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Articles 691 - 720 of 832

Full-Text Articles in Astrophysics and Astronomy

First Ligo Search For Gravitational Wave Bursts From Cosmic (Super)Strings, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone Sep 2009

First Ligo Search For Gravitational Wave Bursts From Cosmic (Super)Strings, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone

Physics & Astronomy Faculty Publications

We report on a matched-filter search for gravitational wave bursts from cosmic string cusps using LIGO data from the fourth science run (S4) which took place in February and March 2005. No gravitational waves were detected in 14.9 days of data from times when all three LIGO detectors were operating. We interpret the result in terms of a frequentist upper limit on the rate of gravitational wave bursts and use the limits on the rate to constrain the parameter space (string tension, reconnection probability, and loop sizes) of cosmic string models. Many grand unified theory-scale models (with string tension ��⁢��/��2≈10−6) …

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A Search For Periodic Gravitational Waves From Three Recycled Pulsars Using The Auriga Detector, A. Mion, M. J. Benacquista, M. Kramer, P. P.C. Freire, A. Possenti Sep 2009

A Search For Periodic Gravitational Waves From Three Recycled Pulsars Using The Auriga Detector, A. Mion, M. J. Benacquista, M. Kramer, P. P.C. Freire, A. Possenti

Physics & Astronomy Faculty Publications

Aims.We report on a search for continuous gravitational wave emission from three recycled radio pulsars, performed by using the data of the resonant detector AURIGA. Given the spin rate of the selected targets - the isolated pulsar PSR J1939+2134 and the binary pulsars PSR J0024-7204J and PSR J0218+4232 - the expected frequency of the emitted gravitational waves falls in the high sensitivity range of the detector. Methods.The main topic is the method, meaning that the statistical analysis is performed by implementing a slightly modified version of the Feldman and Cousins Unified Approach. Results.By using ephemerides provided by suitable radio observations …

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Search For Gravitational Wave Ringdowns From Perturbed Black Holes In Ligo S4 Data, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone, Lappoon R. Tang Sep 2009

Search For Gravitational Wave Ringdowns From Perturbed Black Holes In Ligo S4 Data, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone, Lappoon R. Tang

Physics & Astronomy Faculty Publications

According to general relativity a perturbed black hole will settle to a stationary configuration by the emission of gravitational radiation. Such a perturbation will occur, for example, in the coalescence of a black hole binary, following their inspiral and subsequent merger. At late times the waveform is a superposition of quasinormal modes, which we refer to as the ringdown. The dominant mode is expected to be the fundamental mode, l=m=2. Since this is a well-known waveform, matched filtering can be implemented to search for this signal using LIGO data. We present a search for gravitational waves from black hole ringdowns …

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Einstein@Home Search For Periodic Gravitational Waves In Early S5 Ligo Data, B. P. Abbott, R. Abbott, R. Adhikari, Teviet Creighton, Matthew Benacquista, Mario C. Diaz, Soma Mukherjee, Soumya D. Mohanty, Malik Rakhmanov, Joseph D. Romano Aug 2009

Einstein@Home Search For Periodic Gravitational Waves In Early S5 Ligo Data, B. P. Abbott, R. Abbott, R. Adhikari, Teviet Creighton, Matthew Benacquista, Mario C. Diaz, Soma Mukherjee, Soumya D. Mohanty, Malik Rakhmanov, Joseph D. Romano

Physics & Astronomy Faculty Publications

This paper reports on an all-sky search for periodic gravitational waves from sources such as deformed isolated rapidly spinning neutron stars. The analysis uses 840 hours of data from 66 days of the fifth LIGO science run (S5). The data were searched for quasimonochromatic waves with frequencies f in the range from 50 to 1500 Hz, with a linear frequency drift ḟ (measured at the solar system barycenter) in the range -f/τ<ḟ<0.1f/τ, for a minimum spin-down age τ of 1000 years for signals below 400 Hz and 8000 years above 400 Hz. The main computational work of the search was distributed over approximately 100000 computers volunteered by the general public. This large computing power allowed the use of a relatively long coherent integration time of 30 hours while searching a large parameter space. This search extends Einstein@Home's previous search in LIGO S4 data to about 3 times better sensitivity. No statistically significant signals were found. In the 125-225 Hz band, more than 90% of sources with dimensionless gravitational-wave strain tensor amplitude greater than 3×10-24 would have been detected. © 2009 The American Physical Society.

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Observation Of A Kilogram-Scale Oscillator Near Its Quantum Ground State, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Joseph D. Romano Jul 2009

Observation Of A Kilogram-Scale Oscillator Near Its Quantum Ground State, B. P. Abbott, R. Abbott, R. Adhikari, P. Ajith, B. Allen, G. Allen, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Joseph D. Romano

Physics & Astronomy Faculty Publications

We introduce a novel cooling technique capable of approaching the quantum ground state of a kilogram-scale system-an interferometric gravitational wave detector. The detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) operate within a factor of 10 of the standard quantum limit (SQL), providing a displacement sensitivity of 10-18 m in a 100 Hz band centered on 150 Hz. With a new feedback strategy, we dynamically shift the resonant frequency of a 2.7 kg pendulum mode to lie within this optimal band, where its effective temperature falls as low as 1.4μK, and its occupation number reaches about 200 quanta. This work …

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Search For Gravitational Waves From Low Mass Binary Coalescences In The First Year Of Ligo’S S5 Data, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone Jun 2009

Search For Gravitational Waves From Low Mass Binary Coalescences In The First Year Of Ligo’S S5 Data, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone

Physics & Astronomy Faculty Publications

We have searched for gravitational waves from coalescing low mass compact binary systems with a total mass between 2M⊙ and 35M⊙ and a minimum component mass of 1M⊙ using data from the first year of the fifth science run of the three LIGO detectors, operating at design sensitivity. Depending on the mass, we are sensitive to coalescences as far as 150 Mpc from the Earth. No gravitational-wave signals were observed above the expected background. Assuming a population of compact binary objects with a Gaussian mass distribution representing binary neutron star systems, black hole–neutron star binary systems, and binary black hole …

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Tempo2: A New Pulsar Timing Package - Iii. Gravitational Wave Simulation, G. Hobbs, F. Jenet, K. J. Lee, J. P.W. Verbiest, D. Yardley, R. Manchester, A. Lommen, W. Coles, R. Edwards, C. Shettigara Apr 2009

Tempo2: A New Pulsar Timing Package - Iii. Gravitational Wave Simulation, G. Hobbs, F. Jenet, K. J. Lee, J. P.W. Verbiest, D. Yardley, R. Manchester, A. Lommen, W. Coles, R. Edwards, C. Shettigara

Physics & Astronomy Faculty Publications

Analysis of pulsar timing data sets may provide the first direct detection of gravitational waves. This paper, the third in a series describing the mathematical framework implemented into the TEMPO2 pulsar timing package, reports on using TEMPO2 to simulate the timing residuals induced by gravitational waves. The TEMPO2 simulations can be used to provide upper bounds on the amplitude of an isotropic, stochastic, gravitational wave background in our Galaxy and to determine the sensitivity of a given pulsar timing experiment to individual, supermassive, binary black hole systems. © 2009 The Authors. Journal compilation © 2009 RAS.

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Detecting A Stochastic Gravitational-Wave Background: The Overlap Reduction Function, Lee Samuel Finn, Shane L. Larson, Joseph D. Romano Mar 2009

Detecting A Stochastic Gravitational-Wave Background: The Overlap Reduction Function, Lee Samuel Finn, Shane L. Larson, Joseph D. Romano

Physics & Astronomy Faculty Publications

Detection of a gravitational-wave stochastic background via ground or space-based gravitational-wave detectors requires the cross correlation of the response of two or more independent detectors. The cross correlation involves a frequency-dependent factor—the so-called overlap reduction function or HellingsDowns curve—that depends on the relative geometry of each detector pair, i.e., the detector separations and the relative orientation of their antenna patterns (beams). An incorrect formulation of this geometrical factor has appeared in the literature, leading to incorrect conclusions regarding the sensitivity of proposed detectors to a stochastic gravitational-wave background. To rectify these errors and as a reference for future work we …

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Pulsar Timing And Spacetime Curvature, Teviet Creighton, Fredrick A. Jenet, Richard H. Price Mar 2009

Pulsar Timing And Spacetime Curvature, Teviet Creighton, Fredrick A. Jenet, Richard H. Price

Physics & Astronomy Faculty Publications

We analyze the effect of weak field gravitational waves on the timing of pulsars, with particular attention to gauge invariance, that is, to the effects that are independent of the choice of coordinates. We find (1) the Doppler shift cannot be separated into gauge invariant gravitational wave and kinetic contributions; (2) a gauge invariant separation can be made for the time derivative of the Doppler shift in which the gravitational wave contribution is directly related to the Riemann tensor, and the kinetic contribution is that for special relativity; (3) the gaugedependent effects in the Doppler shift play no role in …

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The Contribution Of Halo White Dwarf Binaries To The Laser Interferometer Space Antenna Signal, Ashley J. Ruiter, Krzysztof Belczynski, Matthew Benacquista, Kelly Holley-Bockelmann Mar 2009

The Contribution Of Halo White Dwarf Binaries To The Laser Interferometer Space Antenna Signal, Ashley J. Ruiter, Krzysztof Belczynski, Matthew Benacquista, Kelly Holley-Bockelmann

Physics & Astronomy Faculty Publications

Galactic double white dwarfs were postulated as a source of confusion limited noise for the Laser Interferometer Space Antenna (LISA), the future space-based gravitational wave observatory. Until very recently, the Galactic population consisted of a relatively well-studied disk population, a somewhat studied smaller bulge population and a mostly unknown, but potentially large halo population. It has been argued that the halo population may produce a signal that is much stronger (factor of ∼5 in spectral amplitude) than the disk population. However, this surprising result was not based on an actual calculation of a halo white dwarf population, but was derived …

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All-Sky Ligo Search For Periodic Gravitational Waves In The Early Fifth-Science-Run Data, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano Mar 2009

All-Sky Ligo Search For Periodic Gravitational Waves In The Early Fifth-Science-Run Data, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, R. Grosso, K. Hayama, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano

Physics & Astronomy Faculty Publications

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50–1100 Hz and with the frequency’s time derivative in the range −5×10−9–0  Hz s−1. Data from the first eight months of the fifth LIGO science run (S5) have been used in this search, which is based on a semicoherent method (PowerFlux) of summing strain power. Observing no evidence of periodic gravitational radiation, we report 95% confidence-level upper limits on radiation emitted by any unknown isolated rotating neutron stars within the search range. Strain limits below 10−24 are obtained over a 200-Hz band, …

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Einstein@Home Search For Periodic Gravitational Waves In Ligo S4 Data, B. Abbott, R. Abbott, R. Adhikari, Teviet Creighton, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Joseph D. Romano Jan 2009

Einstein@Home Search For Periodic Gravitational Waves In Ligo S4 Data, B. Abbott, R. Abbott, R. Adhikari, Teviet Creighton, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Joseph D. Romano

Physics & Astronomy Faculty Publications

A search for periodic gravitational waves, from sources such as isolated rapidly spinning neutron stars, was carried out using 510 h of data from the fourth LIGO science run (S4). The search was for quasimonochromatic waves in the frequency range from 50 to 1500 Hz, with a linear frequency drift ˙�� (measured at the solar system barycenter) in the range −��/��<˙��<0.1⁢��/��, where the minimum spin-down age �� was 1000 yr for signals below 300 Hz and 10 000 yr above 300 Hz. The main computational work of the search was distributed over approximately 100 000 computers volunteered by the general public. This large computing power allowed the use of a relatively long coherent integration time of 30 h, despite the large parameter space searched. No statistically significant signals were found. The sensitivity of the search is estimated, along with the fraction of parameter space that was vetoed because of contamination by instrumental artifacts. In the 100 to 200 Hz band, more than 90% of sources with dimensionless gravitational-wave strain amplitude greater than 10−23 would have been detected.

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Arecibo Pulsar Survey Using Alpha: Probing Radio Pulsar Intermittency And Transients, J. S. Deneva, J. M. Cordes, M. A. Mclaughlin, D. J. Nice, D. R. Lorimer, F. Crawford, N. D.R. Bhat, F. Camilo, Fredrick A. Jenet, J. Van Leeuwen Jan 2009

Arecibo Pulsar Survey Using Alpha: Probing Radio Pulsar Intermittency And Transients, J. S. Deneva, J. M. Cordes, M. A. Mclaughlin, D. J. Nice, D. R. Lorimer, F. Crawford, N. D.R. Bhat, F. Camilo, Fredrick A. Jenet, J. Van Leeuwen

Physics & Astronomy Faculty Publications

We present radio transient search algorithms, results, and statistics from the ongoing Arecibo Pulsar ALFA (PALFA) survey of the Galactic plane. We have discovered seven objects through a search for isolated dispersed pulses. All of these objects are Galactic and have measured periods between 0.4 and 4.7 s. One of the new discoveries has a duty cycle of 0.01%, smaller than that of any other radio pulsar. We discuss the impact of selection effects on the detectability and classification of intermittent sources, and compare the efficiencies of periodicity and single-pulse (SP) searches for various pulsar classes. For some cases we …

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Stellar Population Models And Individual Element Abundances. Ii. Stellar Spectra And Integrated Light Models, Hyun Chul Lee, Guy Worthey, Aaron Dotter, Brian Chaboyer, Darko Jevremović, E. Baron, Michael M. Briley, Jason W. Ferguson, Paula Coelho, Scott C. Trager Jan 2009

Stellar Population Models And Individual Element Abundances. Ii. Stellar Spectra And Integrated Light Models, Hyun Chul Lee, Guy Worthey, Aaron Dotter, Brian Chaboyer, Darko Jevremović, E. Baron, Michael M. Briley, Jason W. Ferguson, Paula Coelho, Scott C. Trager

Physics & Astronomy Faculty Publications

The first paper in this series explored the effects of altering the chemical mixture of the stellar population on an element-by-element basis on stellar evolutionary tracks and isochrones to the end of the red giant branch. This paper extends the discussion by incorporating the fully consistent synthetic stellar spectra with those isochrone models in predicting integrated colors, Lick indices, and synthetic spectra. Older populations display element ratio effects in their spectra at higher amplitude than younger populations. In addition, spectral effects in the photospheres of stars tend to dominate over effects from isochrone temperatures and lifetimes, but, further, the isochrone-based …

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Xafs Debye-Waller Factors For Deformed Hemes And Metal Substituted Hemes, Nicholas Dimakis, T. Mion, C. Ramirez, G. Bunker Jan 2009

Xafs Debye-Waller Factors For Deformed Hemes And Metal Substituted Hemes, Nicholas Dimakis, T. Mion, C. Ramirez, G. Bunker

Physics & Astronomy Faculty Publications

We present an efficient and accurate method for calculating XAFS Debye-Waller factors for deformed active sites of hemoproteins and metal substituted hemes. Based on the Normal Coordinate Structural Decomposition scheme, the deformation of the porphyrin macrocycle is expressed as a linear combination of the normal modes of the planar species. In our approach, we identify the modes that contribute most to the deformation. Small metal-porphyrin structures which match the macrocycle structural deformation of the deformed hemoprotein site are used to calculate the Debye-Waller parameters at sample's temperature. The Debye-Waller factors are directly obtained by calculating the normal mode spectrum of …

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Strong Field Effects On Pulsar Arrival Times: General Orientations, Yan Wang, Teviet Creighton, Richard H. Price, Fredrick A. Jenet Jan 2009

Strong Field Effects On Pulsar Arrival Times: General Orientations, Yan Wang, Teviet Creighton, Richard H. Price, Fredrick A. Jenet

Physics & Astronomy Faculty Publications

A pulsar beam passing close to a black hole can provide a probe of very strong gravitational fields even if the pulsar itself is not in a strong field region. In the case that the spin of the hole can be ignored, we have previously shown that all strong field effects on the beam can be understood in terms of two \"universal\" functions: F(φin) and T(φin) of the angle of beam emission φin; these functions are universal in that they depend only on a single parameter, the pulsar/black hole distance from which the beam is emitted. Here we apply this …

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Stacked Search For Gravitational Waves From The 2006 Sgr 1900+14 Storm, B. P. Abbott, R. Abbott, R. Adhikari, Teviet Creighton, Matthew Benacquista, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano Jan 2009

Stacked Search For Gravitational Waves From The 2006 Sgr 1900+14 Storm, B. P. Abbott, R. Abbott, R. Adhikari, Teviet Creighton, Matthew Benacquista, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano

Physics & Astronomy Faculty Publications

We present the results of a LIGO search for short-duration gravitational waves (GWs) associated with the 2006 March 29 SGR 1900+14 storm. A new search method is used, \"stacking\" the GW data around the times of individual soft-gamma bursts in the storm to enhance sensitivity for models in which multiple bursts are accompanied by GW emission. We assume that variation in the time difference between burst electromagnetic emission and potential burst GW emission is small relative to the GW signal duration, and we time-align GW excess power time-frequency tilings containing individual burst triggers to their corresponding electromagnetic emissions. We use …

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Strong Field Effects On Pulsar Arrival Times: Circular Orbits And Equatorial Beams, Yan Wang, Fredrick Jenet, Teviet Creighton, Richard H. Price Jan 2009

Strong Field Effects On Pulsar Arrival Times: Circular Orbits And Equatorial Beams, Yan Wang, Fredrick Jenet, Teviet Creighton, Richard H. Price

Physics & Astronomy Faculty Publications

If a pulsar orbits a supermassive black hole, the timing of pulses that pass close to the hole will show a variety of strong field effects. To compute the intensity and timing of pulses that have passed close to a nonrotating black hole, we introduce here a simple formalism based on two \"universal functions,\" one for the bending of photon trajectories and the other for the photon travel time on these trajectories. We apply this simple formalism to the case of a pulsar in circular orbit that beams its pulses into the orbital plane. In addition to the \"primary\" pulses …

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Search For Gravitational Waves From Low Mass Compact Binary Coalescence In 186 Days Of Ligo’S Fifth Science Run, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone, Lappoon R. Tang Jan 2009

Search For Gravitational Waves From Low Mass Compact Binary Coalescence In 186 Days Of Ligo’S Fifth Science Run, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, K. Hayama, H. Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone, Lappoon R. Tang

Physics & Astronomy Faculty Publications

We report on a search for gravitational waves from coalescing compact binaries, of total mass between 2 and 35M⊙, using LIGO observations between November 14, 2006 and May 18, 2007. No gravitational-wave signals were detected. We report upper limits on the rate of compact binary coalescence as a function of total mass. The LIGO cumulative 90%-confidence rate upper limits of the binary coalescence of neutron stars, black holes and black hole-neutron star systems are 1.4×10−2, 7.3×10−4 and 3.6×10−3  yr−1 L−110, respectively, where L10 is 1010 times the blue solar luminosity.

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Search For Gravitational-Wave Bursts In The First Year Of The Fifth Ligo Science Run, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, Hansheng Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano Jan 2009

Search For Gravitational-Wave Bursts In The First Year Of The Fifth Ligo Science Run, B. P. Abbott, R. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, Hansheng Lei, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano

Physics & Astronomy Faculty Publications

We present the results obtained from an all-sky search for gravitational-wave (GW) bursts in the 64–2000 Hz frequency range in data collected by the LIGO detectors during the first year (November 2005—November 2006) of their fifth science run. The total analyzed live time was 268.6 days. Multiple hierarchical data analysis methods were invoked in this search. The overall sensitivity expressed in terms of the root-sum-square (rss) strain amplitude hrss for gravitational-wave bursts with various morphologies was in the range of 6×10−22  Hz−1/2 to a few×10−21  Hz−1/2. No GW signals were observed and a frequentist upper limit of 3.75 events per …

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Uv-Vis Investigations On Ion Beam Irradiated Polycarbonate, Mircea Chipara, Dorina M. Chipara Nov 2008

Uv-Vis Investigations On Ion Beam Irradiated Polycarbonate, Mircea Chipara, Dorina M. Chipara

Physics & Astronomy Faculty Publications

UV-VIS investigations on polycarbonate irradiated with accelerated U ions are reported. The experimental data are consistent with the decrease of the energy gap due to irradiation and indicate the formation of isolated conjugated structures. The relatively weak decrease of the energy gap and the shape of the electron spin resonance lines indicate that the conjugated structures are isolated within the polymeric matrix. published: 8 November, 2008.

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Search For Gravitational-Wave Bursts From Soft Gamma Repeaters, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, K. Hayama, Soma Mukherjee, Soumya Mohanty, Joseph D. Romano, Robert Stone Nov 2008

Search For Gravitational-Wave Bursts From Soft Gamma Repeaters, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, K. Hayama, Soma Mukherjee, Soumya Mohanty, Joseph D. Romano, Robert Stone

Physics & Astronomy Faculty Publications

We present a LIGO search for short-duration gravitational waves (GWs) associated with soft gamma ray repeater (SGR) bursts. This is the first search sensitive to neutron star f modes, usually considered the most efficient GW emitting modes. We find no evidence of GWs associated with any SGR burst in a sample consisting of the 27 Dec. 2004 giant flare from SGR 1806−20 and 190 lesser events from SGR 1806−20 and SGR 1900+14. The unprecedented sensitivity of the detectors allows us to set the most stringent limits on transient GW amplitudes published to date. We find upper limit estimates on the …

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Pulsar Timing As A Probe Of Non-Einsteinlan Polarizations Of Gravitational Waves, K. J. Lee, F. A. Jenet, Richard H. Price Oct 2008

Pulsar Timing As A Probe Of Non-Einsteinlan Polarizations Of Gravitational Waves, K. J. Lee, F. A. Jenet, Richard H. Price

Physics & Astronomy Faculty Publications

Einstein's theory of gravity predicts waves of the distortion of spacetime with two degrees of polarization; alternative theories predict more polarizations, up to a maximum of six. Although laser interferometric gravity wave detectors can be used to search for at least some of the non-Einsteinian polarizations, their configuration is not optimal for the task. By contrast, the angular distribution of pulsars in the sky makes pulsar timing a flexible tool for detecting all polarizations. We give here an analysis of the sensitivity of pulsar timing to an isotropic stochastic gravitational wave background of waves with non-Einsteinian polarizations and conclude that …

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A Teaching Intervention To Increase Achievement Of Hispanic Nonscience Majors Taking Physical Science Courses, G. Herold Poelzer, Liang Zeng Sep 2008

A Teaching Intervention To Increase Achievement Of Hispanic Nonscience Majors Taking Physical Science Courses, G. Herold Poelzer, Liang Zeng

Physics & Astronomy Faculty Publications

This quasi-experimental pilot study of nonscience majors taking a physical science course at a university in South Texas was conducted on Hispanic undergraduate students, and is theory based--an application of attribution theory. That the treatment group outperformed the comparison group provides evidence of the positive effect of having students reflect on controllable reasons for their grades and on their subsequent planning of strategies to maintain or improve those grades. (Contains 1 table and 2 figures.)

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Implications For The Origin Of Grb 070201 From Ligo Observations, B. Abbott, R. Abbott, R. Adhikari, J. Agresti, P. Ajith, Mario C. Diaz, Roberto Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Jul 2008

Implications For The Origin Of Grb 070201 From Ligo Observations, B. Abbott, R. Abbott, R. Adhikari, J. Agresti, P. Ajith, Mario C. Diaz, Roberto Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We analyzed the available LIGO data coincident with GRB 070201, a short-duration, hard-spectrum γ-ray burst (GRB) whose electromagnetically determined sky position is coincident with the spiral arms of the Andromeda galaxy (M31). Possible progenitors of such short, hard GRBs include mergers of neutron stars or a neutron star and a black hole, or soft γ-ray repeater (SGR) flares. These events can be accompanied by gravitational-wave emission. No plausible gravitational-wave candidates were found within a 180 s long window around the time of GRB 070201. This result implies that a compact binary progenitor of GRB 070201, with masses in the range …

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Arecibo H I Absorption Measurements Of Pulsars And The Electron Density At Intermediate Longitudes In The First Galactic Quadrant, J. M. Weisberg, S. Stanimirović, K. Xilouris, A. Hedden, A. De La Fuente, S. B. Anderson, F. A. Jenet Feb 2008

Arecibo H I Absorption Measurements Of Pulsars And The Electron Density At Intermediate Longitudes In The First Galactic Quadrant, J. M. Weisberg, S. Stanimirović, K. Xilouris, A. Hedden, A. De La Fuente, S. B. Anderson, F. A. Jenet

Physics & Astronomy Faculty Publications

We have used the Arecibo telescope to measure the H I absorption spectra of eight pulsars. We show how kinematic distance measurements depend on the values of the Galactic constants R0 and Θ0, and we select our preferred current values from the literature. We then derive kinematic distances for the low-latitude pulsars in our sample and electron densities along their lines of sight. We combine these measurements with all others in the inner Galactic plane visible from Arecibo to study the electron density in this region. The electron density in the interarm range 48° < l < 70° is 0.017-0.007+0.012(68% c.1.) cm-3. This is 0.75-0.22+0.49(68% c.1.) of the value calculated by the Galactic electron density model of Cordes & Lazio. The model agrees more closely with electron density measurements toward Arecibo pulsars lying closer to the Galactic center, at 30° < l < 48°. Our analysis leads to the best current estimate of the distance of the relativistic binary pulsar B1913+16: d = 9.0 ± 3 kpc We use the high-latitude pulsars to search for small-scale structure in the interstellar hydrogen observed in absorption over multiple epochs. PSR B0301+19 exhibited significant changes in its absorption spectrum over 22 yr, indicating H I structure on a ∼500 AU scale. © 2008. The American Astronomical Society. All rights reserved.

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Search For Gravitational Waves From Binary Inspirals In S3 And S4 Ligo Data, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Jan 2008

Search For Gravitational Waves From Binary Inspirals In S3 And S4 Ligo Data, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We report on a search for gravitational waves from the coalescence of compact binaries during the third and fourth LIGO science runs. The search focused on gravitational waves generated during the inspiral phase of the binary evolution. In our analysis, we considered three categories of compact binary systems, ordered by mass: (i) primordial black hole binaries with masses in the range 0.35M⊙

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All-Sky Search For Periodic Gravitational Waves In Ligo S4 Data, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Jan 2008

All-Sky Search For Periodic Gravitational Waves In Ligo S4 Data, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We report on an all-sky search with the LIGO detectors for periodic gravitational waves in the frequency range 50–1000 Hz and with the frequency’s time derivative in the range −1×10−8  Hz s−1 to zero. Data from the fourth LIGO science run (S4) have been used in this search. Three different semicoherent methods of transforming and summing strain power from short Fourier transforms (SFTs) of the calibrated data have been used. The first, known as StackSlide, averages normalized power from each SFT. A “weighted Hough” scheme is also developed and used, which also allows for a multi-interferometer search. The third method, …

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Psr J1856+0245: Arecibo Discovery Of A Young Energetic Pulsar Coincident With The Tev G-Ray Source Hess J1857+026, J. W.T. Hessels, D. J. Nice, B. M. Gaensler, V. M. Kaspi, D. R. Lorimer, D. J. Champion, A. G. Lyne, M. Kramer, J. M. Cordes, P. C.C. Freire, Fredrick A. Jenet Jan 2008

Psr J1856+0245: Arecibo Discovery Of A Young Energetic Pulsar Coincident With The Tev G-Ray Source Hess J1857+026, J. W.T. Hessels, D. J. Nice, B. M. Gaensler, V. M. Kaspi, D. R. Lorimer, D. J. Champion, A. G. Lyne, M. Kramer, J. M. Cordes, P. C.C. Freire, Fredrick A. Jenet

Physics & Astronomy Faculty Publications

We present the discovery of the Vela-like radio pulsar J1856+0245 in the Arecibo PALFA survey. PSR J1856+0245 has a spin period of 81 ms, a characteristic age of 21 kyr, and a spin-down luminosity Ä– p 4.6 x 10 36 ergs s-1. It is positionally coincident with the TeV γ-ray source HESS J1857+026, which has no other known counterparts. Young, energetic pulsars create wind nebulae, and more than a dozen pulsar wind nebulae have been associated with very high energy (100 GeV-100 TeV) γ-ray sources discovered with the HESS telescope. The γ-ray emission seen from HESS J1857+026 is potentially produced …

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Kinetics And Thermodynamics Of Salt-Dependent T7 Gene 2.5 Protein Binding To Single- And Double-Stranded Dna., Leila Shokri, Boriana Marintcheva, Mootaz Eldib, Andreas Hanke, Ioulia Rouzina, Mark C. Williams Jan 2008

Kinetics And Thermodynamics Of Salt-Dependent T7 Gene 2.5 Protein Binding To Single- And Double-Stranded Dna., Leila Shokri, Boriana Marintcheva, Mootaz Eldib, Andreas Hanke, Ioulia Rouzina, Mark C. Williams

Physics & Astronomy Faculty Publications

Bacteriophage T7 gene 2.5 protein (gp2.5) is a single-stranded DNA (ssDNA)-binding protein that has essential roles in DNA replication, recombination and repair. However, it differs from other ssDNA-binding proteins by its weaker binding to ssDNA and lack of cooperative ssDNA binding. By studying the rate-dependent DNA melting force in the presence of gp2.5 and its deletion mutant lacking 26 C-terminal residues, we probe the kinetics and thermodynamics of gp2.5 binding to ssDNA and double-stranded DNA (dsDNA). These force measurements allow us to determine the binding rate of both proteins to ssDNA, as well as their equilibrium association constants to dsDNA. …

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