http://www.vallis.org/blogspace My Experimental Blosxom Weblog. en http://www.vallis.org/blogspace/2012/02/05#1202.0790 <p class="story_para"> <b>Authors</b>: Andrea Taracchini, Yi Pan, Alessandra Buonanno, Enrico Barausse, Michael Boyle, Tony Chu, Geoffrey Lovelace, Harald P. Pfeiffer, Mark A. Scheel </p> <p class="story_para"> <b>Date</b>: 3 Feb 2012 </p> <p class="story_para"> <b>Abstract</b>: 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. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1202.0790">abs</a> <a href="http://www.arxiv.org/pdf/1202.0790">pdf</a></p> http://www.vallis.org/blogspace/2012/02/05#1202.0808 <p class="story_para"> <b>Authors</b>: J. A. Ellis, F. A. Jenet, M. A. McLaughlin </p> <p class="story_para"> <b>Date</b>: 3 Feb 2012 </p> <p class="story_para"> <b>Abstract</b>: 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 ($10&circ;{-9}$ -- $10&circ;{-7}$ 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 $h&gt;2\times 10&circ;{-15}$ from continuous GWs at frequencies on the order $\sim1/T_{\rm obs}$. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1202.0808">abs</a> <a href="http://www.arxiv.org/pdf/1202.0808">pdf</a></p> http://www.vallis.org/blogspace/2012/02/05#1202.0804 <p class="story_para"> <b>Authors</b>: Carlo Enrico Petrillo, Alexander Dietz </p> <p class="story_para"> <b>Date</b>: 3 Feb 2012 </p> <p class="story_para"> <b>Abstract</b>: 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$&circ;{-3}$yr$&circ;{-1}$, with a median rate of 180 Gpc$&circ;{-3}$yr$&circ;{-1}$. 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. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1202.0804">abs</a> <a href="http://www.arxiv.org/pdf/1202.0804">pdf</a></p> http://www.vallis.org/blogspace/2012/02/02#1202.0394 <p class="story_para"> <b>Authors</b>: M. De Laurentis, S. Capozziello </p> <p class="story_para"> <b>Date</b>: 2 Feb 2012 </p> <p class="story_para"> <b>Abstract</b>: We review black hole solutions and self-gravitating structures in f(R)-gravity. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1202.0394">abs</a> <a href="http://www.arxiv.org/pdf/1202.0394">pdf</a></p> http://www.vallis.org/blogspace/2012/02/02#1201.5319 <p class="story_para"> <b>Authors</b>: P. Ajith, Michael Boyle, Duncan A. Brown, Bernd Br&amp;#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&amp;#xf6;sta, Doreen M&amp;#xfc;ller, Bruno C. Mundim, Hiroyuki Nakano, Frank Ohme, Vasileios Paschalidis, Larne Pekowsky, Denis Pollney, Harald P. Pfeiffer, Marcelo Ponce, Michael P&amp;#xfc;rrer, George Reifenberger, Christian Reisswig, Luc&amp;#xed;a Santamar&amp;#xed;a, Mark A. Scheel, Stuart L. Shapiro, Deirdre Shoemaker, Carlos F. Sopuerta, Ulrich Sperhake, B&amp;#xe9;la Szil&amp;#xe1;gyi, Nicholas W. Taylor, Wolfgang Tichy, Petr Tsatsin, Yosef Zlochower </p> <p class="story_para"> <b>Date</b>: 25 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: 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. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.5319">abs</a> <a href="http://www.arxiv.org/pdf/1201.5319">pdf</a></p> http://www.vallis.org/blogspace/2012/02/02#1201.5244 <p class="story_para"> <b>Authors</b>: David Keitel, Reinhard Prix, Maria Alessandra Papa, Maham Siddiqi </p> <p class="story_para"> <b>Date</b>: 25 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: 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. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.5244">abs</a> <a href="http://www.arxiv.org/pdf/1201.5244">pdf</a></p> http://www.vallis.org/blogspace/2012/02/02#1201.5599 <p class="story_para"> <b>Authors</b>: Michal Was, Patrick J. Sutton, Gareth Jones, Isabel Leonor </p> <p class="story_para"> <b>Date</b>: 26 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: 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. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.5599">abs</a> <a href="http://www.arxiv.org/pdf/1201.5599">pdf</a></p> http://www.vallis.org/blogspace/2012/02/02#1201.5888 <p class="story_para"> <b>Authors</b>: Enrico Barausse </p> <p class="story_para"> <b>Date</b>: 27 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: [Abridged] [&hellip;] 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. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.5888">abs</a> <a href="http://www.arxiv.org/pdf/1201.5888">pdf</a></p> http://www.vallis.org/blogspace/2012/02/02#1201.5715 <p class="story_para"> <b>Authors</b>: Carlos F. Sopuerta, Nicolas Yunes </p> <p class="story_para"> <b>Date</b>: 27 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: 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. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.5715">abs</a> <a href="http://www.arxiv.org/pdf/1201.5715">pdf</a></p> http://www.vallis.org/blogspace/2012/02/02#1201.5656 <p class="story_para"> <b>Authors</b>: John G. Baker, James Ira Thorpe </p> <p class="story_para"> <b>Date</b>: 26 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: 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. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.5656">abs</a> <a href="http://www.arxiv.org/pdf/1201.5656">pdf</a></p> http://www.vallis.org/blogspace/2012/02/02#1201.5999 <p class="story_para"> <b>Authors</b>: J. Abadie et al.* </p> <p class="story_para"> <b>Date</b>: 28 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: 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 Mpc&circ;3 per Myr at the 90% confidence level. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.5999">abs</a> <a href="http://www.arxiv.org/pdf/1201.5999">pdf</a></p> http://www.vallis.org/blogspace/2012/01/25#1201.5089 <p class="story_para"> <b>Authors</b>: Adam Pound </p> <p class="story_para"> <b>Date</b>: 24 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: Using a rigorous method of matched asymptotic expansions, I derive the equation of motion of a small, compact body in an external vacuum spacetime through second order in the body's mass (neglecting effects of internal structure). The motion is found to be geodesic in a certain locally defined regular geometry satisfying Einstein's equation at second order. I provide a practical scheme for numerically obtaining both the metric of that regular geometry and the complete second-order metric perturbation produced by the body. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.5089">abs</a> <a href="http://www.arxiv.org/pdf/1201.5089">pdf</a></p> http://www.vallis.org/blogspace/2012/01/25#1201.4873 <p class="story_para"> <b>Authors</b>: Evghenii Gaburov, Anders Johansen, Yuri Levin </p> <p class="story_para"> <b>Date</b>: 23 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: In this paper we report on the formation of magnetically-levitating accretion disks around supermassive black holes. The structure of these disks is calculated by numerically modelling tidal disruption of magnetized interstellar gas clouds. We find that the resulting disks are entirely supported by the pressure of the magnetic fields against the component of gravitational force directed perpendicular to the disks. The magnetic field shows ordered large-scale geometry that remains stable for the duration of our numerical experiments extending over 10% of the disk lifetime. Strong magnetic pressure allows high accretion and inhibits disk fragmentation. This in combination with the repeated feeding of manetized molecular clouds to a supermassive black hole yields a possible solution to the long-standing puzzle of black hole growth in the centres of galaxies. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.4873">abs</a> <a href="http://www.arxiv.org/pdf/1201.4873">pdf</a></p> http://www.vallis.org/blogspace/2012/01/25#1201.5041 <p class="story_para"> <b>Authors</b>: A. Hees, B. Lamine, S. Reynaud, M.-T. Jaekel, C. Le Poncin-Lafitte, V. Lainey, A. F&amp;#xfc;zfa, J.-M. Courty, V. Dehant, P. Wolf </p> <p class="story_para"> <b>Date</b>: 24 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: In this paper, we focus on the possibility to test General Relativity in the Solar System with radioscience measurements. To this aim, we present a new software that simulates Range and Doppler signals directly from the space-time metric. This flexible approach allows one to perform simulations in General Relativity and in alternative metric theories of gravity. In a second step, a least-squares fit of the different initial conditions involved in the situation is performed in order to compare anomalous signals produced by a given alternative theory with the ones obtained in General Relativity. This software provides orders of magnitude and signatures stemming from hypothetical alternative theories of gravity on radioscience signals. As an application, we present some simulations done for the Cassini mission in Post-Einsteinian Gravity and in the context of MOND External Field Effect. We deduce constraints on the Post-Einsteinian parameters but find that the considered arc of the Cassini mission is not useful to constrain the MOND External Field Effect. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.5041">abs</a> <a href="http://www.arxiv.org/pdf/1201.5041">pdf</a></p> http://www.vallis.org/blogspace/2012/01/24#1201.4656 <p class="story_para"> <b>Authors</b>: Miroslav Shaltev </p> <p class="story_para"> <b>Date</b>: 23 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: We derive two different methods to compute the minimal required integration time of a fully coherent follow-up of candidates produced in wide parameter space semi-coherent searches, such as global correlation StackSlide searches using Einstein@Home. We numerically compare these methods in terms of integration duration and computing cost. In a Monte Carlo study we confirm that we can achieve the required detection probability. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.4656">abs</a> <a href="http://www.arxiv.org/pdf/1201.4656">pdf</a></p> http://www.vallis.org/blogspace/2012/01/24#1201.4413 <p class="story_para"> <b>Authors</b>: <!--function toggleAuthorList(whichLayer,toggleThis){ var elem, vis, tempToggle; tempToggle=toggleThis; if( document.getElementById ) // standard elem = document.getElementById( whichLayer ); else if( document.all ) // old msie versions elem = document.all[whichLayer]; else if( document.layers ) // nn4 elem = document.layers[whichLayer]; vis = elem.style; // if the style.display value is blank we try to figure it out here&emsp;if(vis.display==''&amp;&amp;elem.offsetWidth&ne;undefined&amp;&amp;elem.offsetHeight&ne;undefined) vis.display = (elem.offsetWidth&ne;0&amp;&amp;elem.offsetHeight&ne;0)?'inline':'none'; vis.display = (vis.display==''||vis.display=='inline')?'none':'inline'; // toggle link inner text&emsp;status = vis.display; if(status=='none'){ document.getElementById('toggle').innerHTML = tempToggle + ")"; document.getElementById('toggle').title = "Show Entire Author List"; } else if(status=='inline'){ document.getElementById('toggle').innerHTML = "(collapse list)"; document.getElementById('toggle').title = "Collapse Author List"; }}//-->The LIGO Scientific Collaboration: J. Abadie, B. P. Abbott, T. D. Abbott, R. Abbott, M. Abernathy, C. Adams, R. Adhikari, C. Affeldt, P. Ajith, B. Allen, G. S. Allen, E. Amador Ceron, D. Amariutei, R. S. Amin, S. B. Anderson, W. G. Anderson, K. Arai, M. A. Arain, M. C. Araya, S. M. Aston, D. Atkinson, P. Aufmuth, C. Aulbert, B. E. Aylott, S. Babak, P. Baker, S. Ballmer, D. Barker, S. Barnum, B. Barr, P. Barriga, L. Barsotti, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, J. Bauchrowitz, B. Behnke, A. S. Bell, I. Belopolski, M. Benacquista, A. Bertolini, J. Betzwieser, N. Beveridge, P. T. Beyersdorf, I. A. Bilenko, G. Billingsley, J. Birch, R. Biswas, E. Black, J. K. Blackburn, L. Blackburn, D. Blair, B. Bland, O. Bock, T. P. Bodiya, C. Bogan, R. Bondarescu, R. Bork, M. Born, S. Bose, M. Boyle, P. R. Brady, V. B. Braginsky, J. E. Brau, J. Breyer, D. O. Bridges, M. Brinkmann, M. Britzger, A. F. Brooks, D. A. Brown, A. Brummitt, A. Buonanno, J. Burguet-Castell, O. Burmeister, R. L. Byer, L. Cadonati, J. B. Camp, P. Campsie, J. Cannizzo, K. Cannon, J. Cao, C. Capano, S. Caride, S. Caudill, M. Cavaglia, C. Cepeda, T. Chalermsongsak, E. Chalkley, P. Charlton, S. Chelkowski, Y. Chen, N. Christensen, S. S. Y. Chua, S. Chung, C. T. Y. Chung, F. Clara, D. Clark, J. Clark, J. H. Clayton, R. Conte, D. Cook, T. R. C. Corbitt, N. Cornish, C. A. Costa, M. Coughlin, D. M. Coward, D. C. Coyne, J. D. E. Creighton, T. D. Creighton, A. M. Cruise, A. Cumming, L. Cunningham, R. M. Culter, K. Dahl, S. L. Danilishin, R. Dannenberg, K. Danzmann, K. Das, B. Daudert, H. Daveloza, G. Davies, E. J. Daw, T. Dayanga, D. DeBra, J. Degallaix, T. Dent, V. Dergachev, R. DeRosa, R. DeSalvo, S. Dhurandhar, I. Di Palma, M. Diaz, F. Donovan, K. L. Dooley, S. Dorsher, E. S. D. Douglas, R. W. P. Drever, J. C. Driggers, J. -C. Dumas, S. Dwyer, T. Eberle, M. Edgar, M. Edwards, A. Effler, P. Ehrens, R. Engel, T. Etzel, M. Evans, T. Evans, M. Factourovich, S. Fairhurst, Y. Fan, B. F. Farr, D. Fazi, H. Fehrmann, D. Feldbaum, L. S. Finn, M. Flanigan, S. Foley, E. Forsi, N. Fotopoulos, M. Frede, M. Frei, Z. Frei, A. Freise, R. Frey, T. T. Fricke, D. Friedrich, P. Fritschel, V. V. Frolov, P. Fulda, M. Fyffe, J. Garcia, J. A. Garofoli, I. Gholami, S. Ghosh, J. A. Giaime, S. Giampanis, K. D. Giardina, C. Gill, E. Goetz, L. M. Goggin, G. Gonzalez, M. L. Gorodetsky, S. Gossler, C. Graef, A. Grant, S. Gras, C. Gray, R. J. S. Greenhalgh, A. M. Gretarsson, R. Grosso, H. Grote, S. Grunewald, C. Guido, R. Gupta, E. K. Gustafson, R. Gustafson, B. Hage, J. M. Hallam, D. Hammer, G. Hammond, J. Hanks, C. Hanna, J. Hanson, J. Harms, G. M. Harry, I. W. Harry, E. D. Harstad, M. T. Hartman, K. Haughian, K. Hayama, J. Heefner, M. A. Hendry, I. S. Heng, A. W. Heptonstall, V. Herrera, M. Hewitson, S. Hild, D. Hoak, K. A. Hodge, K. Holt, T. Hong, S. Hooper, D. J. Hosken, J. Hough, E. J. Howell, B. Hughey, S. Husa, S. H. Huttner, D. R. Ingram, R. Inta, T. Isogai, A. Ivanov, W. W. Johnson, D. I. Jones, G. Jones, R. Jones, L. Ju, P. Kalmus, V. Kalogera, S. Kandhasamy, J. B. Kanner, E. Katsavounidis, W. Katzman, K. Kawabe, S. Kawamura, F. Kawazoe, W. Kells, M. Kelner, D. G. Keppel, A. Khalaidovski, F. Y. Khalili, E. A. Khazanov, N. Kim, H. Kim, P. J. King, D. L. Kinzel, J. S. Kissel, S. Klimenko, V. Kondrashov, R. Kopparapu, S. Koranda, W. Z. Korth, D. Kozak, V. Kringel, S. Krishnamurthy, B. Krishnan, G. Kuehn, R. Kumar, P. Kwee, M. Landry, B. Lantz, N. Lastzka, A. Lazzarini, P. Leaci, J. Leong, I. Leonor, J. Li, P. E. Lindquist, N. A. Lockerbie, D. Lodhia, M. Lormand, P. Lu, J. Luan, M. Lubinski, H. Luck, A. P. Lundgren, E. Macdonald, B. Machenschalk, M. MacInnis, M. Mageswaran, K. Mailand, I. Mandel, V. Mandic, A. Marandi, S. Marka, Z. Marka, E. Maros, I. W. Martin, R. M. Martin, J. N. Marx, K. Mason, F. Matichard, L. Matone, R. A. Matzner, N. Mavalvala, R. McCarthy, D. E. McClelland, S. C. McGuire, G. McIntyre, J. McIver, D. J. A. McKechan, G. Meadors, M. Mehmet, T. Meier, A. Melatos, A. C. Melissinos, G. Mendell, R. A. Mercer, S. Meshkov, C. Messenger, M. S. Meyer, H. Miao, J. Miller, Y. Mino, V. P. Mitrofanov, G. Mitselmakher, R. Mittleman, O. Miyakawa, B. Moe, P. Moesta, S. D. Mohanty, D. Moraru, G. Moreno, K. Mossavi, C. M. Mow-Lowry, G. Mueller, S. Mukherjee, A. Mullavey, H. Muller-Ebhardt, J. Munch, D. Murphy, P. G. Murray, T. Nash, R. Nawrodt, J. Nelson, G. Newton, A. Nishizawa, D. Nolting, L. Nuttall, B. O&amp;#x27;Reilly, R. O&amp;#x27;Shaughnessy, E. Ochsner, J. O&amp;#x27;Dell, G. H. Ogin, R. G. Oldenburg, C. Osthelder, C. D. Ott, D. J. Ottaway, R. S. Ottens, H. Overmier, B. J. Owen, A. Page, Y. Pan, C. Pankow, M. A. Papa, P. Patel, M. Pedraza, L. Pekowsky, S. Penn, C. Peralta, A. Perreca, M. Phelps, M. Pickenpack, I. M. Pinto, M. Pitkin, H. J. Pletsch, M. V. Plissi, J. Podkaminer, J. Pold, F. Postiglione, V. Predoi, L. R. Price, M. Prijatelj, M. Principe, S. Privitera, R. Prix, L. Prokhorov, O. Puncken, V. Quetschke, F. J. Raab, H. Radkins, P. Raffai, M. Rakhmanov, C. R. Ramet, B. Rankins, S. R. P. Mohapatra, V. Raymond, K. Redwine, C. M. Reed, T. Reed, S. Reid, D. H. Reitze, R. Riesen, K. Riles, P. Roberts, N. A. Robertson, C. Robinson, E. L. Robinson, S. Roddy, J. Rollins, J. D. Romano, J. H. Romie, C. Rover, S. Rowan, A. Rudiger, K. Ryan, S. Sakata, M. Sakosky, F. Salemi, M. Salit, L. Sammut, L. Sancho de la Jordana, V. Sandberg, V. Sannibale, L. Santamar&amp;#xcc;a, I. Santiago-Prieto, G. Santostasi, S. Saraf, B. S. Sathyaprakash, S. Sato, P. R. Saulson, R. Savage, R. Schilling, S. Schlamminger, R. Schnabel, R. M. S. Schofield, B. Schulz, B. F. Schutz, P. Schwinberg, J. Scott, S. M. Scott, A. C. Searle, F. Seifert, D. Sellers, A. S. Sengupta, A. Sergeev, D. A. Shaddock, M. Shaltev, B. Shapiro, P. Shawhan, T. Shihan Weerathunga, D. H. Shoemaker, A. Sibley, X. Siemens, D. Sigg, A. Singer, L. Singer, A. M. Sintes, G. Skelton, B. J. J. Slagmolen, J. Slutsky, R. Smith, J. R. Smith, M. R. Smith, N. D. Smith, K. Somiya, B. Sorazu, J. Soto, F. C. Speirits, A. J. Stein, J. Steinlechner, S. Steinlechner, S. Steplewski, M. Stefszky, A. Stochino, R. Stone, K. A. Strain, S. Strigin, A. S. Stroeer, A. L. Stuver, T. Z. Summerscales, M. Sung, S. Susmithan, P. J. Sutton, G. P. Szokoly, D. Talukder, D. B. Tanner, S. P. Tarabrin, J. R. Taylor, R. Taylor, P. Thomas, K. A. Thorne, K. S. Thorne, E. Thrane, A. Thuring, K. V. Tokmakov, C. Torres, C. I. Torrie, G. Traylor, M. Trias, K. Tseng, D. Ugolini, K. Urbanek, H. Vahlbruch, B. Vaishnav, M. Vallisneri, C. Van Den Broeck, M. V. van der Sluys, A. A. van Veggel, S. Vass, R. Vaulin, A. Vecchio, J. Veitch, P. J. Veitch, C. Veltkamp, A. E. Villar, C. Vorvick, S. P. Vyachanin, S. J. Waldman, L. Wallace, A. Wanner, R. L. Ward, P. Wei, M. Weinert, A. J. Weinstein, R. Weiss, L. Wen, S. Wen, P. Wessels, M. West, T. Westphal, K. Wette, J. T. Whelan, S. E. Whitcomb, D. White, B. F. Whiting, C. Wilkinson, P. A. Willems, H. R. Williams, L. Williams, B. Willke, L. Winkelmann, W. Winkler, C. C. Wipf, A. G. Wiseman, G. Woan, R. Wooley, J. Worden, J. Yablon, I. Yakushin, K. Yamamoto, H. Yamamoto, H. Yang, D. Yeaton-Massey, S. Yoshida, P. Yu, M. Zanolin, L. Zhang, Z. Zhang, C. Zhao, N. Zotov, M. E. Zucker, J. Zweizig, M. A. Bizouard, A. Dietz, G. M. Guidi, M. Was </p> <p class="story_para"> <b>Date</b>: 21 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: We present the results of a LIGO search for gravitational waves (GWs) associated with GRB 051103, a short-duration hard-spectrum gamma-ray burst (GRB) whose electromagnetically determined sky position is coincident with the spiral galaxy M81, which is 3.6 Mpc from Earth. Possible progenitors for short-hard GRBs include compact object mergers and soft gamma repeater (SGR) giant flares. A merger progenitor would produce a characteristic GW signal that should be detectable at the distance of M81, while GW emission from an SGR is not expected to be detectable at that distance. We found no evidence of a GW signal associated with GRB 051103. Assuming weakly beamed gamma-ray emission with a jet semi-angle of 30 deg we exclude a binary neutron star merger in M81 as the progenitor with a confidence of 98%. Neutron star-black hole mergers are excluded with &gt; 99% confidence. If the event occurred in M81 our findings support the the hypothesis that GRB 051103 was due to an SGR giant flare, making it the most distant extragalactic magnetar observed to date. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.4413">abs</a> <a href="http://www.arxiv.org/pdf/1201.4413">pdf</a></p> http://www.vallis.org/blogspace/2012/01/24#1201.4389 <p class="story_para"> <b>Authors</b>: Roland Haas, Roman V. Shcherbakov, Tanja Bode, Pablo Laguna </p> <p class="story_para"> <b>Date</b>: 20 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: We present numerical relativity results of tidal disruptions of white dwarfs from ultra-close encounters with a spinning, intermediate mass black hole. These encounters require a full general relativistic treatment of gravity. We show that the disruption process and prompt accretion of the debris strongly depend on the magnitude and orientation of the black hole spin. However, the late-time accretion onto the black hole follows the same decay, $\dot{M}$ ~ t&circ;{-5/3}, estimated from Newtonian gravity disruption studies. We compute the spectrum of the disk formed from the fallback material using a slim disk model. The disk spectrum peaks in the soft X-rays and sustains Eddington luminosity for 1-3 yrs after the disruption. For arbitrary black hole spin orientations, the disrupted material is scattered away from the orbital plane by relativistic frame dragging, which often leads to obscuration of the inner fallback disk by the outflowing debris. The disruption events also yield bursts of gravitational radiation with characteristic frequencies of ~3.2 Hz and strain amplitudes of ~10&circ;{-18} for galactic intermediate mass black holes. The optimistic rate of considered ultra-close disruptions is consistent with no sources found in ROSAT all-sky survey. The future missions like Wide-Field X-ray Telescope (WFXT) could observe dozens of events. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.4389">abs</a> <a href="http://www.arxiv.org/pdf/1201.4389">pdf</a></p> http://www.vallis.org/blogspace/2012/01/22#1201.4321 <p class="story_para"> <b>Authors</b>: Reinhard Prix, Miroslav Shaltev </p> <p class="story_para"> <b>Date</b>: 20 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: Coherent wide parameter-space searches for continuous gravitational waves are typically limited in sensitivity by their prohibitive computing cost. Therefore semi-coherent methods (such as StackSlide) can often achieve a better sensitivity. We develop an analytical method for finding optimal StackSlide parameters at fixed computing cost under ideal conditions of gapless data with Gaussian stationary noise. This solution separates two regimes: an unbounded regime, where it is always optimal to use all the data, and a bounded regime with a finite optimal observation time. Our analysis of the sensitivity scaling reveals that both the fine- and coarse-grid mismatches contribute equally to the average StackSlide mismatch, an effect that had been overlooked in previous studies. We discuss various practical examples for the application of this optimization framework, illustrating the potential gains in sensitivity compared to previous searches. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.4321">abs</a> <a href="http://www.arxiv.org/pdf/1201.4321">pdf</a></p> http://www.vallis.org/blogspace/2012/01/19#1201.3573 <p class="story_para"> <b>Authors</b>: Matthew Pitkin </p> <p class="story_para"> <b>Date</b>: 17 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: Pulsar timing arrays (PTAs) are being used to search for very low frequency gravitational waves. Gravitational waves imprint their signal in the observed pulse time of arrivals from when they passed the pulsar and as they pass the Earth. In searches for gravitational wave bursts with PTAs (e.g. Finn &amp; Lommen, 2010) the pulsar term is generally ignored as only the Earth term will be coherent between all pulsars in the array, whereas signals in the pulsar terms may be separated by delays on the order of the pulsar distance. However, we show that for a set of pulsars (made up from those in the International Pulsar Timing Array) there are areas of the sky where the alignment between pairs, or more, of pulsars and a source are serendipitously placed to give pulsar terms that are separated by feasible (10-20 year) observing times. The data from these pulsars can therefore be coherently combined, with the appropriate sky position delay, to search for gravitational wave bursts. This increases the time-span over which bursts could be observed to be many times that covered by the PTA observation span. Assuming perfectly known pulsar distances we show that sources over approximately 70 per cent of the sky produce pulsar term signals separated by less than 10 years within at least one pair of pulsars. We study the effect of pulsar distance uncertainties on the sky coverage. We also assess a simplified method for detecting burst sources from these sky positions with a toy two-pulsar array. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.3573">abs</a> <a href="http://www.arxiv.org/pdf/1201.3573">pdf</a></p> http://www.vallis.org/blogspace/2012/01/19#1201.3563 <p class="story_para"> <b>Authors</b>: Tania Regimbau, Thomas Dent, Walter Del Pozzo, Stefanos Giampanis, Tjonnie G. F. Li, Craig Robinson, Chris Van Den Broeck, Duncan Meacher, Carl Rodriguez, Bangalore S. Sathyaprakash, Katarzyna W&amp;#xf3;jcik </p> <p class="story_para"> <b>Date</b>: 17 Jan 2012 </p> <p class="story_para"> <b>Abstract</b>: Einstein Telescope (ET) is conceived to be a third generation gravitational-wave observatory. Its amplitude sensitivity would be a factor ten better than advanced LIGO and Virgo and it could also extend the low-frequency sensitivity down to 1--3\,Hz, compared to the 10--20\,Hz of advanced detectors. Such an observatory will have the potential to observe a variety of different GW sources, including compact binary systems at cosmological distances. ET's expected reach for binary neutron star (BNS) coalescences is out to redshift $z\simeq 2$ and the rate of detectable BNS coalescences could be as high as one every few tens or hundreds of seconds, each lasting up to several days. %in the sensitive frequency band of ET. With such a signal-rich environment, a key question in data analysis is whether overlapping signals can be discriminated. In this paper we simulate the GW signals from a cosmological population of BNS and ask the following questions: Does this population create a confusion background that limits ET's ability to detect foreground sources? How efficient are current algorithms in discriminating overlapping BNS signals? Is it possible to discern the presence of a population of signals in the data by cross-correlating data from different detectors in the ET observatory? We find that algorithms currently used to analyze LIGO and Virgo data are already powerful enough to detect the sources expected in ET, but new algorithms are required to fully exploit ET data. </p> <p class="story_para"> <a href="http://www.arxiv.org/abs/1201.3563">abs</a> <a href="http://www.arxiv.org/pdf/1201.3563">pdf</a></p>