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University of Texas Rio Grande Valley

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Articles 721 - 750 of 832

Full-Text Articles in Astrophysics and Astronomy

Beating The Spin-Down Limit On Gravitational Wave Emission From The Crab Pulsar, B. P. Abbott, R. Abbott, R. Adhikari, Mario C. Diaz, Roberto Grosso, Kazuhiro Hayama, Soumya Mohanty, Soma Mukherjee, Joseph D. Romano, Robert Stone Jan 2008

Beating The Spin-Down Limit On Gravitational Wave Emission From The Crab Pulsar, B. P. Abbott, R. Abbott, R. Adhikari, Mario C. Diaz, Roberto Grosso, Kazuhiro Hayama, Soumya Mohanty, Soma Mukherjee, Joseph D. Romano, Robert Stone

Physics & Astronomy Faculty Publications

We present direct upper limits on gravitational wave emission from the Crab pulsar using data from the first 9 months of the fifth science run of the Laser Interferometer Gravitational-wave Observatory (LIGO). These limits are based on two searches. In the first we assume that the gravitational wave emission follows the observed radio timing, giving an upper limit on gravitational wave emission that beats indirect limits inferred from the spin-down and braking index of the pulsar and the energetics of the nebula. In the second we allow for a small mismatch between the gravitational and radio signal frequencies and interpret …

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Search Of S3 Ligo Data For Gravitational Wave Signals From Spinning Black Hole And Neutron Star Binary Inspirals, B. P. Abbott, R. Grosso, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Jan 2008

Search Of S3 Ligo Data For Gravitational Wave Signals From Spinning Black Hole And Neutron Star Binary Inspirals, B. P. Abbott, R. Grosso, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We report on the methods and results of the first dedicated search for gravitational waves emitted during the inspiral of compact binaries with spinning component bodies. We analyze 788 hours of data collected during the third science run (S3) of the LIGO detectors. We searched for binary systems using a detection template family specially designed to capture the effects of the spin-induced precession of the orbital plane. We present details of the techniques developed to enable this search for spin-modulated gravitational waves, highlighting the differences between this and other recent searches for binaries with nonspinning components. The template bank we …

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Search For Gravitational Waves Associated With 39 Gamma-Ray Bursts Using Data From The Second, Third, And Fourth Ligo Runs, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Wm. R. Johnston, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Jan 2008

Search For Gravitational Waves Associated With 39 Gamma-Ray Bursts Using Data From The Second, Third, And Fourth Ligo Runs, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Wm. R. Johnston, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We present the results of a search for short-duration gravitational-wave bursts associated with 39 gamma-ray bursts (GRBs) detected by gamma-ray satellite experiments during LIGO’s S2, S3, and S4 science runs. The search involves calculating the crosscorrelation between two interferometer data streams surrounding the GRB trigger time. We search for associated gravitational radiation from single GRBs, and also apply statistical tests to search for a gravitational-wave signature associated with the whole sample. For the sample examined, we find no evidence for the association of gravitational radiation with GRBs, either on a single-GRB basis or on a statistical basis. Simulating gravitational-wave bursts …

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Denaturation Transition Of Stretched Dna, Andreas Hanke, Martha G. Ochoa, Ralf Metzler Jan 2008

Denaturation Transition Of Stretched Dna, Andreas Hanke, Martha G. Ochoa, Ralf Metzler

Physics & Astronomy Faculty Publications

We generalize the Poland-Scheraga model to consider DNA denaturation in the presence of an external stretching force. We demonstrate the existence of a force-induced DNA denaturation transition and obtain the temperature-force phase diagram. The transition is determined by the loop exponent c, for which we find the new value c=4ν−1/2 such that the transition is second order with c=1.85DNA, corresponding to a lower melting temperature T(F), in agreement with single-molecule DNA stretching experiments.

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Zinc Cysteine Active Sites Of Metalloproteins: A Density Functional Theory And X-Ray Absorption Fine Structure Study, Nicholas Dimakis, Mohammed Junaid Farooqi, Emily Sofia Garza, Grant Bunker Dec 2007

Zinc Cysteine Active Sites Of Metalloproteins: A Density Functional Theory And X-Ray Absorption Fine Structure Study, Nicholas Dimakis, Mohammed Junaid Farooqi, Emily Sofia Garza, Grant Bunker

Physics & Astronomy Faculty Publications

Density functional theory (DFT) and x-ray absorption fine structure (XAFS) spectroscopy are complementary tools for the biophysical study of active sites in metalloproteins. DFT is used to compute XAFS multiple scattering Debye Waller factors, which are then employed in genetic algorithm-based fitting process to obtain a global fit to the XAFS in the space of fitting parameters. Zn-Cys sites, which serve important functions as transcriptional switches in Zn finger proteins and matrix metalloproteinases, previously have proven intractable by this method; here these limitations are removed. In this work we evaluate optimal DFT nonlocal functionals and basis sets for determining optimal …

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Upper Limit Map Of A Background Of Gravitational Waves, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Oct 2007

Upper Limit Map Of A Background Of Gravitational Waves, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We searched for an anisotropic background of gravitational waves using data from the LIGO S4 science run and a method that is optimized for point sources. This is appropriate if, for example, the gravitational wave background is dominated by a small number of distinct astrophysical sources. No signal was seen. Upper limit maps were produced assuming two different power laws for the source strain power spectrum. For an f−3 power law and using the 50 Hz to 1.8 kHz band the upper limits on the source strain power spectrum vary between 1.2×10−48  Hz−1 (100  Hz/f)3 and 1.2×10−47  Hz−1 (100  Hz/f)3, …

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Fundamental Emission Via Wave Advection From A Collapsing Wave Packet In Electromagnetic Strong Plasma Turbulence, Fredrick A. Jenet, A. Melatos, P. A. Robinson Oct 2007

Fundamental Emission Via Wave Advection From A Collapsing Wave Packet In Electromagnetic Strong Plasma Turbulence, Fredrick A. Jenet, A. Melatos, P. A. Robinson

Physics & Astronomy Faculty Publications

Zakharov simulations of nonlinear wave collapse in continuously driven two-dimensional, electromagnetic strong plasma turbulence with electron thermal speeds v⩾0.01c show that for v≲0.1c, dipole radiation occurs near the plasma frequency, mainly near arrest, but for v≳0.1c, a new mechanism applies in which energy oscillates between trapped Langmuir and transverse modes until collapse is arrested, after which trapped transverse waves are advected into incoherent interpacket turbulence by an expanding annular density well, where they detrap. The multipole structure, Poynting flux, source current, and radiation angular momentum are computed.

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Searches For Periodic Gravitational Waves From Unknown Isolated Sources And Scorpius X-1: Results From The Second Ligo Science Run, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Wm. R. Johnston, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Oct 2007

Searches For Periodic Gravitational Waves From Unknown Isolated Sources And Scorpius X-1: Results From The Second Ligo Science Run, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Wm. R. Johnston, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We carry out two searches for periodic gravitational waves using the most sensitive few hours of data from the second LIGO science run. Both searches exploit fully coherent matched filtering and cover wide areas of parameter space, an innovation over previous analyses which requires considerable algorithm development and computational power. The first search is targeted at isolated, previously unknown neutron stars, covers the entire sky in the frequency band 160–728.8 Hz, and assumes a frequency derivative of less than 4×10−10  Hz/s. The second search targets the accreting neutron star in the low-mass x-ray binary Scorpius X-1 and covers the frequency …

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Stellar Population Models And Individual Element Abundances. I. Sensitivity Of Stellar Evolution Models, Aaron Dotter, Brian Chaboyer, Jason W. Ferguson, Hyun Chul Lee, Guy Worthey, Darko Jevremović, E. Baron Sep 2007

Stellar Population Models And Individual Element Abundances. I. Sensitivity Of Stellar Evolution Models, Aaron Dotter, Brian Chaboyer, Jason W. Ferguson, Hyun Chul Lee, Guy Worthey, Darko Jevremović, E. Baron

Physics & Astronomy Faculty Publications

Integrated light from distant galaxies is often compared to stellar population models via the equivalent widths of spectral features-spectral indices-whose strengths rely on the abundances of one or more elements. Such comparisons hinge not only on the overall metal abundance, but also on relative abundances. Studies have examined the influence of individual elements on synthetic spectra but little has been done to address similar issues in the stellar evolution models that underlie most stellar population models. Stellar evolution models will primarily be influenced by changes in opacities. In order to explore this issue in detail, 12 sets of stellar evolution …

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Search For Gravitational Wave Radiation Associated With The Pulsating Tail Of The Sgr 1806−20 Hyperflare Of 27 December 2004 Using Ligo, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Sep 2007

Search For Gravitational Wave Radiation Associated With The Pulsating Tail Of The Sgr 1806−20 Hyperflare Of 27 December 2004 Using Ligo, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We have searched for gravitational waves (GWs) associated with the SGR 1806−20 hyperflare of 27 December 2004. This event, originating from a Galactic neutron star, displayed exceptional energetics. Recent investigations of the x-ray light curve’s pulsating tail revealed the presence of quasiperiodic oscillations (QPOs) in the 30–2000 Hz frequency range, most of which coincides with the bandwidth of the LIGO detectors. These QPOs, with well-characterized frequencies, can plausibly be attributed to seismic modes of the neutron star which could emit GWs. Our search targeted potential quasimonochromatic GWs lasting for tens of seconds and emitted at the QPO frequencies. We have …

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Upper Limits On Gravitational Wave Emission From 78 Radio Pulsars, B. P. Abbott, R. Abbott, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Aug 2007

Upper Limits On Gravitational Wave Emission From 78 Radio Pulsars, B. P. Abbott, R. Abbott, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We present upper limits on the gravitational wave emission from 78 radio pulsars based on data from the third and fourth science runs of the LIGO and GEO 600 gravitational wave detectors. The data from both runs have been combined coherently to maximize sensitivity. For the first time, pulsars within binary (or multiple) systems have been included in the search by taking into account the signal modulation due to their orbits. Our upper limits are therefore the first measured for 56 of these pulsars. For the remaining 22, our results improve on previous upper limits by up to a factor …

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On The Age And Metallicity Estimation Of Spiral Galaxies Using Optical And Near-Infrared Photometry, Hyun Chul Lee, Guy Worthey, Scott C. Trager, S. M. Faber Jul 2007

On The Age And Metallicity Estimation Of Spiral Galaxies Using Optical And Near-Infrared Photometry, Hyun Chul Lee, Guy Worthey, Scott C. Trager, S. M. Faber

Physics & Astronomy Faculty Publications

In integrated light, some color-color diagrams that use optical and near-infrared photometry show surprisingly orthogonal grids as age and metallicity are varied, and they are coming into common usage for estimating the average age and metallicity of spiral galaxies. In this paper we reconstruct these composite grids using simple stellar population models from several different groups convolved with some plausible functional forms of star formation histories at fixed metallicity. We find that the youngest populations present (t < 2 Gyr) dominate the light, and because of their presence the age-metallicity degeneracy can be partially broken with broadband colors, unlike older populations. The scatter among simple stellar population models by different authors is, however, large at ages t < 2 Gyr. The dominant uncertainties in stellar population models arise from convective core overshoot assumptions and the treatment of the thermally pulsing asymptotic giant branch phase and helium abundance may play a significant role at higher metallicities. Real spiral galaxies are unlikely to have smooth, exponential star formation histories, and burstiness will cause a partial reversion to the single-burst case, which has even larger model-to-model scatter. Finally, it is emphasized that the current composite stellar population models need some implementation of chemical enrichment histories for the proper analysis of the observational data. © 2007. The American Astronomical Society. All rights reserved.

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Dispersion Measure Variations And Their Effect On Precision Pulsar Timing, X. P. You, G. Hobbs, W. A. Coles, R. N. Manchester, R. Edwards, M. Bailes, J. Sarkissian, J. P.W. Verbiest, Fredrick Jenet Jun 2007

Dispersion Measure Variations And Their Effect On Precision Pulsar Timing, X. P. You, G. Hobbs, W. A. Coles, R. N. Manchester, R. Edwards, M. Bailes, J. Sarkissian, J. P.W. Verbiest, Fredrick Jenet

Physics & Astronomy Faculty Publications

We present an analysis of the variations seen in the dispersion measures (DMs) of 20-ms pulsars observed as part of the Parkes Pulsar Timing Array project. We carry out a statistically rigorous structure function analysis for each pulsar and show that the variations seen for most pulsars are consistent with those expected for an interstellar medium characterized by a Kolmogorov turbulence spectrum. The structure functions for PSRs J1045-4509 and J1909-3744 provide the first clear evidence for a large inner scale, possibly due to ion-neutral damping. We also show the effect of the solar wind on the DMs and show that …

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Searching For A Stochastic Background Of Gravitational Waves With The Laser Interferometer Gravitational-Wave Observatory, B. Abbott, R. Abbott, R. Adhikari, J. Agresti, Mario C. Diaz, Roberto Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Apr 2007

Searching For A Stochastic Background Of Gravitational Waves With The Laser Interferometer Gravitational-Wave Observatory, B. Abbott, R. Abbott, R. Adhikari, J. Agresti, Mario C. Diaz, Roberto Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

The Laser Interferometer Gravitational-Wave Observatory (LIGO) has performed the fourth science run, S4, with significantly improved interferometer sensitivities with respect to previous runs. Using data acquired during this science run, we place a limit on the amplitude of a stochastic background of gravitational waves. For a frequency independent spectrum, the new Bayesian 90% upper limit is ΩGW × [H0/(12 km s-1 Mpc-1)]2 < 6.5 × 10-5. This is currently the most sensitive result in the frequency range 51-150 Hz, with a factor of 13 improvement over the previous LIGO result. We discuss the complementarity of the new result with other constraints on a stochastic background of gravitational waves, and we investigate implications of the new result for different models of this background. © 2007. The American Astronumical Society. All rights reserved.

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Large Merger Recoils And Spin Flips From Generic Black Hole Binaries, Manuela Campanelli, Carlos O. Lousto, Y. Zlochower, David Merritt Mar 2007

Large Merger Recoils And Spin Flips From Generic Black Hole Binaries, Manuela Campanelli, Carlos O. Lousto, Y. Zlochower, David Merritt

Physics & Astronomy Faculty Publications

We report the first results from the evolution of generic black hole binaries, i.e., binaries containing unequal-mass black holes with misaligned spins. Our configuration, which has a mass ratio of 2 : 1, consists of an initially nonspinning hole orbiting a larger, rapidly spinning hole (specific spin a/m = 0.885), with the spin direction oriented -45° with respect to the orbital plane. We track the inspiral and merger for ~2 orbits and find that the remnant receives a substantial kick of 454 km s-1, more than twice as large as the maximum kick from nonspinning binaries. The remnant …

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Searches For Periodic Gravitational Waves From Unknown Isolated Sources And Scorpius X-1: Results From The Second Ligo Science Run, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Wm. R. Johnston, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Jan 2007

Searches For Periodic Gravitational Waves From Unknown Isolated Sources And Scorpius X-1: Results From The Second Ligo Science Run, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Wm. R. Johnston, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We carry out two searches for periodic gravitational waves using the most sensitive few hours of data from the second LIGO science run. Both searches exploit fully coherent matched filtering and cover wide areas of parameter space, an innovation over previous analyses which requires considerable algorithm development and computational power. The first search is targeted at isolated, previously unknown neutron stars, covers the entire sky in the frequency band 160–728.8 Hz, and assumes a frequency derivative of less than 4×10−10  Hz/s. The second search targets the accreting neutron star in the low-mass x-ray binary Scorpius X-1 and covers the frequency …

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Spin Flips And Precession In Black-Hole-Binary Mergers, Manuela Campanelli, Carlos O. Lousto, Z. Zlochower, Badri Krishnan, David Merritt Jan 2007

Spin Flips And Precession In Black-Hole-Binary Mergers, Manuela Campanelli, Carlos O. Lousto, Z. Zlochower, Badri Krishnan, David Merritt

Physics & Astronomy Faculty Publications

We use the “moving puncture” approach to perform fully nonlinear evolutions of spinning quasicircular black-hole binaries with individual spins unaligned with the orbital angular momentum. We evolve configurations with the individual spins (parallel and equal in magnitude) pointing in the orbital plane and 45° above the orbital plane. We introduce a technique to measure the spin direction and track the precession of the spin during the merger, as well as measure the spin flip in the remnant horizon. The former configuration completes 1.75 orbits before merging, with the spin precessing by 98° and the final remnant horizon spin flipped by …

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First Cross-Correlation Analysis Of Interferometric And Resonant-Bar Gravitational-Wave Data For Stochastic Backgrounds, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Jan 2007

First Cross-Correlation Analysis Of Interferometric And Resonant-Bar Gravitational-Wave Data For Stochastic Backgrounds, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

Data from the LIGO Livingston interferometer and the ALLEGRO resonant-bar detector, taken during LIGO’s fourth science run, were examined for cross correlations indicative of a stochastic gravitational-wave background in the frequency range 850–950 Hz, with most of the sensitivity arising between 905 and 925 Hz. ALLEGRO was operated in three different orientations during the experiment to modulate the relative sign of gravitational-wave and environmental correlations. No statistically significant correlations were seen in any of the orientations, and the results were used to set a Bayesian 90% confidence level upper limit of Ωgw(f)≤1.02, which corresponds to a gravitational-wave strain at 915 …

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Single Dna Conformations And Biological Function, Ralf Metzler, Tobias Ambjoernsson, Andreas Hanke, Yongli Zhang, Stephen Levene Jan 2007

Single Dna Conformations And Biological Function, Ralf Metzler, Tobias Ambjoernsson, Andreas Hanke, Yongli Zhang, Stephen Levene

Physics & Astronomy Faculty Publications

From a nanoscience perspective, cellular processes and their reduced in vitro imitations provide extraordinary examples for highly robust few or single molecule reaction pathways. A prime example are biochemical reactions involving DNA molecules, and the coupling of these reactions to the physical conformations of DNA. In this review, we summarise recent results on the following phenomena: We investigate the biophysical properties of DNA-looping and the equilibrium configurations of DNA-knots, whose relevance to biological processes are increasingly appreciated. We discuss how random DNA-looping may be related to the efficiency of the target search process of proteins for their specific binding site …

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Electromagnetic Strong Plasma Turbulence, A. Melatos, F. A. Jenet, P. A. Robinson Jan 2007

Electromagnetic Strong Plasma Turbulence, A. Melatos, F. A. Jenet, P. A. Robinson

Physics & Astronomy Faculty Publications

The first large-scale simulations of continuously driven, two-dimensional electromagnetic strong plasma turbulence are performed, for electron thermal speeds 0.01c⩽v⩽0.57c, by integrating the Zakharov equations for coupled Langmuir and transverse (T) waves near the plasma frequency. Turbulence scalings and wave number spectra are calculated, a transition is found from a mix of trapped and free T eigenstates for v⩾0.1c to just free eigenstates for v⩽0.1c, and wave energy densities are observed to undergo slow quasiperiodic oscillations.

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Upper Bounds On The Low-Frequency Stochastic Gravitational Wave Background From Pulsar Timing Observations: Current Limits And Future Prospects, Fredrick Jenet, G. B. Hobbs, W. Van Straten, R. N. Manchester, M. Bailes, J. P.W. Verbiest, R. T. Edwards, A. W. Hotan, J. M. Sarkissian, S. M. Ord Dec 2006

Upper Bounds On The Low-Frequency Stochastic Gravitational Wave Background From Pulsar Timing Observations: Current Limits And Future Prospects, Fredrick Jenet, G. B. Hobbs, W. Van Straten, R. N. Manchester, M. Bailes, J. P.W. Verbiest, R. T. Edwards, A. W. Hotan, J. M. Sarkissian, S. M. Ord

Physics & Astronomy Faculty Publications

Using a statistically rigorous analysis method, we place limits on the existence of an isotropic stochastic gravitational wave background using pulsar timing observations. We consider backgrounds whose characteristic strain spectra may be described as a power-law dependence with frequency. Such backgrounds include an astrophysical background produced by coalescing supermassive black-hole binary systems and cosmological backgrounds due to relic gravitational waves and cosmic strings. Using the best available data, we obtain an upper limit on the energy density per unit logarithmic frequency interval of ΩgSMBH[1/(8 yr)}h2 ≤ 1.9 × 10-8 for an astrophysical background that is 5 times more stringent than …

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The P14 Fusion-Associated Small Transmembrane (Fast) Protein Effects Membrane Fusion From A Subset Of Membrane Microdomains, Jennifer A. Corcoran, Jayme Salsman, Roberto De Antueno, Ahmed Touhami, Manfred H. Jericho, Eileen K. Clancy, Roy Duncan Oct 2006

The P14 Fusion-Associated Small Transmembrane (Fast) Protein Effects Membrane Fusion From A Subset Of Membrane Microdomains, Jennifer A. Corcoran, Jayme Salsman, Roberto De Antueno, Ahmed Touhami, Manfred H. Jericho, Eileen K. Clancy, Roy Duncan

Physics & Astronomy Faculty Publications

The reovirus fusion-associated small transmembrane (FAST) proteins are a unique family of viral membrane fusion proteins. These nonstructural viral proteins induce efficient cell-cell rather than virus-cell membrane fusion. We analyzed the lipid environment in which the reptilian reovirus p14 FAST protein resides to determine the influence of the cell membrane on the fusion activity of the FAST proteins. Topographical mapping of the surface of fusogenic p14-containing liposomes by atomic force microscopy under aqueous conditions revealed that p14 resides almost exclusively in thickened membrane microdomains. In transfected cells, p14 was found in both Lubrol WX-and Triton X-100-resistant membrane complexes. Cholesterol depletion …

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Spinning-Black-Hole Binaries: The Orbital Hang-Up, Manuela Campanelli, Carlos O. Lousto, Y. Zlochower Aug 2006

Spinning-Black-Hole Binaries: The Orbital Hang-Up, Manuela Campanelli, Carlos O. Lousto, Y. Zlochower

Physics & Astronomy Faculty Publications

We present the first fully-nonlinear numerical study of the dynamics of highly-spinning-black-hole binaries. We evolve binaries from quasicircular orbits (as inferred from post-Newtonian theory), and find that the last stages of the orbital motion of black-hole binaries are profoundly affected by their individual spins. In order to cleanly display its effects, we consider two equal-mass holes with individual spin parameters S/m2=0.757, both aligned and antialigned with the orbital angular momentum (and compare with the spinless case), and with an initial orbital period of 125M. We find that the aligned case completes three orbits and merges significantly after the antialigned case, …

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Consequences Of Disk Scale Height On Lisa Confusion Noise From Close White Dwarf Binaries, M. Benacquista, K. Holley-Bockelmann Jul 2006

Consequences Of Disk Scale Height On Lisa Confusion Noise From Close White Dwarf Binaries, M. Benacquista, K. Holley-Bockelmann

Physics & Astronomy Faculty Publications

Gravitational radiation from the Galactic population of close white dwarf binaries (CWDBs) is expected to produce a confusion-limited signal at the lower end of the sensitivity band of the Laser Interferometer Space Antenna (LISA). The canonical scale height of the disk population has been taken to be 90 pc for most studies of the nature of this confusion-limited signal. This estimate is probably too low, and the consequences of a more realistic scale height are investigated with a model of the LISA signal due to populations of CWDBs with different scale heights. If the local space density of CWDBs is …

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Measurement Of Orbital Decay In The Double Neutron Star Binary Psr B2127+11c, B. A. Jacoby, P. B. Cameron, F. A. Jenet, S. B. Anderson, R. N. Murty, S. R. Kulkarni Jun 2006

Measurement Of Orbital Decay In The Double Neutron Star Binary Psr B2127+11c, B. A. Jacoby, P. B. Cameron, F. A. Jenet, S. B. Anderson, R. N. Murty, S. R. Kulkarni

Physics & Astronomy Faculty Publications

We report the direct measurement of orbital period decay in the double neutron star pulsar system PSR B2127 + 11C in the globular cluster M15 at the rate of (-3.95 ± 0.13) × 10-12, consistent with the prediction of general relativity at the ∼3% level. We find the pulsar mass to be mp = 1.358 ± 0.010 M⊙ and the companion mc = 1.354 ± 0.010 M⊙. We also report long-term pulse timing results for the pulsars PSR B2127+11A and PSR B2127+11B, including confirmation of the cluster proper motion.

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Joint Ligo And Tama300 Search For Gravitational Waves From Inspiralling Neutron Star Binaries, B. P. Abbott, R. Abbott, W. G. Anderson, Mario C. Diaz, Wm. R. Johnston, Soma Mukherjee, Cristina V. Torres May 2006

Joint Ligo And Tama300 Search For Gravitational Waves From Inspiralling Neutron Star Binaries, B. P. Abbott, R. Abbott, W. G. Anderson, Mario C. Diaz, Wm. R. Johnston, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We search for coincident gravitational wave signals from inspiralling neutron star binaries using LIGO and TAMA300 data taken during early 2003. Using a simple trigger exchange method, we perform an intercollaboration coincidence search during times when TAMA300 and only one of the LIGO sites were operational. We find no evidence of any gravitational wave signals. We place an observational upper limit on the rate of binary neutron star coalescence with component masses between 1 and 3M⊙ of 49 per year per Milky Way equivalent galaxy at a 90% confidence level. The methods developed during this search will find application in …

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Tomographic Approach To Resolving The Distribution Of Lisa Galactic Binaries, Soumya Mohanty, Rajesh K. Nayak Apr 2006

Tomographic Approach To Resolving The Distribution Of Lisa Galactic Binaries, Soumya Mohanty, Rajesh K. Nayak

Physics & Astronomy Faculty Publications

The space based gravitational wave detector LISA (Laser Interferometer Space Antenna) is expected to observe a large population of Galactic white dwarf binaries whose collective signal is likely to dominate instrumental noise at observational frequencies in the range 10−4 to 10−3  Hz. The motion of LISA modulates the signal of each binary in both frequency and amplitude—the exact modulation depending on the source direction and frequency. Starting with the observed response of one LISA interferometer and assuming only Doppler modulation due to the orbital motion of LISA, we show how the distribution of the entire binary population in frequency and …

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Accurate Evolutions Of Orbiting Black-Hole Binaries Without Excision, M. Campanelli, C. O. Lousto, P. Marronetti, Z. Zlochower Mar 2006

Accurate Evolutions Of Orbiting Black-Hole Binaries Without Excision, M. Campanelli, C. O. Lousto, P. Marronetti, Z. Zlochower

Physics & Astronomy Faculty Publications

We present a new algorithm for evolving orbiting black-hole binaries that does not require excision or a corotating shift. Our algorithm is based on a novel technique to handle the singular puncture conformal factor. This system, based on the Baumgarte-Shapiro-Shibata-Nakamura formulation of Einstein’s equations, when used with a ‘‘precollapsed’’ initial lapse, is nonsingular at the start of the evolution and remains nonsingular and stable provided that a good choice is made for the gauge. As a test case, we use this technique to fully evolve orbiting black-hole binaries from near the innermost stable circular orbit regime. We show fourth-order convergence …

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Relativistic Binaries In Globular Clusters, Matthew J. Benacquista Feb 2006

Relativistic Binaries In Globular Clusters, Matthew J. Benacquista

Physics & Astronomy Faculty Publications

The galactic population of globular- cluster's are old, dense star systems, with a typical cluster containing 104 -107 stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or- two compact objects. In this review, we discuss the theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution which lead to relativistic binaries, and …

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The Lazarus Project. Ii. Spacelike Extraction With The Quasi-Kinnersley Tetrad, Manuela Campanelli, Bernard Kelly, Carlos O. Lousto Jan 2006

The Lazarus Project. Ii. Spacelike Extraction With The Quasi-Kinnersley Tetrad, Manuela Campanelli, Bernard Kelly, Carlos O. Lousto

Physics & Astronomy Faculty Publications

The Lazarus project was designed to make the most of limited 3D binary black-hole simulations, through the identification of perturbations at late times, and subsequent evolution of the Weyl scalar Ψ4 via the Teukolsky formulation. Here we report on new developments, employing the concept of the “quasi-Kinnersley” (transverse) frame, valid in the full nonlinear regime, to analyze late-time numerical space-times that should differ only slightly from Kerr. This allows us to extract the essential information about the background Kerr solution, and through this, to identify the radiation present. We explicitly test this procedure with full-numerical evolutions of Bowen-York data for …

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