pdf