## [1202.4951] Advance of Planetary Perihelion in Post-Newtonian Gravity

Authors: Alexis Larranaga, Luis Cabarique

Date: 22 Feb 2012

Abstract: We present an elementary derivation of the planetary advance of the perihelion for a general spherically symmetric line element in the post- newtonian approximation.

#### Feb 23, 2012

1202.4951 (/preprints)
2012-02-23, 08:46 

## [1202.4202] Two New Tidally Distorted White Dwarfs

Authors: J. J. Hermes, Mukremin Kilic, Warren R. Brown, M. H. Montgomery, D. E. Winget

Date: 20 Feb 2012

Abstract: We identify two new tidally distorted white dwarfs (WDs), SDSS J174140.49+652638.7 and J211921.96-001825.8 (hereafter J1741 and J2119). Both stars are extremely low mass (ELM, < 0.2 Msun) WDs in short-period, detached binary systems. High-speed photometric observations obtained at the McDonald Observatory reveal ellipsoidal variations and Doppler beaming in both systems; J1741, with a minimum companion mass of 1.1 Msun, has one of the strongest Doppler beaming signals ever observed in a binary system (0.59 \pm 0.06% amplitude). We use the observed ellipsoidal variations to constrain the radius of each WD. For J1741, the star's radius must exceed 0.074 Rsun. For J2119, the radius exceeds 0.10 Rsun. These indirect radius measurements are comparable to the radius measurements for the bloated WD companions to A-stars found by the Kepler spacecraft, and they constitute some of the largest radii inferred for any WD. Surprisingly, J1741 also appears to show a 0.23 \pm 0.06% reflection effect, and we discuss possible sources for this excess heating. Both J1741 and J2119 are strong gravitational wave sources, and the time-of-minimum of the ellipsoidal variations can be used to detect the orbital period decay. This may be possible on a timescale of a decade or less.

#### Feb 23, 2012

1202.4202 (/preprints)
2012-02-23, 08:46 

## [1202.4750] Multipole expansion at the level of the action

Authors: Andreas Ross

Date: 21 Feb 2012

Abstract: Sources of long wavelength radiation are naturally described by an effective field theory (EFT) which takes the form of a multipole expansion. Its action is given by a derivative expansion where higher order terms are suppressed by powers of the ratio of the size of the source over the wavelength. In order to determine the Wilson coefficients of the EFT, i.e. the multipole moments, one needs the mapping between a linear source term action and the multipole expansion form of the action of the EFT. In this paper we perform the multipole expansion to all orders by Taylor expanding the field in the source term and then decomposing the action into symmetric trace free tensors which form irreducible representations of the rotation group. We work at the level of the action, and we obtain the action to all orders in the multipole expansion and the exact expressions for the multipole moments for a scalar field, electromagnetism and linearized gravity. Our results for the latter two cases are manifestly gauge invariant. We also give expressions for the energy flux and the (gauge dependent) radiation field to all orders in the multipole expansion. The results for linearized gravity are a component of the EFT framework NRGR and will greatly simplify future calculations of gravitational wave observables in the radiation sector of NRGR.

#### Feb 23, 2012

1202.4750 (/preprints)
2012-02-23, 08:46 

## [1202.4688] Mergers and ejections of black holes in globular clusters

Authors: Sverre Aarseth (IoA, Cambridge)

Date: 21 Feb 2012

Abstract: We report on results of fully consistent N-body simulations of globular cluster models with N = 100 000 members containing neutron stars and black holes. Using the improved ‘algorithmic regularization’ method of Hellstrom and Mikkola for compact subsystems, the new code NBODY7 enables for the first time general relativistic coalescence to be achieved for post-Newtonian terms and realistic parameters. Following an early stage of mass segregation, a few black holes form a small dense core which usually leads to the formation of one dominant binary. The subsequent evolution by dynamical shrinkage involves the competing processes of ejection and mergers by radiation energy loss. Unless the binary is ejected, long-lived triple systems often exhibit Kozai cycles with extremely high inner eccentricity (e > 0.999) which may terminate in coalescence at a few Schwarzschild radii. A characteristic feature is that ordinary stars as well as black holes and even BH binaries are ejected with high velocities. On the basis of the models studied so far, the results suggest a limited growth of a few remaining stellar mass black holes in globular clusters.

#### Feb 23, 2012

1202.4688 (/preprints)
2012-02-23, 08:46 

## [1202.4031] Prospects for early localization of gravitational-wave signals from compact binary coalescences with advanced detectors

Authors: Alessandro Manzotti, Alexander Dietz

Date: 17 Feb 2012

Abstract: A leading candidate source of detectable gravitational waves is the inspiral and merger of pairs of stellar-mass compact objects. The advanced LIGO and advanced Virgo detectors will allow scientists to detect inspiral signals from more massive systems and at earlier times in the detector band, than with first generation detectors. The signal from a coalescence of two neutron stars is expected to stay in the sensitive band of advanced detectors for several minutes, thus allowing detection before the final coalescence of the system. In this work, the prospects of detecting inspiral signals prior to coalescence, and the possibility to derive a suitable sky area for source locations are investigated. As a large fraction of the signal is accumulated in the last ~10 seconds prior to coalescence, bandwidth and timing accuracy are largely accrued in the very last moments prior to coalescence. We use Monte Carlo techniques to estimate the accuracy of sky localization through networks of ground-based interferometers such as aLIGO and aVirgo. With the addition of the Japanese KAGRA detector, it is shown that the detection and triangulation before coalescence may be feasible.

#### Feb 23, 2012

1202.4031 (/preprints)
2012-02-23, 08:45 

## [1202.3565] Effective action approach to higher-order relativistic tidal interactions in binary systems and their effective one body description

Authors: Donato Bini, Thibault Damour, Guillaume Faye

Date: 16 Feb 2012

Abstract: The gravitational-wave signal from inspiralling neutron-star--neutron-star (or black-hole--neutron-star) binaries will be influenced by tidal coupling in the system. An important science goal in the gravitational-wave detection of these systems is to obtain information about the equation of state of neutron star matter via the measurement of the tidal polarizability parameters of neutron stars. To extract this piece of information will require to have accurate analytical descriptions of both the motion and the radiation of tidally interacting binaries. We improve the analytical description of the late inspiral dynamics by computing the next-to-next-to-leading order relativistic correction to the tidal interaction energy. Our calculation is based on an effective-action approach to tidal interactions, and on its transcription within the effective-one-body formalism. We find that second-order relativistic effects (quadratic in the relativistic gravitational potential $u=G(m_1 +m_2)/(cˆ2 r)$) significantly increase the effective tidal polarizability of neutron stars by a distance-dependent amplification factor of the form $1 + \alpha_1 \, u + \alpha_2 \, uˆ2 +…$ where, say for an equal-mass binary, $\alpha_1=5/4=1.25$ (as previously known) and $\alpha_2=85/14\simeq6.07143$ (as determined here for the first time). We argue that higher-order relativistic effects will lead to further amplification, and we suggest a Padé-type way of resumming them. We recommend to test our results by comparing resolution-extrapolated numerical simulations of inspiralling-binary neutron stars to their effective one body description.

#### Feb 23, 2012

1202.3565 (/preprints)
2012-02-23, 08:45 

## [1202.3512] Gravitational wave observations of galactic intermediate-mass black hole binaries with DECIGO Path Finder

Authors: Kent Yagi

Date: 16 Feb 2012

Abstract: DECIGO Path Finder (DPF) is a space-borne gravitational wave (GW) detector with sensitivity in the frequency band 0.1--100Hz. As a first step mission to DECIGO, it is aiming for launching in 2016--2017. Although its main objective is to demonstrate technology for GW observation in space, DPF still has a chance of detecting GW signals and performing astrophysical observations. With an observable range up to 50 kpc, its main targets are GW signals from galactic intermediate mass black hole (IMBH) binaries. By using inspiral-merger-ringdown phenomenological waveforms, we perform both pattern-averaged analysis and Monte Carlo simulations including the effect of detector motion to find that the masses and (effective) spins of the IMBHs could be determined with errors of a few percent, should the signals be detected. Since GW signals from IMBH binaries with masses above $10ˆ4 M_\odot$ cannot be detected by ground-based detectors, these objects can be unique sources for DPF. If the inspiral signal of a $10ˆ3M_\odot$ IMBH binary is detected with DPF, it can give alert to the ringdown signal for the ground-based detectors $10ˆ2$--$10ˆ3$s before coalescence. We also estimate the possible bound on the graviton Compton wavelength from a possible IMBH binary in $\omega$ Centauri. We obtain a slightly weaker constraint than the solar system experiment and an about 2 orders of magnitude stronger constraint than the one from binary pulsar tests. Unfortunately, the detection rate of IMBH binaries is rather small.

#### Feb 23, 2012

1202.3512 (/preprints)
2012-02-23, 08:45 

## [1202.3990] A Bayesian Approach to Calibrating Period-Luminosity Relations of RR Lyrae Stars in the Mid-Infrared

Authors: Christopher R. Klein, Joseph W. Richards, Nathaniel R. Butler, Joshua S. Bloom

Date: 17 Feb 2012

Abstract: A Bayesian approach to calibrating period-luminosity (PL) relations has substantial benefits over generic least-squares fits. In particular, the Bayesian approach takes into account the full prior distribution of the model parameters, such as the a priori distances, and refits these parameters as part of the process of settling on the most highly-constrained final fit. Additionally, the Bayesian approach can naturally ingest data from multiple wavebands and simultaneously fit the parameters of PL relations for each waveband in a procedure that constrains the parameter posterior distributions so as to minimize the scatter of the final fits appropriately in all wavebands. Here we describe the generalized approach to Bayesian model fitting and then specialize to a detailed description of applying Bayesian linear model fitting to the mid-infrared PL relations of RR Lyrae variable stars. For this example application we quantify the improvement afforded by using a Bayesian model fit. We also compare distances previously predicted in our example application to recently published parallax distances measured with the Hubble Space Telescope and find their agreement to be a vindication of our methodology. Our intent with this article is to spread awareness of the benefits and applicability of this Bayesian approach and encourage future PL relation investigations to consider employing this powerful analysis method.

#### Feb 23, 2012

1202.3990 (/preprints)
2012-02-23, 08:45 

## [1202.3595] Detecting Cosmic Gravitational-wave Background from Super-heavy Cosmic Strings with LISA

Authors: Alf Tang, Timothy J. Sumner

Date: 16 Feb 2012

Abstract: Although cosmic string scenario for galaxy formation is disfavored by CMB data, it is of great interest in the generation of cosmic gravitational-wave background. This research aims to develop an algorithm to extract cosmic gravitational-wave background produced by cosmic strings from the LISA data stream, and apply the algorithm to the simulated data stream containing the background produced by cosmic strings with various strength to study the detection threshold for this source. For 1-yr observation, It is found that the detection threshold of G{\mu} is 3.12 \times 10ˆ-16 in the standard scenario. In the case that p and {\epsilon} are adjustable, the detectable region in parameter space is defined by (G{\mu})ˆ2/3 {\epsilon}ˆ-1/3 / p> 4.6 \times 10-11.

#### Feb 23, 2012

1202.3595 (/preprints)
2012-02-23, 08:45 

## [1202.4893] Black hole perturbation in the most general scalar-tensor theory with second-order field equations I: the odd-parity sector

Authors: Tsutomu Kobayashi, Hayato Motohashi, Teruaki Suyama

Date: 22 Feb 2012

Abstract: We perform a fully relativistic analysis of odd-type linear perturbations around a static and spherically symmetric solution in the most general scalar-tensor theory with second-order field equations. It is shown that, as in the case of general relativity, the quadratic action for the perturbations reduces to the one having only a single dynamical variable, from which concise formulas for no-ghost and no-gradient instability conditions are derived. Our result is applicable to all the theories of gravity with an extra scalar degree of freedom. We demonstrate how the generic formulas can be applied to some particular examples such as the Brans-Dicke theory, $f(R)$ models, and Galileon gravity.

#### Feb 23, 2012

1202.4893 (/preprints)
2012-02-23, 08:39 

## [1202.2179] The Swift short gamma-ray burst rate density: implications for binary neutron star merger rates

Authors: David Coward, Eric Howell, Tsvi Piran, Giulia Stratta, Marica Branchesi, Omer Bromberg, Bruce Gendre, Ronald Burman, Dafne Guetta

Date: 10 Feb 2012

Abstract: Short gamma-ray bursts (SGRBs) observed by {\it Swift} are potentially revealing the first insight into cataclysmic compact object mergers. To ultimately acquire a fundamental understanding of these events requires pan-spectral observations and knowledge of their spatial distribution to differentiate between proposed progenitor populations. Presently (late 2011) there are only some 30% of SGRBs with reasonably firm redshifts, and this sample is highly biased by the limited sensitivity of {\it Swift} to detect SGRBs. We account for the dominant biases to calculate a realistic SGRB rate density out to $z\approx0.5$ using the {\it Swift} sample of peak fluxes, redshifts, and those SGRBs with a beaming angle constraint from X-ray/optical observations. We find an SGRB lower rate density of $7.1ˆ{+4.9}_{-3.2}$ $\mathrm{Gpc}ˆ{-3}\mathrm{yr}ˆ{-1}$ (assuming isotropic emission), and a beaming corrected upper limit of $1200ˆ{+840}_{-550}$ $\mathrm{Gpc}ˆ{-3}\mathrm{yr}ˆ{-1}$. Assuming a significant fraction of binary neutron star mergers produce SGRBs, we calculate lower and upper detection rate limits of $(1-200)$ yr$ˆ{-1}$ by an ALIGO and Virgo coincidence search. Our detection rate is similar to the lower and realistic rates inferred from extrapolations using Galactic pulsar observations and population synthesis.

#### Feb 12, 2012

1202.2179 (/preprints)
2012-02-12, 23:17 

## [1202.1986] Perturbations in Massive Gravity Cosmology

Authors: Marco Crisostomi, Denis Comelli, Luigi Pilo

Date: 9 Feb 2012

Abstract: We study cosmological perturbations for a ghost free massive gravity theory formulated with a dynamical extra metric that is needed to massive deform GR. In this formulation FRW background solutions fall in two branches. In the dynamics of perturbations around the first branch solutions, no extra degree of freedom with respect to GR ispresent at linearized level, likewise what is found in the Stuckelberg formulation of massive gravity where the extra metric isflat and non dynamical. In the first branch, perturbations are probably strongly coupled. On the contrary, for perturbations around the second branch solutions all expected degrees of freedom propagate. While tensor and vector perturbations of the physical metric that couples with matter follow closely the ones of GR, scalars develop an exponential Jeans-like instability on sub-horizon scales. On the other hand, around a de Sitter background there is no instability. We argue that one could get rid of the instabilities by introducing a mirror dark matter sector minimally coupled to only the second metric.

#### Feb 09, 2012

1202.1986 (/preprints)
2012-02-09, 20:42 

## [1202.1977] Recoiling black holes: electromagnetic signatures, candidates, and astrophysical implications

Authors: S. Komossa (TUM/ExCU/IPP)

Date: 9 Feb 2012

Abstract: Supermassive black holes (SMBHs) may not always reside right at the centers of their host galaxies. This is a prediction of numerical relativity simulations, which imply that the newly formed single SMBH, after binary coalescence in a galaxy merger, can receive kick velocities up to several 1000 km/s due to anisotropic emission of gravitational waves. Long-lived oscillations of the SMBHs in galaxy cores, and in rare cases even SMBH ejections from their host galaxies, are the consequence. Observationally, accreting recoiling SMBHs would appear as quasars spatially and/or kinematically off-set from their host galaxies. The presence of the "kicks" has a wide range of astrophysical implications which only now are beginning to be explored, including consequences for black hole and galaxy assembly at the epoch of structure formation, black hole feeding, and unified models of Active Galactic Nuclei (AGN). Here, we review the observational signatures of recoiling SMBHs and the properties of the first candidates which have emerged, including follow-up studies of the candidate recoiling SMBH of SDSSJ092712.65+294344.0.

#### Feb 09, 2012

1202.1977 (/preprints)
2012-02-09, 20:42 

## [1202.0839] Low-frequency gravitational-wave science with eLISA/NGO

Authors: Pau Amaro-Seoane, Sofiane Aoudia, Stanislav Babak, Pierre Binetruy, Emanuele Berti, Alejandro Bohe, Chiara Caprini, Monica Colpi, Neil J. Cornish, Karsten Danzmann, Jean-Francois Dufaux, Jonathan Gair, Oliver Jennrich, Philippe Jetzer, Antoine Klein, Ryan N. Lang, Alberto Lobo, Tyson Littenberg, Sean T. McWilliams, Gijs Nelemans, Antoine Petiteau, Edward K. Porter, Bernard F. Schutz, Alberto Sesana, Robin Stebbins, Tim Sumner, Michele Vallisneri, Stefano Vitale, Marta Volonteri, Henry Ward

Date: 3 Feb 2012

Abstract: We review the expected science performance of the New Gravitational-Wave Observatory (NGO, a.k.a. eLISA), a mission under study by the European Space Agency for launch in the early 2020s. eLISA will survey the low-frequency gravitational-wave sky (from 0.1 mHz to 1 Hz), detecting and characterizing a broad variety of systems and events throughout the Universe, including the coalescences of massive black holes brought together by galaxy mergers; the inspirals of stellar-mass black holes and compact stars into central galactic black holes; several millions of ultracompact binaries, both detached and mass transferring, in the Galaxy; and possibly unforeseen sources such as the relic gravitational-wave radiation from the early Universe. eLISA's high signal-to-noise measurements will provide new insight into the structure and history of the Universe, and they will test general relativity in its strong-field dynamical regime.

#### Feb 07, 2012

1202.0839 (/preprints)
2012-02-07, 12:01 

## [1202.0790] A prototype effective-one-body model for non-precessing spinning inspiral-merger-ringdown waveforms

Authors: Andrea Taracchini, Yi Pan, Alessandra Buonanno, Enrico Barausse, Michael Boyle, Tony Chu, Geoffrey Lovelace, Harald P. Pfeiffer, Mark A. Scheel

Date: 3 Feb 2012

Abstract: We first use five non-spinning and two mildly spinning (chi_i \simeq -0.44, +0.44) numerical-relativity waveforms of black-hole binaries and calibrate an effective-one-body (EOB) model for non-precessing spinning binaries, notably its dynamics and the dominant (2,2) gravitational-wave mode. Then, we combine the above results with recent outcomes of small-mass-ratio simulations produced by the Teukolsky equation and build a prototype EOB model for detection purposes, which is capable of generating inspiral-merger-ringdown waveforms for non-precessing spinning black-hole binaries with any mass ratio and individual black-hole spins -1 \leq chi_i \lesssim 0.7. We compare the prototype EOB model to two equal-mass highly spinning numerical-relativity waveforms of black holes with spins chi_i = -0.95, +0.97, which were not available at the time the EOB model was calibrated. In the case of Advanced LIGO we find that the mismatch between prototype-EOB and numerical-relativity waveforms is always smaller than 0.003 for total mass 20-200 M_\odot, the mismatch being computed by maximizing only over the initial phase and time. To successfully generate merger waveforms for individual black-hole spins chi_i \gtrsim 0.7, the prototype-EOB model needs to be improved by (i) better modeling the plunge dynamics and (ii) including higher-order PN spin terms in the gravitational-wave modes and radiation-reaction force.

#### Feb 05, 2012

1202.0790 (/preprints)
2012-02-05, 22:35 

## [1202.0808] Practical Methods for Continuous Gravitational Wave Detection using Pulsar Timing Data

Authors: J. A. Ellis, F. A. Jenet, M. A. McLaughlin

Date: 3 Feb 2012

Abstract: Gravitational Waves (GWs) are tiny ripples in the fabric of space-time predicted by Einstein's General Relativity. Pulsar timing arrays (PTAs) are well poised to detect low frequency ($10ˆ{-9}$ -- $10ˆ{-7}$ Hz) GWs in the near future. There has been a significant amount of research into the detection of a stochastic background of GWs from supermassive black hole binaries (SMBHBs). Recent work has shown that single continuous sources standing out above the background may be detectable by PTAs operating at a sensitivity sufficient to detect the stochastic background. The most likely sources of continuous GWs in the pulsar timing frequency band are extremely massive and/or nearby SMBHBs. In this paper we present detection strategies including various forms of matched filtering and power spectral summing. We determine the efficacy and computational cost of such strategies. It is shown that it is computationally infeasible to use an optimal matched filter including the poorly constrained pulsar distances with a grid based method. We show that an Earth-term-matched filter constructed using only the correlated signal terms is both computationally viable and highly sensitive to GW signals. This technique is only a factor of two less sensitive than the computationally unrealizable optimal matched filter and a factor of two more sensitive than a power spectral summing technique. We further show that a pairwise matched filter, taking the pulsar distances into account is comparable to the optimal matched filter for the single template case and comparable to the Earth-term-matched filter for many search templates. Finally, using simulated data optimal quality, we place a theoretical minimum detectable strain amplitude of $h>2\times 10ˆ{-15}$ from continuous GWs at frequencies on the order $\sim1/T_{\rm obs}$.

#### Feb 05, 2012

1202.0808 (/preprints)
2012-02-05, 22:35 

## [1202.0804] Compact object coalescence rate estimation from short gamma-ray burst observations

Authors: Carlo Enrico Petrillo, Alexander Dietz

Date: 3 Feb 2012

Abstract: Recent observational and theoretical work increase the confidence that short-duration gamma-ray bursts are created by the coalescence of compact objects, like neutron stars and/or black holes. From the observation of short-duration gamma-ray bursts with know distances it is possible to infer their rate in the local universe, and draw conclusions for the rate of compact binary coalescences. Although the sample of such events with reliable redshift measurements is very small, we try to model the distribution with a luminosity function and a rate function. The analysis performed with a sample of 15 short gamma-ray bursts yields a range for the merger rate of 75 to 660 Gpc$ˆ{-3}$yr$ˆ{-1}$, with a median rate of 180 Gpc$ˆ{-3}$yr$ˆ{-1}$. This result is in general agreement with similar investigations using gamma-ray burst observations. Furthermore, we estimate the number of coincident observations of gravitational wave signals with short gamma-ray bursts in the advanced detector era. Assuming each short gamma-ray burst is created by a double neutron star merger, the expected rate of coincident observations is 0.1 to 1.1 per year, when assuming each short gamma-ray burst is created by a merger of a neutron star and a black hole, this rate becomes 0.4 to 4.0 per year.

#### Feb 05, 2012

1202.0804 (/preprints)
2012-02-05, 22:35 

## [1202.0394] Black holes and stellar structures in f(R)-gravity

Authors: M. De Laurentis, S. Capozziello

Date: 2 Feb 2012

Abstract: We review black hole solutions and self-gravitating structures in f(R)-gravity.

#### Feb 02, 2012

1202.0394 (/preprints)
2012-02-02, 18:22 

## [1201.5319] The NINJA-2 catalog of hybrid post-Newtonian/numerical-relativity waveforms for non-precessing black-hole binaries

Authors: P. Ajith, Michael Boyle, Duncan A. Brown, Bernd Br&#xfc;gmann, Luisa T. Buchman, Laura Cadonati, Manuela Campanelli, Tony Chu, Zachariah B. Etienne, Stephen Fairhurst, Mark Hannam, James Healy, Ian Hinder, Sascha Husa, Lawrence E. Kidder, Badri Krishnan, Pablo Laguna, Yuk Tung Liu, Lionel London, Carlos O. Lousto, Geoffrey Lovelace, Ilana MacDonald, Pedro Marronetti, Satya Mohapatra, Philipp M&#xf6;sta, Doreen M&#xfc;ller, Bruno C. Mundim, Hiroyuki Nakano, Frank Ohme, Vasileios Paschalidis, Larne Pekowsky, Denis Pollney, Harald P. Pfeiffer, Marcelo Ponce, Michael P&#xfc;rrer, George Reifenberger, Christian Reisswig, Luc&#xed;a Santamar&#xed;a, Mark A. Scheel, Stuart L. Shapiro, Deirdre Shoemaker, Carlos F. Sopuerta, Ulrich Sperhake, B&#xe9;la Szil&#xe1;gyi, Nicholas W. Taylor, Wolfgang Tichy, Petr Tsatsin, Yosef Zlochower

Date: 25 Jan 2012

Abstract: The Numerical INJection Analysis (NINJA) project is a collaborative effort between members of the numerical relativity and gravitational wave data analysis communities. The purpose of NINJA is to study the sensitivity of existing gravitational-wave search and parameter-estimation algorithms using numerically generated waveforms, and to foster closer collaboration between the numerical relativity and data analysis communities. The first NINJA project used only a small number of injections of short numerical-relativity waveforms, which limited its ability to draw quantitative conclusions. The goal of the NINJA-2 project is to overcome these limitations with long post-Newtonian - numerical relativity hybrid waveforms, large numbers of injections, and the use of real detector data. We report on the submission requirements for the NINJA-2 project and the construction of the waveform catalog. Eight numerical relativity groups have contributed 63 hybrid waveforms consisting of a numerical portion modelling the late inspiral, merger, and ringdown stitched to a post-Newtonian portion modelling the early inspiral. We summarize the techniques used by each group in constructing their submissions. We also report on the procedures used to validate these submissions, including examination in the time and frequency domains and comparisons of waveforms from different groups against each other. These procedures have so far considered only the $(\ell,m)=(2,2)$ mode. Based on these studies we judge that the hybrid waveforms are suitable for NINJA-2 studies. We note some of the plans for these investigations.

#### Feb 02, 2012

1201.5319 (/preprints)
2012-02-02, 16:16 

## [1201.5244] An F-statistic based multi-detector veto for detector artifacts in continuous-wave gravitational wave data

Authors: David Keitel, Reinhard Prix, Maria Alessandra Papa, Maham Siddiqi

Date: 25 Jan 2012

Abstract: Continuous gravitational waves (CW) are expected from spinning neutron stars with non-axisymmetric deformations. A network of interferometric detectors (LIGO, Virgo and GEO600) is looking for these signals. They are predicted to be very weak and retrievable only by integration over long observation times. One of the standard methods of CW data analysis is the multi-detector F-statistic. In a typical search, the F-statistic is computed over a range in frequency, spin-down and sky position, and the candidates with highest F values are kept for further analysis. However, this detection statistic is susceptible to a class of noise artifacts, strong monochromatic lines in a single detector. By assuming an extended noise model - standard Gaussian noise plus single-detector lines - we can use a Bayesian odds ratio to derive a generalized detection statistic, the line veto (LV-) statistic. In the absence of lines, it behaves similarly to the F-statistic, but it is more robust against line artifacts. In the past, ad-hoc post-processing vetoes have been implemented in searches to remove these artifacts. Here we provide a systematic framework to develop and benchmark this class of vetoes. We present our results from testing this LV-statistic on simulated data.

#### Feb 02, 2012

1201.5244 (/preprints)
2012-02-02, 16:15 

## [1201.5599] Performance of an externally triggered gravitational-wave burst search

Authors: Michal Was, Patrick J. Sutton, Gareth Jones, Isabel Leonor

Date: 26 Jan 2012

Abstract: We present the performance of searches for gravitational wave bursts associated with external astrophysical triggers as a function of the search sky region. We discuss both the case of Gaussian noise and real noise of gravitational wave detectors for arbitrary detector networks. We demonstrate the ability to reach Gaussian limited sensitivity in real non-Gaussian data, and show the conditions required to attain it. We find that a single sky position search is ~20% more sensitive than an all-sky search of the same data.

#### Feb 02, 2012

1201.5599 (/preprints)
2012-02-02, 16:15 

## [1201.5888] The evolution of massive black holes and their spins in their galactic hosts

Authors: Enrico Barausse

Date: 27 Jan 2012

Abstract: [Abridged] […] In this paper, we study the mass and spin evolution of massive black holes within a semianalytical galaxy-formation model that follows the evolution of dark-matter halos along merger trees, as well as that of the baryonic components (hot gas, stellar and gaseous bulges, and stellar and gaseous galactic disks). This allows us to study the mass and spin evolution of massive black holes in a self-consistent way, by taking into account the effect of the gas present in galactic nuclei both during the accretion phases and during mergers. Also, we present predictions, as a function of redshift, for the fraction of gas-rich black-hole mergers -- in which the spins prior to the merger are aligned due to the gravito-magnetic torques exerted by the circumbinary disk -- as opposed to gas-poor mergers, in which the orientation of the spins before the merger is roughly isotropic. These predictions may be tested by LISA or similar spaced-based gravitational-wave detectors such as eLISA/NGO or SGO.

#### Feb 02, 2012

1201.5888 (/preprints)
2012-02-02, 16:14 

## [1201.5715] Approximate Waveforms for Extreme-Mass-Ratio Inspirals: The Chimera Scheme

Authors: Carlos F. Sopuerta, Nicolas Yunes

Date: 27 Jan 2012

Abstract: We describe a new kludge scheme to model the dynamics of generic extreme-mass-ratio inspirals (EMRIs; stellar compact objects spiraling into a spinning supermassive black hole) and their gravitational-wave emission. The Chimera scheme is a hybrid method that combines tools from different approximation techniques in General Relativity: (i) A multipolar, post-Minkowskian expansion for the far-zone metric perturbation (the gravitational waveforms) and for the local prescription of the self-force; (ii) a post-Newtonian expansion for the computation of the multipole moments in terms of the trajectories; and (iii) a BH perturbation theory expansion when treating the trajectories as a sequence of self-adjusting Kerr geodesics. The EMRI trajectory is made out of Kerr geodesic fragments joined via the method of osculating elements as dictated by the multipolar post-Minkowskian radiation-reaction prescription. We implemented the proper coordinate mapping between Boyer-Lindquist coordinates, associated with the Kerr geodesics, and harmonic coordinates, associated with the multipolar post-Minkowskian decomposition. The Chimera scheme is thus a combination of approximations that can be used to model generic inspirals of systems with extreme to intermediate mass ratios, and hence, it can provide valuable information for future space-based gravitational-wave observatories, like LISA, and even for advanced ground detectors. The local character in time of our multipolar post-Minkowskian self-force makes this scheme amenable to study the possible appearance of transient resonances in generic inspirals.

#### Feb 02, 2012

1201.5715 (/preprints)
2012-02-02, 16:13 

## [1201.5656] Comparison of Atom Interferometers and Light Interferometers as Space-Based Gravitational Wave Detectors

Authors: John G. Baker, James Ira Thorpe

Date: 26 Jan 2012

Abstract: We consider a class of proposed gravitational wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, non-inertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g. multiple arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe.

#### Feb 02, 2012

1201.5656 (/preprints)
2012-02-02, 16:13 

## [1201.5999] Search for Gravitational Waves from Intermediate Mass Binary Black Holes

Date: 28 Jan 2012

Abstract: We present the results of a weakly modeled burst search for gravitational waves from mergers of non-spinning intermediate mass black holes (IMBH) in the total mass range 100--450 solar masses and with the component mass ratios between 1:1 and 4:1. The search was conducted on data collected by the LIGO and Virgo detectors between November of 2005 and October of 2007. No plausible signals were observed by the search which constrains the astrophysical rates of the IMBH mergers as a function of the component masses. In the most efficiently detected bin centered on 88+88 solar masses, for non-spinning sources, the rate density upper limit is 0.13 per Mpcˆ3 per Myr at the 90% confidence level.

#### Feb 02, 2012

1201.5999 (/preprints)
2012-02-02, 16:11